Bill Bryson《A Short History of Nearly Everything》23-29

part v   life itself

23    THE RICHNESS OF BEING

here and there in the natural history museum in london, built into recesses along theunderlit corridors or standing between glass cases of minerals and ostrich eggs and a centuryor so of other productive clutter, are secret doors—at least secret in the sense that there isnothing about them to attract the visitor’s notice. occasionally you might see someone withthe distracted manner and interestingly willful hair that mark the scholar emerge from one ofthe doors and hasten down a corridor, probably to disappear through another door a littlefurther on, but this is a relatively rare event. for the most part the doors stay shut, giving nohint that beyond them exists another—a parallel—natural history museum as vast as, and inmany ways more wonderful than, the one the public knows and adores.

the natural history museum contains some seventy million objects from every realm oflife and every corner of the planet, with another hundred thousand or so added to thecollection each year, but it is really only behind the scenes that you get a sense of what atreasure house this is. in cupboards and cabinets and long rooms full of close-packed shelvesare kept tens of thousands of pickled animals in bottles, millions of insects pinned to squaresof card, drawers of shiny mollusks, bones of dinosaurs, skulls of early humans, endlessfolders of neatly pressed plants. it is a little like wandering through darwin’s brain. the spiritroom alone holds fifteen miles of shelving containing jar upon jar of animals preserved inmethylated spirit.

back here are specimens collected by joseph banks in australia, alexander von humboldtin amazonia, darwin on the beagle voyage, and much else that is either very rare orhistorically important or both. many people would love to get their hands on these things. afew actually have. in 1954 the museum acquired an outstanding ornithological collection fromthe estate of a devoted collector named richard meinertzhagen, author of birds of arabia,among other scholarly works. meinertzhagen had been a faithful attendee of the museum foryears, coming almost daily to take notes for the production of his books and monographs.

when the crates arrived, the curators excitedly jimmied them open to see what they had beenleft and were surprised, to put it mildly, to discover that a very large number of specimensbore the museum’s own labels. mr. meinertzhagen, it turned out, had been helping himself totheir collections for years. it also explained his habit of wearing a large overcoat even duringwarm weather.

a few years later a charming old regular in the mollusks department—“quite a distinguishedgentleman,” i was told—was caught inserting valued seashells into the hollow legs of hiszimmer frame.

“i don’t suppose there’s anything in here that somebody somewhere doesn’t covet,”

richard fortey said with a thoughtful air as he gave me a tour of the beguiling world that isthe behind-the-scenes part of the museum. we wandered through a confusion of departmentswhere people sat at large tables doing intent, investigative things with arthropods and palm
fronds and boxes of yellowed bones. everywhere there was an air of unhurried thoroughness,of people being engaged in a gigantic endeavor that could never be completed and mustn’t berushed. in 1967, i had read, the museum issued its report on the john murray expedition, anindian ocean survey, forty-four years after the expedition had concluded. this is a worldwhere things move at their own pace, including a tiny lift fortey and i shared with a scholarlylooking elderly man with whom fortey chatted genially and familiarly as we proceededupwards at about the rate that sediments are laid down.

when the man departed, fortey said to me: “that was a very nice chap named normanwho’s spent forty-two years studying one species of plant, st. john’s wort. he retired in 1989,but he still comes in every week.”

“how do you spend forty-two years on one species of plant?” i asked.

“it’s remarkable, isn’t it?” fortey agreed. he thought for a moment. “he’s very thoroughapparently.” the lift door opened to reveal a bricked-over opening. fortey lookedconfounded. “that’s very strange,” he said. “that used to be botany back there.” he puncheda button for another floor, and we found our way at length to botany by means of backstaircases and discreet trespass through yet more departments where investigators toiledlovingly over once-living objects. and so it was that i was introduced to len ellis and thequiet world of bryophytes—mosses to the rest of us.

when emerson poetically noted that mosses favor the north sides of trees (“the moss uponthe forest bark, was pole-star when the night was dark”) he really meant lichens, for in thenineteenth century mosses and lichens weren’t distinguished. true mosses aren’t actuallyfussy about where they grow, so they are no good as natural compasses. in fact, mosses aren’tactually much good for anything. “perhaps no great group of plants has so few uses,commercial or economic, as the mosses,” wrote henry s. conard, perhaps just a touch sadly,in how to know the mosses and liverworts, published in 1956 and still to be found on manylibrary shelves as almost the only attempt to popularize the subject.

they are, however, prolific. even with lichens removed, bryophytes is a busy realm, withover ten thousand species contained within some seven hundred genera. the plump andstately moss flora of britain and ireland by a. j. e. smith runs to seven hundred pages, andbritain and ireland are by no means outstandingly mossy places. “the tropics are where youfind the variety,” len ellis told me. a quiet, spare man, he has been at the natural historymuseum for twenty-seven years and curator of the department since 1990. “you can go outinto a place like the rain forests of malaysia and find new varieties with relative ease. i didthat myself not long ago. i looked down and there was a species that had never beenrecorded.”

“so we don’t know how many species are still to be discovered?”

“oh, no. no idea.”

you might not think there would be that many people in the world prepared to devotelifetimes to the study of something so inescapably low key, but in fact moss people number inthe hundreds and they feel very strongly about their subject. “oh, yes,” ellis told me, “themeetings can get very lively at times.”

i asked him for an example of controversy.

“well, here’s one inflicted on us by one of your countrymen,” he said, smiling lightly, andopened a hefty reference work containing illustrations of mosses whose most notablecharacteristic to the uninstructed eye was their uncanny similarity one to another. “that,” hesaid, tapping a moss, “used to be one genus, drepanocladus. now it’s been reorganized intothree: drepanocladus, wamstorfia, and hamatacoulis.”

“and did that lead to blows?” i asked perhaps a touch hopefully.

“well, it made sense. it made perfect sense. but it meant a lot of reordering of collectionsand it put all the books out of date for a time, so there was a bit of, you know, grumbling.”

mosses offer mysteries as well, he told me. one famous case—famous to moss peopleanyway—involved a retiring type called hyophila stanfordensis, which was discovered on thecampus of stanford university in california and later also found growing beside a path incornwall, on the southwest tip of england, but has never been encountered anywhere inbetween. how it came to exist in two such unconnected locations is anybody’s guess. “it’snow known as hennediella stanfordensis,” ellis said. “another revision.”

we nodded thoughtfully.

when a new moss is found it must be compared with all other mosses to make sure that ithasn’t been recorded already. then a formal description must be written and illustrationsprepared and the result published in a respectable journal. the whole process seldom takesless than six months. the twentieth century was not a great age for moss taxonomy. much ofthe century’s work was devoted to untangling the confusions and duplications left behind bythe nineteenth century.

that was the golden age of moss collecting. (you may recall that charles lyell’s fatherwas a great moss man.) one aptly named englishman, george hunt, hunted british mosses soassiduously that he probably contributed to the extinction of several species. but it is thanksto such efforts that len ellis’s collection is one of the world’s most comprehensive. all780,000 of his specimens are pressed into large folded sheets of heavy paper, some very oldand covered with spidery victorian script. some, for all we knew, might have been in thehand of robert brown, the great victorian botanist, unveiler of brownian motion and thenucleus of cells, who founded and ran the museum’s botany department for its first thirty-oneyears until his death in 1858. all the specimens are kept in lustrous old mahogany cabinets sostrikingly fine that i remarked upon them.

“oh, those were sir joseph banks’s, from his house in soho square,” ellis said casually, asif identifying a recent purchase from ikea. “he had them built to hold his specimens from theendeavour voyage.” he regarded the cabinets thoughtfully, as if for the first time in a longwhile. “i don’t know howwe ended up with them in bryology,” he added.

this was an amazing disclosure. joseph banks was england’s greatest botanist, and theendeavour voyage—that is the one on which captain cook charted the 1769 transit of venusand claimed australia for the crown, among rather a lot else—was the greatest botanicalexpedition in history. banks paid ￡10,000, about $1 million in today’s money, to bringhimself and a party of nine others—a naturalist, a secretary, three artists, and four servants—on the three-year adventure around the world. goodness knows what the bluff captain cook
made of such a velvety and pampered assemblage, but he seems to have liked banks wellenough and could not but admire his talents in botany—a feeling shared by posterity.

never before or since has a botanical party enjoyed greater triumphs. partly it was becausethe voyage took in so many new or little-known places—tierra del fuego, tahiti, newzealand, australia, new guinea—but mostly it was because banks was such an astute andinventive collector. even when unable to go ashore at rio de janeiro because of a quarantine,he sifted through a bale of fodder sent for the ship’s livestock and made new discoveries.

nothing, it seems, escaped his notice. altogether he brought back thirty thousand plantspecimens, including fourteen hundred not seen before—enough to increase by about aquarter the number of known plants in the world.

but banks’s grand cache was only part of the total haul in what was an almost absurdlyacquisitive age. plant collecting in the eighteenth century became a kind of internationalmania. glory and wealth alike awaited those who could find new species, and botanists andadventurers went to the most incredible lengths to satisfy the world’s craving for horticulturalnovelty. thomas nuttall, the man who named the wisteria after caspar wistar, came toamerica as an uneducated printer but discovered a passion for plants and walked halfwayacross the country and back again, collecting hundreds of growing things never seen before.

john fraser, for whom is named the fraser fir, spent years in the wilderness collecting onbehalf of catherine the great and emerged at length to find that russia had a new czar whothought he was mad and refused to honor his contract. fraser took everything to chelsea,where he opened a nursery and made a handsome living selling rhododendrons, azaleas,magnolias, virginia creepers, asters, and other colonial exotica to a delighted english gentry.

huge sums could be made with the right finds. john lyon, an amateur botanist, spent twohard and dangerous years collecting specimens, but cleared almost $200,000 in today’smoney for his efforts. many, however, just did it for the love of botany. nuttall gave most ofwhat he found to the liverpool botanic gardens. eventually he became director of harvard’sbotanic garden and author of the encyclopedicgenera of north american plants (which henot only wrote but also largely typeset).

and that was just plants. there was also all the fauna of the new worlds—kangaroos, kiwis,raccoons, bobcats, mosquitoes, and other curious forms beyond imagining. the volume of lifeon earth was seemingly infinite, as jonathan swift noted in some famous lines:

so, naturalists observe, a fleahath smaller fleas that on him prey;and these have smaller still to bite ’em;and so proceed ad infinitum.

all this new information needed to be filed, ordered, and compared with what was known.

the world was desperate for a workable system of classification. fortunately there was a manin sweden who stood ready to provide it.

his name was carl linné (later changed, with permission, to the more aristocraticvonlinné), but he is remembered now by the latinized form carolus linnaeus. he was born in1707 in the village of r?shult in southern sweden, the son of a poor but ambitious lutherancurate, and was such a sluggish student that his exasperated father apprenticed him (or, by
some accounts, nearly apprenticed him) to a cobbler. appalled at the prospect of spending alifetime banging tacks into leather, young linné begged for another chance, which wasgranted, and he never thereafter wavered from academic distinction. he studied medicine insweden and holland, though his passion became the natural world. in the early 1730s, still inhis twenties, he began to produce catalogues of the world’s plant and animal species, using asystem of his own devising, and gradually his fame grew.

rarely has a man been more comfortable with his own greatness. he spent much of hisleisure time penning long and flattering portraits of himself, declaring that there had never“been a greater botanist or zoologist,” and that his system of classification was “the greatestachievement in the realm of science.” modestly he suggested that his gravestone should bearthe inscription princeps botanicorum, “prince of botanists.” it was never wise to question hisgenerous self-assessments. those who did so were apt to find they had weeds named afterthem.

linnaeus’s other striking quality was an abiding—at times, one might say, a feverish—preoccupation with sex. he was particularly struck by the similarity between certain bivalvesand the female pudenda. to the parts of one species of clam he gave the names vulva, labia,pubes, anus, and hymen. he grouped plants by the nature of their reproductive organs andendowed them with an arrestingly anthropomorphic amorousness. his descriptions of flowersand their behavior are full of references to “promiscuous intercourse,” “barren concubines,”

and “the bridal bed.” in spring, he wrote in one oft-quoted passage:

love comes even to the plants. males and females . . . hold their nuptials . . .

showing by their sexual organs which are males, which females. the flowers’

leaves serve as a bridal bed, which the creator has so gloriously arranged, adornedwith such noble bed curtains, and perfumed with so many soft scents that thebridegroom with his bride might there celebrate their nuptials with so much thegreater solemnity. when the bed has thus been made ready, then is the time for thebridegroom to embrace his beloved bride and surrender himself to her.

he named one genus of plants clitoria. not surprisingly, many people thought him strange.

but his system of classification was irresistible. before linnaeus, plants were given namesthat were expansively descriptive. the common ground cherry was called physalis amnoramosissime ramis angulosis glabris foliis dentoserratis. linnaeus lopped it back to physalisangulata, which name it still uses. the plant world was equally disordered by inconsistenciesof naming. a botanist could not be sure ifrosa sylvestris alba cum rubore, folio glabro wasthe same plant that others called rosa sylvestris inodora seu canina. linnaeus solved thepuzzlement by calling it simply rosa canina. to make these excisions useful and agreeable toall required much more than simply being decisive. it required an instinct—a genius, in fact—for spotting the salient qualities of a species.

the linnaean system is so well established that we can hardly imagine an alternative, butbefore linnaeus, systems of classification were often highly whimsical. animals might becategorized by whether they were wild or domesticated, terrestrial or aquatic, large or small,even whether they were thought handsome and noble or of no consequence. buffon arrangedhis animals by their utility to man. anatomical considerations barely came into it. linnaeus
made it his life’s work to rectify this deficiency by classifying all that was alive according toits physical attributes. taxonomy—which is to say the science of classification—has neverlooked back.

it all took time, of course. the first edition of his great systema naturae in 1735 was justfourteen pages long. but it grew and grew until by the twelfth edition—the last that linnaeuswould live to see—it extended to three volumes and 2,300 pages. in the end he named orrecorded some 13,000 species of plant and animal. other works were more comprehensive—john ray’s three-volume historia generalis plantarum in england, completed a generationearlier, covered no fewer than 18,625 species of plants alone—but what linnaeus had that noone else could touch were consistency, order, simplicity, and timeliness. though his workdates from the 1730s, it didn’t become widely known in england until the 1760s, just in timeto make linnaeus a kind of father figure to british naturalists. nowhere was his systemembraced with greater enthusiasm (which is why, for one thing, the linnaean society has itshome in london and not stockholm).

linnaeus was not flawless. he made room for mythical beasts and “monstrous humans”

whose descriptions he gullibly accepted from seamen and other imaginative travelers. amongthese were a wild man, homo ferus, who walked on all fours and had not yet mastered the artof speech, and homo caudatus, “man with a tail.” but then it was, as we should not forget, analtogether more credulous age. even the great joseph banks took a keen and believing interestin a series of reported sightings of mermaids off the scottish coast at the end of the eighteenthcentury. for the most part, however, linnaeus’s lapses were offset by sound and oftenbrilliant taxonomy. among other accomplishments, he saw that whales belonged with cows,mice, and other common terrestrial animals in the order quadrupedia (later changed tomammalia), which no one had done before.

in the beginning, linnaeus intended only to give each plant a genus name and a number—convolvulus 1, convolvulus 2,and so on—but soon realized that that was unsatisfactory andhit on the binomial arrangement that remains at the heart of the system to this day. theintention originally was to use the binomial system for everything—rocks, minerals, diseases,winds, whatever existed in nature. not everyone embraced the system warmly. many weredisturbed by its tendency toward indelicacy, which was slightly ironic as before linnaeus thecommon names of many plants and animals had been heartily vulgar. the dandelion was longpopularly known as the “pissabed” because of its supposed diuretic properties, and othernames in everyday use included mare’s fart, naked ladies, twitch-ballock, hound’s piss, openarse, and bum-towel. one or two of these earthy appellations may unwittingly survive inenglish yet. the “maidenhair” in maidenhair moss, for instance, does not refer to the hair onthe maiden’s head. at all events, it had long been felt that the natural sciences would beappreciably dignified by a dose of classical renaming, so there was a certain dismay indiscovering that the self-appointed prince of botany had sprinkled his texts with suchdesignations asclitoria, fornicata, andvulva.

over the years many of these were quietly dropped (though not all: the common slipperlimpet still answers on formal occasions to crepidula fornicata) and many other refinementsintroduced as the needs of the natural sciences grew more specialized. in particular the systemwas bolstered by the gradual introduction of additional hierarchies.genus (pluralgenera) andspecies had been employed by naturalists for over a hundred years before linnaeus, andorder, class, and family in their biological senses all came into use in the 1750s and 1760s.

but phylum wasn’t coined until 1876 (by the german ernst haeckel), and family and order
were treated as interchangeable until early in the twentieth century. for a time zoologists usedfamily where botanists placed order, to the occasional confusion of nearly everyone.

1linnaeus had divided the animal world into six categories: mammals, reptiles, birds, fishes,insects, and “vermes,” or worms, for everything that didn’t fit into the first five. from theoutset it was evident that putting lobsters and shrimp into the same category as worms wasunsatisfactory, and various new categories such as mollusca and crustacea were created.

unfortunately these new classifications were not uniformly applied from nation to nation. inan attempt to reestablish order, the british in 1842 proclaimed a new set of rules called thestricklandian code, but the french saw this as highhanded, and the société zoologiquecountered with its own conflicting code. meanwhile, the american ornithological society, forobscure reasons, decided to use the 1758 edition of systema naturae as the basis for all itsnaming, rather than the 1766 edition used elsewhere, which meant that many american birdsspent the nineteenth century logged in different genera from their avian cousins in europe.

not until 1902, at an early meeting of the international congress of zoology, did naturalistsbegin at last to show a spirit of compromise and adopt a universal code.

taxonomy is described sometimes as a science and sometimes as an art, but really it’s abattleground. even today there is more disorder in the system than most people realize. takethe category of the phylum, the division that describes the basic body plans of all organisms.

a few phyla are generally well known, such as mollusks (the home of clams and snails),arthropods (insects and crustaceans), and chordates (us and all other animals with a backboneor protobackbone), though things then move swiftly in the direction of obscurity. among thelatter we might list gnathostomulida (marine worms), cnidaria (jellyfish, medusae,anemones, and corals), and the delicate priapulida (or little “penis worms”). familiar or not,these are elemental divisions. yet there is surprisingly little agreement on how many phylathere are or ought to be. most biologists fix the total at about thirty, but some opt for a numberin the low twenties, while edward o. wilson in the diversity of life puts the number at asurprisingly robust eighty-nine. it depends on where you decide to make your divisions—whether you are a “lumper” or a “splitter,” as they say in the biological world.

at the more workaday level of species, the possibilities for disagreements are even greater.

whether a species of grass should be called aegilops incurva, aegilops incurvata, or aegilopsovata may not be a matter that would stir many nonbotanists to passion, but it can be a sourceof very lively heat in the right quarters. the problem is that there are five thousand species ofgrass and many of them look awfully alike even to people who know grass. in consequence,some species have been found and named at least twenty times, and there are hardly any, itappears, that haven’t been independently identified at least twice. the two-volume manual ofthe grasses of the united states devotes two hundred closely typeset pages to sorting out allthe synonymies, as the biological world refers to its inadvertent but quite commonduplications. and that is just for the grasses of a single country.

to deal with disagreements on the global stage, a body known as the internationalassociation for plant taxonomy arbitrates on questions of priority and duplication. at1to illustrate, humans are in the domain eucarya, in the kingdom animalia, in the phylum chordata, in thesubphylum vertebrata, in the class mammalia, in the order primates, in the family hominidae, in the genus homo,in the species sapiens. (the convention, im informed, is to italicize genus and species names, but not those ofhigher divisions.) some taxonomists employ further subdivisions: tribe, suborder, infraorder, parvorder, andmore.

intervals it hands down decrees, declaring that zauschneria californica (a common plant inrock gardens) is to be known henceforth as epilobium canum or that aglaothamniontenuissimum may now be regarded as conspecific with aglaothamnion byssoides, but notwithaglaothamnion pseudobyssoides. normally these are small matters of tidying up thatattract little notice, but when they touch on beloved garden plants, as they sometimes do,shrieks of outrage inevitably follow. in the late 1980s the common chrysanthemum wasbanished (on apparently sound scientific principles) from the genus of the same name andrelegated to the comparatively drab and undesirable world of the genus dendranthema.

chrysanthemum breeders are a proud and numerous lot, and they protested to the real ifimprobable-sounding committee on spermatophyta. (there are also committees forpteridophyta, bryophyta, and fungi, among others, all reporting to an executive called therapporteur-général; this is truly an institution to cherish.) although the rules of nomenclatureare supposed to be rigidly applied, botanists are not indifferent to sentiment, and in 1995 thedecision was reversed. similar adjudications have saved petunias, euonymus, and a popularspecies of amaryllis from demotion, but not many species of geraniums, which some yearsago were transferred, amid howls, to the genus pelargonium. the disputes are entertaininglysurveyed in charles elliott’s the potting-shed papers.

disputes and reorderings of much the same type can be found in all the other realms of theliving, so keeping an overall tally is not nearly as straightforward a matter as you mightsuppose. in consequence, the rather amazing fact is that we don’t have the faintest idea—“noteven to the nearest order of magnitude,” in the words of edward o. wilson—of the number ofthings that live on our planet. estimates range from 3 million to 200 million. moreextraordinary still, according to a report in the economist, as much as 97 percent of theworld’s plant and animal species may still await discovery.

of the organisms that we do know about, more than 99 in 100 are only sketchilydescribed—“a scientific name, a handful of specimens in a museum, and a few scraps ofdescription in scientific journals” is how wilson describes the state of our knowledge. in thediversity of life, he estimated the number of known species of all types—plants, insects,microbes, algae, everything—at 1.4 million, but added that that was just a guess. otherauthorities have put the number of known species slightly higher, at around 1.5 million to 1.8million, but there is no central registry of these things, so nowhere to check numbers. in short,the remarkable position we find ourselves in is that we don’t actually know what we actuallyknow.

in principle you ought to be able to go to experts in each area of specialization, ask howmany species there are in their fields, then add the totals. many people have in fact done so.

the problem is that seldom do any two come up with matching figures. some sources put thenumber of known types of fungi at 70,000, others at 100,000—nearly half as many again. youcan find confident assertions that the number of described earthworm species is 4,000 andequally confident assertions that the figure is 12,000. for insects, the numbers run from750,000 to 950,000 species. these are, you understand, supposedly the known number ofspecies. for plants, the commonly accepted numbers range from 248,000 to 265,000. thatmay not seem too vast a discrepancy, but it’s more than twenty times the number of floweringplants in the whole of north america.

putting things in order is not the easiest of tasks. in the early 1960s, colin groves of theaustralian national university began a systematic survey of the 250-plus known species ofprimate. oftentimes it turned out that the same species had been described more than once—
sometimes several times—without any of the discoverers realizing that they were dealing withan animal that was already known to science. it took groves four decades to untangleeverything, and that was with a comparatively small group of easily distinguished, generallynoncontroversial creatures. goodness knows what the results would be if anyone attempted asimilar exercise with the planet’s estimated 20,000 types of lichens, 50,000 species ofmollusk, or 400,000-plus beetles.

what is certain is that there is a great deal of life out there, though the actual quantities arenecessarily estimates based on extrapolations—sometimes exceedingly expansiveextrapolations. in a well-known exercise in the 1980s, terry erwin of the smithsonianinstitution saturated a stand of nineteen rain forest trees in panama with an insecticide fog,then collected everything that fell into his nets from the canopy. among his haul (actuallyhauls, since he repeated the experiment seasonally to make sure he caught migrant species)were 1,200 types of beetle. based on the distribution of beetles elsewhere, the number ofother tree species in the forest, the number of forests in the world, the number of other insecttypes, and so on up a long chain of variables, he estimated a figure of 30 million species ofinsects for the entire planet—a figure he later said was too conservative. others using thesame or similar data have come up with figures of 13 million, 80 million, or 100 millioninsect types, underlining the conclusion that however carefully arrived at, such figuresinevitably owe at least as much to supposition as to science.

according to the wall street journal, the world has “about 10,000 active taxonomists”—not a great number when you consider how much there is to be recorded. but, the journaladds, because of the cost (about $2,000 per species) and paperwork, only about fifteenthousand new species of all types are logged per year.

“it’s not a biodiversity crisis, it’s a taxonomist crisis!” barks koen maes, belgian-bornhead of invertebrates at the kenyan national museum in nairobi, whom i met briefly on avisit to the country in the autumn of 2002. there were no specialized taxonomists in thewhole of africa, he told me. “there was one in the ivory coast, but i think he has retired,” hesaid. it takes eight to ten years to train a taxonomist, but none are coming along in africa.

“they are the real fossils,” maes added. he himself was to be let go at the end of the year, hesaid. after seven years in kenya, his contract was not being renewed. “no funds,” maesexplained.

writing in the journal nature last year, the british biologist g. h. godfray noted that thereis a chronic “lack of prestige and resources” for taxonomists everywhere. in consequence,“many species are being described poorly in isolated publications, with no attempt to relate anew taxon2to existing species and classifications.” moreover, much of taxonomists’ time istaken up not with describing new species but simply with sorting out old ones. many,according to godfray, “spend most of their career trying to interpret the work of nineteenth-century systematicists: deconstructing their often inadequate published descriptions orscouring the world’s museums for type material that is often in very poor condition.” godfrayparticularly stresses the absence of attention being paid to the systematizing possibilities ofthe internet. the fact is that taxonomy by and large is still quaintly wedded to paper.

2the formal word for a zoological category, such as phylum or genus. the plural is taxa.

in an attempt to haul things into the modern age, in 2001 kevin kelly, cofounder of wiredmagazine, launched an enterprise called the all species foundation with the aim of findingevery living organism and recording it on a database. the cost of such an exercise has beenestimated at anywhere from $2 billion to as much as $50 billion. as of the spring of 2002, thefoundation had just $1.2 million in funds and four full-time employees. if, as the numberssuggest, we have perhaps 100 million species of insects yet to find, and if our rates ofdiscovery continue at the present pace, we should have a definitive total for insects in a littleover fifteen thousand years. the rest of the animal kingdom may take a little longer.

so why do we know as little as we do? there are nearly as many reasons as there areanimals left to count, but here are a few of the principal causes:

most living things are small and easily overlooked.in practical terms, this is not always abad thing. you might not slumber quite so contentedly if you were aware that your mattress ishome to perhaps two million microscopic mites, which come out in the wee hours to sup onyour sebaceous oils and feast on all those lovely, crunchy flakes of skin that you shed as youdoze and toss. your pillow alone may be home to forty thousand of them. (to them your headis just one large oily bon-bon.) and don’t think a clean pillowcase will make a difference. tosomething on the scale of bed mites, the weave of the tightest human fabric looks like ship’srigging. indeed, if your pillow is six years old—which is apparently about the average age fora pillow—it has been estimated that one-tenth of its weight will be made up of “sloughedskin, living mites, dead mites and mite dung,” to quote the man who did the measuring, dr.

john maunder of the british medical entomology center. (but at least they areyour mites.

think of what you snuggle up with each time you climb into a motel bed.)3these mites havebeen with us since time immemorial, but they weren’t discovered until 1965.

if creatures as intimately associated with us as bed mites escaped our notice until the age ofcolor television, it’s hardly surprising that most of the rest of the small-scale world is barelyknown to us. go out into a woods—any woods at all—bend down and scoop up a handful ofsoil, and you will be holding up to 10 billion bacteria, most of them unknown to science. yoursample will also contain perhaps a million plump yeasts, some 200,000 hairy little fungiknown as molds, perhaps 10,000 protozoans (of which the most familiar is the amoeba), andassorted rotifers, flatworms, roundworms, and other microscopic creatures known collectivelyas cryptozoa. a large portion of these will also be unknown.

the most comprehensive handbook of microorganisms, bergey’s manual of systematicbacteriology, lists about 4,000 types of bacteria. in the 1980s, a pair of norwegian scientists,jostein goks?yr and vigdis torsvik, collected a gram of random soil from a beech forest neartheir lab in bergen and carefully analyzed its bacterial content. they found that this singlesmall sample contained between 4,000 and 5,000 separate bacterial species, more than in thewhole of bergey’s manual. they then traveled to a coastal location a few miles away,scooped up another gram of earth, and found that it contained 4,000 to 5,000 other species. asedward o. wilson observes: “if over 9,000 microbial types exist in two pinches of substratefrom two localities in norway, how many more await discovery in other, radically differenthabitats?” well, according to one estimate, it could be as high as 400 million.

3we are actually getting worse at some matters of hygiene. dr. maunder believes that the move toward low-temperature washing machine detergents has encouraged bugs to proliferate. as he puts it: “if you wash lousyclothing at low temperatures, all you get is cleaner lice.”
we don’t look in the right places. in the diversity of life, wilson describes how onebotanist spent a few days tramping around ten hectares of jungle in borneo and discovered athousand new species of flowering plant—more than are found in the whole of northamerica. the plants weren’t hard to find. it’s just that no one had looked there before. koenmaes of the kenyan national museum told me that he went to one cloud forest, asmountaintop forests are known in kenya, and in a half hour “of not particularly dedicatedlooking” found four new species of millipedes, three representing new genera, and one newspecies of tree. “big tree,” he added, and shaped his arms as if about to dance with a verylarge partner. cloud forests are found on the tops of plateaus and have sometimes beenisolated for millions of years. “they provide the ideal climate for biology and they havehardly been studied,” he said.

overall, tropical rain forests cover only about 6 percent of earth’s surface, but harbor morethan half of its animal life and about two-thirds of its flowering plants, and most of this liferemains unknown to us because too few researchers spend time in them. not incidentally,much of this could be quite valuable. at least 99 percent of flowering plants have never beentested for their medicinal properties. because they can’t flee from predators, plants have hadto contrive chemical defenses, and so are particularly enriched in intriguing compounds. evennow nearly a quarter of all prescribed medicines are derived from just forty plants, withanother 16 percent coming from animals or microbes, so there is a serious risk with everyhectare of forest felled of losing medically vital possibilities. using a method calledcombinatorial chemistry, chemists can generate forty thousand compounds at a time in labs,but these products are random and not uncommonly useless, whereas any natural moleculewill have already passed what the economist calls “the ultimate screening programme: overthree and a half billion years of evolution.”

looking for the unknown isn’t simply a matter of traveling to remote or distant places,however. in his book life: an unauthorised biography, richard fortey notes how oneancient bacterium was found on the wall of a country pub “where men had urinated forgenerations”—a discovery that would seem to involve rare amounts of luckand devotion andpossibly some other quality not specified.

there aren’t enough specialists.the stock of things to be found, examined, and recordedvery much outruns the supply of scientists available to do it. take the hardy and little-knownorganisms known as bdelloid rotifers. these are microscopic animals that can survive almostanything. when conditions are tough, they curl up into a compact shape, switch off theirmetabolism, and wait for better times. in this state, you can drop them into boiling water orfreeze them almost to absolute zero—that is the level where even atoms give up—and, whenthis torment has finished and they are returned to a more pleasing environment, they willuncurl and move on as if nothing has happened. so far, about 500 species have been identified(though other sources say 360), but nobody has any idea, even remotely, how many there maybe altogether. for years almost all that was known about them was thanks to the work of adevoted amateur, a london clerical worker named david bryce who studied them in his sparetime. they can be found all over the world, but you could have all the bdelloid rotifer expertsin the world to dinner and not have to borrow plates from the neighbors.

even something as important and ubiquitous as fungi—and fungi are both—attractscomparatively little notice. fungi are everywhere and come in many forms—as mushrooms,molds, mildews, yeasts, and puffballs, to name but a sampling—and they exist in volumes
that most of us little suspect. gather together all the fungi found in a typical acre of meadowand you would have 2,500 pounds of the stuff. these are not marginal organisms. withoutfungi there would be no potato blights, dutch elm disease, jock itch, or athlete’s foot, but alsono yogurts or beers or cheeses. altogether about 70,000 species of fungi have been identified,but it is thought the number could be as high as 1.8 million. a lot of mycologists work inindustry, making cheeses and yogurts and the like, so it is hard to say how many are activelyinvolved in research, but we can safely take it that there are more species of fungi to be foundthan there are people to find them.

the world is a really big place.we have been gulled by the ease of air travel and otherforms of communication into thinking that the world is not all that big, but at ground level,where researchers must work, it is actually enormous—enormous enough to be full ofsurprises. the okapi, the nearest living relative of the giraffe, is now known to exist insubstantial numbers in the rain forests of zaire—the total population is estimated at perhapsthirty thousand—yet its existence wasn’t even suspected until the twentieth century. the largeflightless new zealand bird called the takahe had been presumed extinct for two hundredyears before being found living in a rugged area of the country’s south island. in 1995 a teamof french and british scientists in tibet, who were lost in a snowstorm in a remote valley,came across a breed of horse, called the riwoche, that had previously been known only fromprehistoric cave drawings. the valley’s inhabitants were astonished to learn that the horse wasconsidered a rarity in the wider world.

some  people  think  even  greater  surprises may await us. “a leading british ethno-biologist,” wrote the economist in 1995, “thinks a megatherium, a sort of giant ground slothwhich may stand as high as a giraffe . . . may lurk in the fastnesses of the amazon basin.”

perhaps significantly, the ethnobiologist wasn’t named; perhaps even more significantly,nothing more has been heard of him or his giant sloth. no one, however, can categorically saythat no such thing is there until every jungly glade has been investigated, and we are a longway from achieving that.

but even if we groomed thousands of fieldworkers and dispatched them to the farthestcorners of the world, it would not be effort enough, for wherever life can be, it is. life’sextraordinary fecundity is amazing, even gratifying, but also problematic. to survey it all, youwould have to turn over every rock, sift through the litter on every forest floor, sieveunimaginable quantities of sand and dirt, climb into every forest canopy, and devise muchmore efficient ways to examine the seas. even then you would overlook whole ecosystems. inthe 1980s, spelunkers entered a deep cave in romania that had been sealed off from theoutside world for a long but unknown period and found thirty-three species of insects andother small creatures—spiders, centipedes, lice—all blind, colorless, and new to science.

they were living off the microbes in the surface scum of pools, which in turn were feeding onhydrogen sulfide from hot springs.

our instinct may be to see the impossibility of tracking everything down as frustrating,dispiriting, perhaps even appalling, but it can just as well be viewed as almost unbearablyexciting. we live on a planet that has a more or less infinite capacity to surprise. whatreasoning person could possibly want it any other way?

what is nearly always most arresting in any ramble through the scattered disciplines ofmodern science is realizing how many people have been willing to devote lifetimes to the
most sumptuously esoteric lines of inquiry. in one of his essays, stephen jay gould notes howa hero of his named henry edward crampton spent fifty years, from 1906 to his death in1956, quietly studying a genus of land snails in polynesia called partula. over and over, yearafter year, crampton measured to the tiniest degree—to eight decimal places—the whorls andarcs and gentle curves of numberless partula, compiling the results into fastidiously detailedtables. a single line of text in a crampton table could represent weeks of measurement andcalculation.

only slightly less devoted, and certainly more unexpected, was alfred c. kinsey, whobecame famous for his studies of human sexuality in the 1940s and 1950s. but before hismind became filled with sex, so to speak, kinsey was an entomologist, and a dogged one atthat. in one expedition lasting two years, he hiked 2,500 miles to assemble a collection of300,000 wasps. how many stings he collected along the way is not, alas, recorded.

something that had been puzzling me was the question of how you assured a chain ofsuccession in these arcane fields. clearly there cannot be many institutions in the world thatrequire or are prepared to support specialists in barnacles or pacific snails. as we parted at thenatural history museum in london, i asked richard fortey how science ensures that whenone person goes there’s someone ready to take his place.

he chuckled rather heartily at my naiveté. “i’m afraid it’s not as if we have substitutessitting on the bench somewhere waiting to be called in to play. when a specialist retires or,even more unfortunately, dies, that can bring a stop to things in that field, sometimes for avery long while.”

“and i suppose that’s why you value someone who spends forty-two years studying asingle species of plant, even if it doesn’t produce anything terribly new?”

“precisely,” he said, “precisely.” and he really seemed to mean it.

24    CELLS

it starts with a single cell. the first cell splits to become two and the two become fourand so on. after just forty-seven doublings, you have ten thousand trillion(10,000,000,000,000,000) cells in your body and are ready to spring forth as a human being.

1and every one of those cells knows exactly what to do to preserve and nurture you from themoment of conception to your last breath.

you have no secrets from your cells. they know far more about you than you do. each onecarries a copy of the complete genetic code—the instruction manual for your body—so itknows not only how to do its job but every other job in the body. never in your life will youhave to remind a cell to keep an eye on its adenosine triphosphate levels or to find a place forthe extra squirt of folic acid that’s just unexpectedly turned up. it will do that for you, andmillions more things besides.

every cell in nature is a thing of wonder. even the simplest are far beyond the limits ofhuman ingenuity. to build the most basic yeast cell, for example, you would have tominiaturize about the same number of components as are found in a boeing 777 jetliner andfit them into a sphere just five microns across; then somehow you would have to persuade thatsphere to reproduce.

but yeast cells are as nothing compared with human cells, which are not just more variedand complicated, but vastly more fascinating because of their complex interactions.

your cells are a country of ten thousand trillion citizens, each devoted in some intensivelyspecific way to your overall well-being. there isn’t a thing they don’t do for you. they letyou feel pleasure and form thoughts. they enable you to stand and stretch and caper. whenyou eat, they extract the nutrients, distribute the energy, and carry off the wastes—all thosethings you learned about in junior high school biology—but they also remember to make youhungry in the first place and reward you with a feeling of well-being afterward so that youwon’t forget to eat again. they keep your hair growing, your ears waxed, your brain quietlypurring. they manage every corner of your being. they will jump to your defense the instantyou are threatened. they will unhesitatingly die for you—billions of them do so daily. andnot once in all your years have you thanked even one of them. so let us take a moment now toregard them with the wonder and appreciation they deserve.

we understand a little of how cells do the things they do—how they lay down fat ormanufacture insulin or engage in many of the other acts necessary to maintain a complicatedentity like yourself—but only a little. you have at least 200,000 different types of protein1actually, quite a lot of cells are lost in the process of development, so the number you emerge with is reallyjust a guess. depending on which source you consult the number can vary by several orders of magnitude. thefigure of ten thousand trillion (or quadrillion) is from margulis and sagan, 1986.

laboring away inside you, and so far we understand what no more than about 2 percent ofthem do. (others put the figure at more like 50 percent; it depends, apparently, on what youmean by “understand.”)surprises at the cellular level turn up all the time. in nature, nitric oxide is a formidabletoxin and a common component of air pollution. so scientists were naturally a little surprisedwhen, in the mid-1980s, they found it being produced in a curiously devoted manner inhuman cells. its purpose was at first a mystery, but then scientists began to find it all over theplace—controlling the flow of blood and the energy levels of cells, attacking cancers andother pathogens, regulating the sense of smell, even assisting in penile erections. it alsoexplained why nitroglycerine, the well-known explosive, soothes the heart pain known asangina. (it is converted into nitric oxide in the bloodstream, relaxing the muscle linings ofvessels, allowing blood to flow more freely.) in barely the space of a decade this one gassysubstance went from extraneous toxin to ubiquitous elixir.

you  possess  “some  few  hundred”  different  types of cell, according to the belgianbiochemist christian de duve, and they vary enormously in size and shape, from nerve cellswhose filaments can stretch to several feet to tiny, disc-shaped red blood cells to the rod-shaped photocells that help to give us vision. they also come in a sumptuously wide range ofsizes—nowhere more strikingly than at the moment of conception, when a single beatingsperm confronts an egg eighty-five thousand times bigger than it (which rather puts the notionof male conquest into perspective). on average, however, a human cell is about twentymicrons wide—that is about two hundredths of a millimeter—which is too small to be seenbut roomy enough to hold thousands of complicated structures like mitochondria, and millionsupon millions of molecules. in the most literal way, cells also vary in liveliness. your skincells are all dead. it’s a somewhat galling notion to reflect that every inch of your surface isdeceased. if you are an average-sized adult you are lugging around about five pounds of deadskin, of which several billion tiny fragments are sloughed off each day. run a finger along adusty shelf and you are drawing a pattern very largely in old skin.

most living cells seldom last more than a month or so, but there are some notableexceptions. liver cells can survive for years, though the components within them may berenewed every few days. brain cells last as long as you do. you are issued a hundred billionor so at birth, and that is all you are ever going to get. it has been estimated that you lose fivehundred of them an hour, so if you have any serious thinking to do there really isn’t a momentto waste. the good news is that the individual components of your brain cells are constantlyrenewed so that, as with the liver cells, no part of them is actually likely to be more than abouta month old. indeed, it has been suggested that there isn’t a single bit of any of us—not somuch as a stray molecule—that was part of us nine years ago. it may not feel like it, but at thecellular level we are all youngsters.

the first person to describe a cell was robert hooke, whom we last encounteredsquabbling with isaac newton over credit for the invention of the inverse square law. hookeachieved many things in his sixty-eight years—he was both an accomplished theoretician anda dab hand at making ingenious and useful instruments—but nothing he did brought himgreater admiration than his popular book microphagia: or some physiological descriptions ofminiature bodies made by magnifying glasses, produced in 1665. it revealed to an enchantedpublic a universe of the very small that was far more diverse, crowded, and finely structuredthan anyone had ever come close to imagining.

among the microscopic features first identified by hooke were little chambers in plantsthat he called “cells” because they reminded him of monks’ cells. hooke calculated that aone-inch square of cork would contain 1,259,712,000 of these tiny chambers—the firstappearance of such a very large number anywhere in science. microscopes by this time hadbeen around for a generation or so, but what set hooke’s apart were their technicalsupremacy. they achieved magnifications of thirty times, making them the last word inseventeenth-century optical technology.

so it came as something of a shock when just a decade later hooke and the other membersof london’s royal society began to receive drawings and reports from an unlettered linendraper in holland employing magnifications of up to 275 times. the draper’s name wasantoni van leeuwenhoek. though he had little formal education and no background inscience, he was a perceptive and dedicated observer and a technical genius.

to this day it is not known how he got such magnificent magnifications from simplehandheld devices, which were little more than modest wooden dowels with a tiny bubble ofglass embedded in them, far more like magnifying glasses than what most of us think of asmicroscopes, but really not much like either. leeuwenhoek made a new instrument for everyexperiment he performed and was extremely secretive about his techniques, though he didsometimes offer tips to the british on how they might improve their resolutions.

2over a period of fifty years—beginning, remarkably enough, when he was already pastforty—he made almost two hundred reports to the royal society, all written in low dutch,the only tongue of which he was master. leeuwenhoek offered no interpretations, but simplythe facts of what he had found, accompanied by exquisite drawings. he sent reports on almosteverything that could be usefully examined—bread mold, a bee’s stinger, blood cells, teeth,hair, his own saliva, excrement, and semen (these last with fretful apologies for their unsavorynature)—nearly all of which had never been seen microscopically before.

after he reported finding “animalcules” in a sample of pepper water in 1676, the membersof the royal society spent a year with the best devices english technology could producesearching for the “little animals” before finally getting the magnification right. whatleeuwenhoek had found were protozoa. he calculated that there were 8,280,000 of these tinybeings in a single drop of water—more than the number of people in holland. the worldteemed with life in ways and numbers that no one had previously suspected.

inspired by leeuwenhoek’s fantastic findings, others began to peer into microscopes withsuch keenness that they sometimes found things that weren’t in fact there. one respecteddutch observer, nicolaus hartsoecker, was convinced he saw “tiny preformed men” in spermcells. he called the little beings “homunculi” and for some time many people believed that allhumans—indeed, all creatures—were simply vastly inflated versions of tiny but completeprecursor beings. leeuwenhoek himself occasionally got carried away with his enthusiasms.

in one of his least successful experiments he tried to study the explosive properties ofgunpowder by observing a small blast at close range; he nearly blinded himself in the process.

2leeuwenhoek was close friends with another delft notable, the artist jan vermeer. in the mid-1660s, vermeer,who previously had been a competent but not outstanding artist, suddenly developed the mastery of light andperspective for which he has been celebrated ever since. though it has never been proved, it has long beensuspected that he used a camera obscura, a device for projecting images onto a flat surface through a lens. nosuch device was listed among vermeers personal effects after his death, but it happens that the executor ofvermeers estate was none other than antoni van leeuwenhoek, the most secretive lens-maker of his day.

in 1683 leeuwenhoek discovered bacteria, but that was about as far as progress could getfor the next century and a half because of the limitations of microscope technology. not until1831 would anyone first see the nucleus of a cell—it was found by the scottish botanistrobert brown, that frequent but always shadowy visitor to the history of science. brown, wholived from 1773 to 1858, called it nucleus from the latin nucula, meaning little nut or kernel.

not until 1839, however, did anyone realize that all living matter is cellular. it was theodorschwann, a german, who had this insight, and it was not only comparatively late, as scientificinsights go, but not widely embraced at first. it wasn’t until the 1860s, and some landmarkwork by louis pasteur in france, that it was shown conclusively that life cannot arisespontaneously but must come from preexisting cells. the belief became known as the “celltheory,” and it is the basis of all modern biology.

the cell has been compared to many things, from “a complex chemical refinery” (by thephysicist james trefil) to “a vast, teeming metropolis” (the biochemist guy brown). a cell isboth of those things and neither. it is like a refinery in that it is devoted to chemical activityon a grand scale, and like a metropolis in that it is crowded and busy and filled withinteractions that seem confused and random but clearly have some system to them. but it is amuch more nightmarish place than any city or factory that you have ever seen. to begin withthere is no up or down inside the cell (gravity doesn’t meaningfully apply at the cellularscale), and not an atom’s width of space is unused. there is activity every where and aceaseless thrum of electrical energy. you may not feel terribly electrical, but you are. thefood we eat and the oxygen we breathe are combined in the cells into electricity. the reasonwe don’t give each other massive shocks or scorch the sofa when we sit is that it is allhappening on a tiny scale: a mere 0.1 volts traveling distances measured in nanometers.

however, scale that up and it would translate as a jolt of twenty million volts per meter, aboutthe same as the charge carried by the main body of a thunderstorm.

whatever their size or shape, nearly all your cells are built to fundamentally the same plan:

they have an outer casing or membrane, a nucleus wherein resides the necessary geneticinformation to keep you going, and a busy space between the two called the cytoplasm. themembrane is not, as most of us imagine it, a durable, rubbery casing, something that youwould need a sharp pin to prick. rather, it is made up of a type of fatty material known as alipid, which has the approximate consistency “of a light grade of machine oil,” to quotesherwin b. nuland. if that seems surprisingly insubstantial, bear in mind that at themicroscopic level things behave differently. to anything on a molecular scale water becomesa kind of heavy-duty gel, and a lipid is like iron.

if you could visit a cell, you wouldn’t like it. blown up to a scale at which atoms wereabout the size of peas, a cell itself would be a sphere roughly half a mile across, and supportedby a complex framework of girders called the cytoskeleton. within it, millions upon millionsof objects—some the size of basketballs, others the size of cars—would whiz about likebullets. there wouldn’t be a place you could stand without being pummeled and rippedthousands of times every second from every direction. even for its full-time occupants theinside of a cell is a hazardous place. each strand of dna is on average attacked or damagedonce every 8.4 seconds—ten thousand times in a day—by chemicals and other agents thatwhack into or carelessly slice through it, and each of these wounds must be swiftly stitched upif the cell is not to perish.

the proteins are especially lively, spinning, pulsating, and flying into each other up to abillion times a second. enzymes, themselves a type of protein, dash everywhere, performingup to a thousand tasks a second. like greatly speeded up worker ants, they busily build and
rebuild molecules, hauling a piece off this one, adding a piece to that one. some monitorpassing proteins and mark with a chemical those that are irreparably damaged or flawed. onceso selected, the doomed proteins proceed to a structure called a proteasome, where they arestripped down and their components used to build new proteins. some types of protein existfor less than half an hour; others survive for weeks. but all lead existences that areinconceivably frenzied. as de duve notes, “the molecular world must necessarily remainentirely beyond the powers of our imagination owing to the incredible speed with whichthings happen in it.”

but slow things down, to a speed at which the interactions can be observed, and thingsdon’t seem quite so unnerving. you can see that a cell is just millions of objects—lysosomes,endosomes, ribosomes, ligands, peroxisomes, proteins of every size and shape—bumping intomillions of other objects and performing mundane tasks: extracting energy from nutrients,assembling structures, getting rid of waste, warding off intruders, sending and receivingmessages, making repairs. typically a cell will contain some 20,000 different types of protein,and of these about 2,000 types will each be represented by at least 50,000 molecules. “thismeans,” says nuland, “that even if we count only those molecules present in amounts of morethan 50,000 each, the total is still a very minimum of 100 million protein molecules in eachcell. such a staggering figure gives some idea of the swarming immensity of biochemicalactivity within us.”

it is all an immensely demanding process. your heart must pump 75 gallons of blood anhour, 1,800 gallons every day, 657,000 gallons in a year—that’s enough to fill four olympic-sized swimming pools—to keep all those cells freshly oxygenated. (and that’s at rest. duringexercise the rate can increase as much as sixfold.) the oxygen is taken up by themitochondria. these are the cells’ power stations, and there are about a thousand of them in atypical cell, though the number varies considerably depending on what a cell does and howmuch energy it requires.

you may recall from an earlier chapter that the mitochondria are thought to have originatedas captive bacteria and that they now live essentially as lodgers in our cells, preserving theirown genetic instructions, dividing to their own timetable, speaking their own language. youmay also recall that we are at the mercy of their goodwill. here’s why. virtually all the foodand oxygen you take into your body are delivered, after processing, to the mitochondria,where they are converted into a molecule called adenosine triphosphate, or atp.

you may not have heard of atp, but it is what keeps you going. atp molecules areessentially little battery packs that move through the cell providing energy for all the cell’sprocesses, and you get through a lot of it. at any given moment, a typical cell in your bodywill have about one billion atp molecules in it, and in two minutes every one of them willhave been drained dry and another billion will have taken their place. every day you produceand use up a volume of atp equivalent to about half your body weight. feel the warmth ofyour skin. that’s your atp at work.

when cells are no longer needed, they die with what can only be called great dignity. theytake down all the struts and buttresses that hold them together and quietly devour theircomponent parts. the process is known as apoptosis or programmed cell death. every daybillions of your cells die for your benefit and billions of others clean up the mess. cells canalso die violently—for instance, when infected—but mostly they die because they are told to.

indeed, if not told to live—if not given some kind of active instruction from another cell—cells automatically kill themselves. cells need a lot of reassurance.

when, as occasionally happens, a cell fails to expire in the prescribed manner, but ratherbegins to divide and proliferate wildly, we call the result cancer. cancer cells are really justconfused cells. cells make this mistake fairly regularly, but the body has elaboratemechanisms for dealing with it. it is only very rarely that the process spirals out of control. onaverage, humans suffer one fatal malignancy for each 100 million billion cell divisions.

cancer is bad luck in every possible sense of the term.

the wonder of cells is not that things occasionally go wrong, but that they manageeverything so smoothly for decades at a stretch. they do so by constantly sending andmonitoring streams of messages—a cacophony of messages—from all around the body:

instructions, queries, corrections, requests for assistance, updates, notices to divide or expire.

most of these signals arrive by means of couriers called hormones, chemical entities such asinsulin, adrenaline, estrogen, and testosterone that convey information from remote outpostslike the thyroid and endocrine glands. still other messages arrive by telegraph from the brainor from regional centers in a process called paracrine signaling. finally, cells communicatedirectly with their neighbors to make sure their actions are coordinated.

what is perhaps most remarkable is that it is all just random frantic action, a sequence ofendless encounters directed by nothing more than elemental rules of attraction and repulsion.

there is clearly no thinking presence behind any of the actions of the cells. it all just happens,smoothly and repeatedly and so reliably that seldom are we even conscious of it, yet somehowall this produces not just order within the cell but a perfect harmony right across the organism.

in ways that we have barely begun to understand, trillions upon trillions of reflexive chemicalreactions add up to a mobile, thinking, decision-making you—or, come to that, a rather lessreflective but still incredibly organized dung beetle. every living thing, never forget, is awonder of atomic engineering.

indeed, some organisms that we think of as primitive enjoy a level of cellular organizationthat makes our own look carelessly pedestrian. disassemble the cells of a sponge (by passingthem through a sieve, for instance), then dump them into a solution, and they will find theirway back together and build themselves into a sponge again. you can do this to them overand over, and they will doggedly reassemble because, like you and me and every other livingthing, they have one overwhelming impulse: to continue to be.

and that’s because of a curious, determined, barely understood molecule that is itself notalive and for the most part doesn’t do anything at all. we call it dna, and to begin tounderstand its supreme importance to science and to us we need to go back 160 years or so tovictorian england and to the moment when the naturalist charles darwin had what has beencalled “the single best idea that anyone has ever had”—and then, for reasons that take a littleexplaining, locked it away in a drawer for the next fifteen years.

25    DARWIN’S SINGULAR NOTION

in the late summer or early autumn of 1859, whitwell elwin, editor of the respectedbritish journal the quarterly review, was sent an advance copy of a new book by thenaturalist charles darwin. elwin read the book with interest and agreed that it had merit, butfeared that the subject matter was too narrow to attract a wide audience. he urged darwin towrite a book about pigeons instead. “everyone is interested in pigeons,” he observedhelpfully.

elwin’s sage advice was ignored, and on the origin of species by means of naturalselection, or the preservation of favoured races in the struggle for life was published in latenovember 1859, priced at fifteen shillings. the first edition of 1,250 copies sold out on thefirst day. it has never been out of print, and scarcely out of controversy, in all the time since—not bad going for a man whose principal other interest was earthworms and who, but for asingle impetuous decision to sail around the world, would very probably have passed his lifeas an anonymous country parson known for, well, for an interest in earthworms.

charles robert darwin was born on february 12, 1809,1in shrewsbury, a sedate markettown in the west midlands of england. his father was a prosperous and well-regardedphysician. his mother, who died when charles was only eight, was the daughter of josiahwedgwood, of pottery fame.

darwin enjoyed every advantage of upbringing, but continually pained his widowed fatherwith his lackluster academic performance. “you care for nothing but shooting, dogs, and rat-catching, and you will be a disgrace to yourself and all your family,” his father wrote in a linethat nearly always appears just about here in any review of darwin’s early life. although hisinclination was to natural history, for his father’s sake he tried to study medicine at edinburghuniversity but couldn’t bear the blood and suffering. the experience of witnessing anoperation on an understandably distressed child—this was in the days before anesthetics, ofcourse—left him permanently traumatized. he tried law instead, but found that insupportablydull and finally managed, more or less by default, to acquire a degree in divinity fromcambridge.

a life in a rural vicarage seemed to await him when from out of the blue there came a moretempting offer. darwin was invited to sail on the naval survey ship hms beagle, essentiallyas dinner company for the captain, robert fitzroy, whose rank precluded his socializing withanyone other than a gentleman. fitzroy, who was very odd, chose darwin in part because heliked the shape of darwin’s nose. (it betokened depth of character, he believed.) darwin wasnot fitzroy’s first choice, but got the nod when fitzroy’s preferred companion dropped out.

from a twenty-first-century perspective the two men’s most striking joint feature was their1an auspicious date in history: on the same day in kentucky, abraham lincoln was born.

extreme youthfulness. at the time of sailing, fitzroy was only twenty-three, darwin justtwenty-two.

fitzroy’s formal assignment was to chart coastal waters, but his hobby—passion really—was to seek out evidence for a literal, biblical interpretation of creation. that darwin wastrained for the ministry was central to fitzroy’s decision to have him aboard. that darwinsubsequently proved to be not only liberal of view but less than wholeheartedly devoted tochristian fundamentals became a source of lasting friction between them.

darwin’s time aboard hms beagle, from 1831 to 1836, was obviously the formativeexperience of his life, but also one of the most trying. he and his captain shared a small cabin,which can’t have been easy as fitzroy was subject to fits of fury followed by spells ofsimmering resentment. he and darwin constantly engaged in quarrels, some “bordering oninsanity,” as darwin later recalled. ocean voyages tended to become melancholyundertakings at the best of times—the previous captain of the beagle had put a bullet throughhis brain during a moment of lonely gloom—and fitzroy came from a family well known fora depressive instinct. his uncle, viscount castlereagh, had slit his throat the previous decadewhile serving as chancellor of the exchequer. (fitzroy would himself commit suicide by thesame method in 1865.) even in his calmer moods, fitzroy proved strangely unknowable.

darwin was astounded to learn upon the conclusion of their voyage that almost at oncefitzroy married a young woman to whom he had long been betrothed. in five years indarwin’s company, he had not once hinted at an attachment or even mentioned her name.

in every other respect, however, the beagle voyage was a triumph. darwin experiencedadventure enough to last a lifetime and accumulated a hoard of specimens sufficient to makehis reputation and keep him occupied for years. he found a magnificent trove of giant ancientfossils, including the finest megatherium known to date; survived a lethal earthquake inchile; discovered a new species of dolphin (which he dutifully named delphinus fitzroyi);conducted diligent and useful geological investigations throughout the andes; and developeda new and much-admired theory for the formation of coral atolls, which suggested, notcoincidentally, that atolls could not form in less than a million years—the first hint of hislong-standing attachment to the extreme antiquity of earthly processes. in 1836, aged twenty-seven, he returned home after being away for five years and two days. he never left englandagain.

one thing darwin didn’t do on the voyage was propound the theory (or even a theory) ofevolution. for a start, evolution as a concept was already decades old by the 1830s. darwin’sown grandfather, erasmus, had paid tribute to evolutionary principles in a poem of inspiredmediocrity called “the temple of nature” years before charles was even born. it wasn’t untilthe younger darwin was back in england and read thomas malthus’s essay on the principleof population (which proposed that increases in food supply could never keep up withpopulation growth for mathematical reasons) that the idea began to percolate through his mindthat life is a perpetual struggle and that natural selection was the means by which somespecies prospered while others failed. specifically what darwin saw was that all organismscompeted for resources, and those that had some innate advantage would prosper and pass onthat advantage to their offspring. by such means would species continuously improve.

it seems an awfully simple idea—it is an awfully simple idea—but it explained a great deal,and darwin was prepared to devote his life to it. “how stupid of me not to have thought ofit!” t. h. huxley cried upon reading on the origin of species. it is a view that has beenechoed ever since.

interestingly, darwin didn’t use the phrase “survival of the fittest” in any of his work(though he did express his admiration for it). the expression was coined five years after thepublication of on the origin of species by herbert spencer in principles of biology in 1864.

nor did he employ the word evolution in print until the sixth edition of origin (by which timeits use had become too widespread to resist), preferring instead “descent with modification.”

nor, above all, were his conclusions in any way inspired by his noticing, during his time inthe galápagos islands, an interesting diversity in the beaks of finches. the story asconventionally told (or at least as frequently remembered by many of us) is that darwin,while traveling from island to island, noticed that the finches’ beaks on each island weremarvelously adapted for exploiting local resources—that on one island beaks were sturdy andshort and good for cracking nuts, while on the next island beaks were perhaps long and thinand well suited for winkling food out of crevices—and it was this that set him to thinking thatperhaps the birds had not been created this way, but had in a sense created themselves.

in fact, the birds had created themselves, but it wasn’t darwin who noticed it. at the timeof the beagle voyage, darwin was fresh out of college and not yet an accomplished naturalistand so failed to see that the galápagos birds were all of a type. it was his friend theornithologist john gould who realized that what darwin had found was lots of finches withdifferent talents. unfortunately, in his inexperience darwin had not noted which birds camefrom which islands. (he had made a similar error with tortoises.) it took years to sort themuddles out.

because of these oversights, and the need to sort through crates and crates of other beaglespecimens, it wasn’t until 1842, six years after his return to england, that darwin finallybegan to sketch out the rudiments of his new theory. these he expanded into a 230-page“sketch” two years later. and then he did an extraordinary thing: he put his notes away andfor the next decade and a half busied himself with other matters. he fathered ten children,devoted nearly eight years to writing an exhaustive opus on barnacles (“i hate a barnacle as noman ever did before,” he sighed, understandably, upon the work’s conclusion), and fell preyto strange disorders that left him chronically listless, faint, and “flurried,” as he put it. thesymptoms nearly always included a terrible nausea and generally also incorporatedpalpitations, migraines, exhaustion, trembling, spots before the eyes, shortness of breath,“swimming of the head,” and, not surprisingly, depression.

the cause of the illness has never been established, but the most romantic and perhapslikely of the many suggested possibilities is that he suffered from chagas’s disease, alingering tropical malady that he could have acquired from the bite of a benchuga bug insouth america. a more prosaic explanation is that his condition was psychosomatic. in eithercase, the misery was not. often he could work for no more than twenty minutes at a stretch,sometimes not that.

much of the rest of his time was devoted to a series of increasingly desperate treatments—icy plunge baths, dousings in vinegar, draping himself with “electric chains” that subjectedhim to small jolts of current. he became something of a hermit, seldom leaving his home inkent, down house. one of his first acts upon moving to the house was to erect a mirroroutside his study window so that he could identify, and if necessary avoid, callers.

darwin kept his theory to himself because he well knew the storm it would cause. in 1844,the year he locked his notes away, a book called vestiges of the natural history of creationroused much of the thinking world to fury by suggesting that humans might have evolvedfrom lesser primates without the assistance of a divine creator. anticipating the outcry, the
author had taken careful steps to conceal his identity, which he kept a secret from even hisclosest friends for the next forty years. some wondered if darwin himself might be the author.

others suspected prince albert. in fact, the author was a successful and generally unassumingscottish publisher named robert chambers whose reluctance to reveal himself had a practicaldimension as well as a personal one: his firm was a leading publisher of bibles. vestiges waswarmly blasted from pulpits throughout britain and far beyond, but also attracted a good dealof more scholarly ire. the edinburgh review devoted nearly an entire issue—eighty-fivepages—to pulling it to pieces. even t. h. huxley, a believer in evolution, attacked the bookwith some venom, unaware that the author was a friend.

2darwin’s manuscript might have remained locked away till his death but for an alarmingblow that arrived from the far east in the early summer of 1858 in the form of a packetcontaining a friendly letter from a young naturalist named alfred russel wallace and the draftof a paper, on the tendency of varieties to depart indefinitely from the original type,outlining a theory of natural selection that was uncannily similar to darwin’s secret jottings.

even some of the phrasing echoed darwin’s own. “i never saw a more striking coincidence,”

darwin reflected in dismay. “if wallace had my manuscript sketch written out in 1842, hecould not have made a better short abstract.”

wallace didn’t drop into darwin’s life quite as unexpectedly as is sometimes suggested.

the two were already corresponding, and wallace had more than once generously sentdarwin specimens that he thought might be of interest. in the process of these exchangesdarwin had discreetly warned wallace that he regarded the subject of species creation as hisown territory. “this summer will make the 20th year (!) since i opened my first note-book, onthe question of how & in what way do species & varieties differ from each other,” he hadwritten to wallace some time earlier. “i am now preparing my work for publication,” headded, even though he wasn’t really.

in any case, wallace failed to grasp what darwin was trying to tell him, and of course hecould have no idea that his own theory was so nearly identical to one that darwin had beenevolving, as it were, for two decades.

darwin was placed in an agonizing quandary. if he rushed into print to preserve his priority,he would be taking advantage of an innocent tip-off from a distant admirer. but if he steppedaside, as gentlemanly conduct arguably required, he would lose credit for a theory that he hadindependently propounded. wallace’s theory was, by wallace’s own admission, the result of aflash of insight; darwin’s was the product of years of careful, plodding, methodical thought. itwas all crushingly unfair.

to compound his misery, darwin’s youngest son, also named charles, had contracted scarletfever and was critically ill. at the height of the crisis, on june 28, the child died. despite thedistraction of his son’s illness, darwin found time to dash off letters to his friends charleslyell and joseph hooker, offering to step aside but noting that to do so would mean that allhis work, “whatever it may amount to, will be smashed.” lyell and hooker came up with thecompromise solution of presenting a summary of darwin’s and wallace’s ideas together. thevenue they settled on was a meeting of the linnaean society, which at the time was strugglingto find its way back into fashion as a seat of scientific eminence. on july 1, 1858, darwin’s2darwin was one of the few to guess correctly. he happened to be visiting chambers one day when an advancecopy of the sixth edition of vestiges was delivered. the keenness with which chambers checked the revisionswas something of a giveaway, though it appears the two men did not discuss it.

and wallace’s theory was unveiled to the world. darwin himself was not present. on the dayof the meeting, he and his wife were burying their son.

the darwin–wallace presentation was one of seven that evening—one of the others was onthe flora of angola—and if the thirty or so people in the audience had any idea that they werewitnessing the scientific highlight of the century, they showed no sign of it. no discussionfollowed. nor did the event attract much notice elsewhere. darwin cheerfully later noted thatonly one person, a professor haughton of dublin, mentioned the two papers in print and hisconclusion was “that all that was new in them was false, and what was true was old.”

wallace, still in the distant east, learned of these maneuverings long after the event, butwas remarkably equable and seemed pleased to have been included at all. he even referred tothe theory forever after as “darwinism.” much less amenable to darwin’s claim of prioritywas a scottish gardener named patrick matthew who had, rather remarkably, also come upwith the principles of natural selection—in fact, in the very year that darwin had set sail inthebeagle. unfortunately, matthew had published these views in a book called naval timberand arboriculture, which had been missed not just by darwin, but by the entire world.

matthew kicked up in a lively manner, with a letter to gardener’s chronicle, when he sawdarwin gaining credit everywhere for an idea that really was his. darwin apologized withouthesitation, though he did note for the record: “i think that no one will feel surprised thatneither i, nor apparently any other naturalist, has heard of mr. matthew’s views, consideringhow briefly they are given, and they appeared in the appendix to a work on naval timberand arboriculture.”

wallace continued for another fifty years as a naturalist and thinker, occasionally a verygood one, but increasingly fell from scientific favor by taking up dubious interests such asspiritualism and the possibility of life existing elsewhere in the universe. so the theorybecame, essentially by default, darwin’s alone.

darwin never ceased being tormented by his ideas. he referred to himself as “the devil’schaplain” and said that revealing the theory felt “like confessing a murder.” apart from allelse, he knew it deeply pained his beloved and pious wife. even so, he set to work at onceexpanding his manuscript into a book-length work. provisionally he called it an abstract ofan essay on the origin of species and varieties through natural selection —a title so tepidand tentative that his publisher, john murray, decided to issue just five hundred copies. butonce presented with the manuscript, and a slightly more arresting title, murray reconsideredand increased the initial print run to 1,250.

on the origin of species was an immediate commercial success, but rather less of a criticalone. darwin’s theory presented two intractable difficulties. it needed far more time than lordkelvin was willing to concede, and it was scarcely supported by fossil evidence. where,asked darwin’s more thoughtful critics, were the transitional forms that his theory so clearlycalled for? if new species were continuously evolving, then there ought to be lots ofintermediate forms scattered across the fossil record, but there were not.

3in fact, the record asit existed then (and for a long time afterward) showed no life at all right up to the moment ofthe famous cambrian explosion.

3by coincidence, in 1861, at the height of the controversy, just such evidence turned up when workers inbavaria found the bones of an ancient archaeopteryx, a creature halfway between a bird and a dinosaur. (it hadfeathers, but it also had teeth.) it was an impressive and helpful find, and its significance much debated, but asingle discovery could hardly be considered conclusive.

but now here was darwin, without any evidence, insisting that the earlier seas must havehad abundant life and that we just hadn’t found it yet because, for whatever reason, it hadn’tbeen preserved. it simply could not be otherwise, darwin maintained. “the case at presentmust remain inexplicable; and may be truly urged as a valid argument against the views hereentertained,” he allowed most candidly, but he refused to entertain an alternative possibility.

by way of explanation he speculated—inventively but incorrectly—that perhaps theprecambrian seas had been too clear to lay down sediments and thus had preserved no fossils.

even darwin’s closest friends were troubled by the blitheness of some of his assertions.

adam sedgwick, who had taught darwin at cambridge and taken him on a geological tour ofwales in 1831, said the book gave him “more pain than pleasure.” louis agassiz dismissed itas poor conjecture. even lyell concluded gloomily: “darwin goes too far.”

1. h. huxley disliked darwin’s insistence on huge amounts of geological time because hewas a saltationist, which is to say a believer in the idea that evolutionary changes happen notgradually but suddenly. saltationists (the word comes from the latin for “leap”) couldn’taccept that complicated organs could ever emerge in slow stages. what good, after all, is one-tenth of a wing or half an eye? such organs, they thought, only made sense if they appeared ina finished state.

the belief was surprising in as radical a spirit as huxley because it closely recalled a veryconservative religious notion first put forward by the english theologian william paley in1802 and known as argument from design. paley contended that if you found a pocket watchon the ground, even if you had never seen such a thing before, you would instantly perceivethat it had been made by an intelligent entity. so it was, he believed, with nature: itscomplexity was proof of its design. the notion was a powerful one in the nineteenth century,and it gave darwin trouble too. “the eye to this day gives me a cold shudder,” heacknowledged in a letter to a friend. in the origin he conceded that it “seems, i freely confess,absurd in the highest possible degree” that natural selection could produce such an instrumentin gradual steps.

even so, and to the unending exasperation of his supporters, darwin not only insisted thatall change was gradual, but in nearly every edition of origin he stepped up the amount of timehe supposed necessary to allow evolution to progress, which pushed his ideas increasingly outof favor. “eventually,” according to the scientist and historian jeffrey schwartz, “darwin lostvirtually all the support that still remained among the ranks of fellow natural historians andgeologists.”

ironically, considering that darwin called his book on the origin of species, the one thinghe couldn’t explain was how species originated. darwin’s theory suggested a mechanism forhow a species might become stronger or better or faster—in a word, fitter—but gave noindication of how it might throw up a new species. a scottish engineer, fleeming jenkin,considered the problem and noted an important flaw in darwin’s argument. darwin believedthat any beneficial trait that arose in one generation would be passed on to subsequentgenerations, thus strengthening the species.

jenkin pointed out that a favorable trait in one parent wouldn’t become dominant insucceeding generations, but in fact would be diluted through blending. if you pour whiskeyinto a tumbler of water, you don’t make the whiskey stronger, you make it weaker. and if youpour that dilute solution into another glass of water, it becomes weaker still. in the same way,any favorable trait introduced by one parent would be successively watered down by
subsequent matings until it ceased to be apparent at all. thus darwin’s theory was not a recipefor change, but for constancy. lucky flukes might arise from time to time, but they wouldsoon vanish under the general impulse to bring everything back to a stable mediocrity. ifnatural selection were to work, some alternative, unconsidered mechanism was required.

unknown to darwin and everyone else, eight hundred miles away in a tranquil corner ofmiddle europe a retiring monk named gregor mendel was coming up with the solution.

mendel was born in 1822 to a humble farming family in a backwater of the austrianempire in what is now the czech republic. schoolbooks once portrayed him as a simple butobservant provincial monk whose discoveries were largely serendipitous—the result ofnoticing some interesting traits of inheritance while pottering about with pea plants in themonastery’s kitchen garden. in fact, mendel was a trained scientist—he had studied physicsand mathematics at the olmütz philosophical institute and the university of vienna—and hebrought scientific discipline to all he did. moreover, the monastery at brno where he livedfrom 1843 was known as a learned institution. it had a library of twenty thousand books and atradition of careful scientific investigation.

before embarking on his experiments, mendel spent two years preparing his controlspecimens, seven varieties of pea, to make sure they bred true. then, helped by two full-timeassistants, he repeatedly bred and crossbred hybrids from thirty thousand pea plants. it wasdelicate work, requiring them to take the most exacting pains to avoid accidental cross-fertilization and to note every slight variation in the growth and appearance of seeds, pods,leaves, stems, and flowers. mendel knew what he was doing.

he never used the word gene —it wasn’t coined until 1913, in an english medicaldictionary—though he did invent the terms dominant and recessive. what he established wasthat every seed contained two “factors” or “elemente,” as he called them—a dominant oneand a recessive one—and these factors, when combined, produced predictable patterns ofinheritance.

the results he converted into precise mathematical formulae. altogether mendel spenteight years on the experiments, then confirmed his results with similar experiments onflowers, corn, and other plants. if anything, mendel was too scientific in his approach, forwhen he presented his findings at the february and march meetings of the natural historysociety of brno in 1865, the audience of about forty listened politely but was conspicuouslyunmoved, even though the breeding of plants was a matter of great practical interest to manyof the members.

when mendel’s report was published, he eagerly sent a copy to the great swiss botanistkarl-wilhelm von n?geli, whose support was more or less vital for the theory’s prospects.

unfortunately, n?geli failed to perceive the importance of what mendel had found. hesuggested that mendel try breeding hawkweed. mendel obediently did as n?geli suggested,but quickly realized that hawkweed had none of the requisite features for studying heritability.

it was evident to him that n?geli had not read the paper closely, or possibly at all. frustrated,mendel retired from investigating heritability and spent the rest of his life growingoutstanding vegetables and studying bees, mice, and sunspots, among much else. eventuallyhe was made abbot.

mendel’s findings weren’t quite as widely ignored as is sometimes suggested. his studyreceived a glowing entry in the encyclopaedia britannica —then a more leading record of
scientific thought than now—and was cited repeatedly in an important paper by the germanwilhelm olbers focke. indeed, it was because mendel’s ideas never entirely sank below thewaterline of scientific thought that they were so easily recovered when the world was readyfor them.

together, without realizing it, darwin and mendel laid the groundwork for all of lifesciences in the twentieth century. darwin saw that all living things are connected, thatultimately they “trace their ancestry to a single, common source,” while mendel’s workprovided the mechanism to explain how that could happen. the two men could easily havehelped each other. mendel owned a german edition of the origin of species, which he isknown to have read, so he must have realized the applicability of his work to darwin’s, yet heappears to have made no effort to get in touch. and darwin for his part is known to havestudied focke’s influential paper with its repeated references to mendel’s work, but didn’tconnect them to his own studies.

the one thing everyone thinks featured in darwin’s argument, that humans are descendedfrom apes, didn’t feature at all except as one passing allusion. even so, it took no great leap ofimagination to see the implications for human development in darwin’s theories, and itbecame an immediate talking point.

the showdown came on saturday, june 30, 1860, at a meeting of the british associationfor the advancement of science in oxford. huxley had been urged to attend by robertchambers, author of vestiges of the natural history of creation, though he was still unawareof chambers’s connection to that contentious tome. darwin, as ever, was absent. the meetingwas held at the oxford zoological museum. more than a thousand people crowded into thechamber; hundreds more were turned away. people knew that something big was going tohappen, though they had first to wait while a slumber-inducing speaker named john williamdraper of new york university bravely slogged his way through two hours of introductoryremarks on “the intellectual development of europe considered with reference to the viewsof mr. darwin.”

finally, the bishop of oxford, samuel wilberforce, rose to speak. wilberforce had beenbriefed (or so it is generally assumed) by the ardent anti-darwinian richard owen, who hadbeen a guest in his home the night before. as nearly always with events that end in uproar,accounts vary widely on what exactly transpired. in the most popular version, wilberforce,when properly in flow, turned to huxley with a dry smile and demanded of him whether heclaimed attachment to the apes by way of his grandmother or grandfather. the remark wasdoubtless intended as a quip, but it came across as an icy challenge. according to his ownaccount, huxley turned to his neighbor and whispered, “the lord hath delivered him into myhands,” then rose with a certain relish.

others, however, recalled a huxley trembling with fury and indignation. at all events,huxley declared that he would rather claim kinship to an ape than to someone who used hiseminence to propound uninformed twaddle in what was supposed to be a serious scientificforum. such a riposte was a scandalous impertinence, as well as an insult to wilberforce’soffice, and the proceedings instantly collapsed in tumult. a lady brewster fainted. robertfitzroy, darwin’s companion on the beagle twenty-five years before, wandered through thehall with a bible held aloft, shouting, “the book, the book.” (he was at the conference topresent a paper on storms in his capacity as head of the newly created meteorologicaldepartment.) interestingly, each side afterward claimed to have routed the other.

darwin did eventually make his belief in our kinship with the apes explicit in the descentof man in 1871. the conclusion was a bold one since nothing in the fossil record supportedsuch a notion. the only known early human remains of that time were the famous neandertalbones from germany and a few uncertain fragments of jawbones, and many respectedauthorities refused to believe even in their antiquity. the descent of man was altogether amore controversial book, but by the time of its appearance the world had grown less excitableand its arguments caused much less of a stir.

for the most part, however, darwin passed his twilight years with other projects, most ofwhich touched only tangentially on questions of natural selection. he spent amazingly longperiods picking through bird droppings, scrutinizing the contents in an attempt to understandhow seeds spread between continents, and spent years more studying the behavior of worms.

one of his experiments was to play the piano to them, not to amuse them but to study theeffects on them of sound and vibration. he was the first to realize how vitally importantworms are to soil fertility. “it may be doubted whether there are many other animals whichhave played so important a part in the history of the world,” he wrote in his masterwork on thesubject, the formation of vegetable mould through the action of worms (1881), which wasactually more popular thanon the origin of species had ever been. among his other bookswere on the various contrivances by which british and foreign orchids are fertilised byinsects (1862), expressions of the emotions in man and animals (1872), which sold almost5,300 copies on its first day, the effects of cross and self fertilization in the vegetablekingdom (1876)—a subject that came improbably close to mendel’s own work, withoutattaining anything like the same insights—and his last book, the power of movement inplants. finally, but not least, he devoted much effort to studying the consequences ofinbreeding—a matter of private interest to him. having married his own cousin, darwinglumly suspected that certain physical and mental frailties among his children arose from alack of diversity in his family tree.

darwin was often honored in his lifetime, but never for on the origin of species ordescentof man. when the royal society bestowed on him the prestigious copley medal it was for hisgeology, zoology, and botany, not evolutionary theories, and the linnaean society wassimilarly pleased to honor darwin without embracing his radical notions. he was neverknighted, though he was buried in westminster abbey—next to newton. he died at down inapril 1882. mendel died two years later.

darwin’s theory didn’t really gain widespread acceptance until the 1930s and 1940s, withthe advance of a refined theory called, with a certain hauteur, the modern synthesis,combining darwin’s ideas with those of mendel and others. for mendel, appreciation wasalso posthumous, though it came somewhat sooner. in 1900, three scientists workingseparately in europe rediscovered mendel’s work more or less simultaneously. it was onlybecause one of them, a dutchman named hugo de vries, seemed set to claim mendel’sinsights as his own that a rival made it noisily clear that the credit really lay with the forgottenmonk.

the world was almost ready, but not quite, to begin to understand how we got here—howwe made each other. it is fairly amazing to reflect that at the beginning of the twentiethcentury, and for some years beyond, the best scientific minds in the world couldn’t actuallytell you where babies came from.

and these, you may recall, were men who thought science was nearly at an end.

26    THE STUFF OF LIFE

if your two parents hadn’t bonded just when they did—possibly to the second, possiblyto the nanosecond—you wouldn’t be here. and if their parents hadn’t bonded in a preciselytimely manner, you wouldn’t be here either. and if their parents hadn’t done likewise, andtheir parents before them, and so on, obviously and indefinitely, you wouldn’t be here.

push backwards through time and these ancestral debts begin to add up. go back just eightgenerations to about the time that charles darwin and abraham lincoln were born, andalready there are over 250 people on whose timely couplings your existence depends.

continue further, to the time of shakespeare and the mayflower pilgrims, and you have nofewer than 16,384 ancestors earnestly exchanging genetic material in a way that would,eventually and miraculously, result in you.

at twenty generations ago, the number of people procreating on your behalf has risen to1,048,576. five generations before that, and there are no fewer than 33,554,432 men andwomen on whose devoted couplings your existence depends. by thirty generations ago, yourtotal number of forebears—remember, these aren’t cousins and aunts and other incidentalrelatives, but only parents and parents of parents in a line leading ineluctably to you—is overone billion (1,073,741,824, to be precise). if you go back sixty-four generations, to the time ofthe romans, the number of people on whose cooperative efforts your eventual existencedepends has risen to approximately 1,000,000,000,000,000,000, which is several thousandtimes the total number of people who have ever lived.

clearly something has gone wrong with our math here. the answer, it may interest you tolearn, is that your line is not pure. you couldn’t be here without a little incest—actually quitea lot of incest—albeit at a genetically discreet remove. with so many millions of ancestors inyour background, there will have been many occasions when a relative from your mother’sside of the family procreated with some distant cousin from your father’s side of the ledger. infact, if you are in a partnership now with someone from your own race and country, thechances are excellent that you are at some level related. indeed, if you look around you on abus or in a park or café or any crowded place, most of the people you see are very probablyrelatives. when someone boasts to you that he is descended from william the conqueror orthe mayflower pilgrims, you should answer at once: “me, too!” in the most literal andfundamental sense we are all family.

we are also uncannily alike. compare your genes with any other human being’s and onaverage they will be about 99.9 percent the same. that is what makes us a species. the tinydifferences in that remaining 0.1 percent—“roughly one nucleotide base in every thousand,”

to quote the british geneticist and recent nobel laureate john sulston—are what endow uswith our individuality. much has been made in recent years of the unraveling of the human
genome. in fact, there is no such thing as “the” human genome. every human genome isdifferent. otherwise we would all be identical. it is the endless recombinations of ourgenomes—each nearly identical, but not quite—that make us what we are, both as individualsand as a species.

but what exactly is this thing we call the genome? and what, come to that, are genes?

well, start with a cell again. inside the cell is a nucleus, and inside each nucleus are thechromosomes—forty-six little bundles of complexity, of which twenty-three come from yourmother and twenty-three from your father. with a very few exceptions, every cell in yourbody—99.999 percent of them, say—carries the same complement of chromosomes. (theexceptions are red blood cells, some immune system cells, and egg and sperm cells, which forvarious organizational reasons don’t carry the full genetic package.) chromosomes constitutethe complete set of instructions necessary to make and maintain you and are made of longstrands of the little wonder chemical called deoxyribonucleic acid or dna—“the mostextraordinary molecule on earth,” as it has been called.

dna exists for just one reason—to create more dna—and you have a lot of it inside you:

about six feet of it squeezed into almost every cell. each length of dna comprises some 3.2billion letters of coding, enough to provide 103,480,000,000possible combinations, “guaranteed tobe unique against all conceivable odds,” in the words of christian de duve. that’s a lot ofpossibility—a one followed by more than three billion zeroes. “it would take more than fivethousand average-size books just to print that figure,” notes de duve. look at yourself in themirror and reflect upon the fact that you are beholding ten thousand trillion cells, and thatalmost every one of them holds two yards of densely compacted dna, and you begin toappreciate just how much of this stuff you carry around with you. if all your dna werewoven into a single fine strand, there would be enough of it to stretch from the earth to themoon and back not once or twice but again and again. altogether, according to onecalculation, you may have as much as twenty million kilometers of dna bundled up insideyou.

your body, in short, loves to make dna and without it you couldn’t live. yet dna is notitself alive. no molecule is, but dna is, as it were, especially unalive. it is “among the mostnonreactive, chemically inert molecules in the living world,” in the words of the geneticistrichard lewontin. that is why it can be recovered from patches of long-dried blood or semenin murder investigations and coaxed from the bones of ancient neandertals. it also explainswhy it took scientists so long to work out how a substance so mystifyingly low key—so, in aword, lifeless—could be at the very heart of life itself.

as a known entity, dna has been around longer than you might think. it was discoveredas far back as 1869 by johann friedrich miescher, a swiss scientist working at the universityof tübingen in germany. while delving microscopically through the pus in surgicalbandages, miescher found a substance he didn’t recognize and called it nuclein (because itresided in the nuclei of cells). at the time, miescher did little more than note its existence, butnuclein clearly remained on his mind, for twenty-three years later in a letter to his uncle heraised the possibility that such molecules could be the agents behind heredity. this was anextraordinary insight, but one so far in advance of the day’s scientific requirements that itattracted no attention at all.

for most of the next half century the common assumption was that the material—nowcalled deoxyribonucleic acid, or dna—had at most a subsidiary role in matters of heredity. itwas too simple. it had just four basic components, called nucleotides, which was like having
an alphabet of just four letters. how could you possibly write the story of life with such arudimentary alphabet? (the answer is that you do it in much the way that you create complexmessages with the simple dots and dashes of morse code—by combining them.) dna didn’tdo anything at all, as far as anyone could tell. it just sat there in the nucleus, possibly bindingthe chromosome in some way or adding a splash of acidity on command or fulfilling someother trivial task that no one had yet thought of. the necessary complexity, it was thought,had to exist in proteins in the nucleus.

there were, however, two problems with dismissing dna. first, there was so much of it:

two yards in nearly every nucleus, so clearly the cells esteemed it in some important way. ontop of this, it kept turning up, like the suspect in a murder mystery, in experiments. in twostudies in particular, one involving the pneumonococcus bacterium and another involvingbacteriophages (viruses that infect bacteria), dna betrayed an importance that could only beexplained if its role were more central than prevailing thought allowed. the evidencesuggested that dna was somehow involved in the making of proteins, a process vital to life,yet it was also clear that proteins were being made outside the nucleus, well away from thedna that was supposedly directing their assembly.

no one could understand how dna could possibly be getting messages to the proteins. theanswer, we now know, was rna, or ribonucleic acid, which acts as an interpreter betweenthe two. it is a notable oddity of biology that dna and proteins don’t speak the samelanguage. for almost four billion years they have been the living world’s great double act, andyet they answer to mutually incompatible codes, as if one spoke spanish and the other hindi.

to communicate they need a mediator in the form of rna. working with a kind of chemicalclerk called a ribosome, rna translates information from a cell’s dna into terms proteinscan understand and act upon.

however, by the early 1900s, where we resume our story, we were still a very long wayfrom understanding that, or indeed almost anything else to do with the confused business ofheredity.

clearly there was a need for some inspired and clever experimentation, and happily the ageproduced a young person with the diligence and aptitude to undertake it. his name wasthomas hunt morgan, and in 1904, just four years after the timely rediscovery of mendel’sexperiments with pea plants and still almost a decade before gene would even become a word,he began to do remarkably dedicated things with chromosomes.

chromosomes had been discovered by chance in 1888 and were so called because theyreadily absorbed dye and thus were easy to see under the microscope. by the turn of thetwentieth century it was strongly suspected that they were involved in the passing on of traits,but no one knew how, or even really whether, they did this.

morgan chose as his subject of study a tiny, delicate fly formally called drosophilamelanogaster, but more commonly known as the fruit fly (or vinegar fly, banana fly, orgarbage fly). drosophila is familiar to most of us as that frail, colorless insect that seems tohave a compulsive urge to drown in our drinks. as laboratory specimens fruit flies had certainvery attractive advantages: they cost almost nothing to house and feed, could be bred by themillions in milk bottles, went from egg to productive parenthood in ten days or less, and hadjust four chromosomes, which kept things conveniently simple.

working out of a small lab (which became known inevitably as the fly room) inschermerhorn hall at columbia university in new york, morgan and his team embarked ona program of meticulous breeding and crossbreeding involving millions of flies (onebiographer says billions, though that is probably an exaggeration), each of which had to becaptured with tweezers and examined under a jeweler’s glass for any tiny variations ininheritance. for six years they tried to produce mutations by any means they could think of—zapping the flies with radiation and x-rays, rearing them in bright light and darkness, bakingthem gently in ovens, spinning them crazily in centrifuges—but nothing worked. morgan wason the brink of giving up when there occurred a sudden and repeatable mutation—a fly thathad white eyes rather than the usual red ones. with this breakthrough, morgan and hisassistants were able to generate useful deformities, allowing them to track a trait throughsuccessive generations. by such means they could work out the correlations betweenparticular characteristics and individual chromosomes, eventually proving to more or lesseveryone’s satisfaction that chromosomes were at the heart of inheritance.

the problem, however, remained the next level of biological intricacy: the enigmatic genesand the dna that composed them. these were much trickier to isolate and understand. aslate as 1933, when morgan was awarded a nobel prize for his work, many researchers stillweren’t convinced that genes even existed. as morgan noted at the time, there was noconsensus “as to what the genes are—whether they are real or purely fictitious.” it may seemsurprising that scientists could struggle to accept the physical reality of something sofundamental to cellular activity, but as wallace, king, and sanders point out in biology: thescience of life (that rarest thing: a readable college text), we are in much the same positiontoday with mental processes such as thought and memory. we know that we have them, ofcourse, but we don’t know what, if any, physical form they take. so it was for the longest timewith genes. the idea that you could pluck one from your body and take it away for study wasas absurd to many of morgan’s peers as the idea that scientists today might capture a straythought and examine it under a microscope.

what was certainly true was that something associated with chromosomes was directingcell replication. finally, in 1944, after fifteen years of effort, a team at the rockefellerinstitute in manhattan, led by a brilliant but diffident canadian named oswald avery,succeeded with an exceedingly tricky experiment in which an innocuous strain of bacteria wasmade permanently infectious by crossing it with alien dna, proving that dna was far morethan a passive molecule and almost certainly was the active agent in heredity. the austrian-born biochemist erwin chargaff later suggested quite seriously that avery’s discovery wasworth two nobel prizes.

unfortunately, avery was opposed by one of his own colleagues at the institute, a strong-willed and disagreeable protein enthusiast named alfred mirsky, who did everything in hispower to discredit avery’s work—including, it has been said, lobbying the authorities at thekarolinska institute in stockholm not to give avery a nobel prize. avery by this time wassixty-six years old and tired. unable to deal with the stress and controversy, he resigned hisposition and never went near a lab again. but other experiments elsewhere overwhelminglysupported his conclusions, and soon the race was on to find the structure of dna.

had you been a betting person in the early 1950s, your money would almost certainly havebeen on linus pauling of caltech, america’s leading chemist, to crack the structure of dna.

pauling was unrivaled in determining the architecture of molecules and had been a pioneer inthe field of x-ray crystallography, a technique that would prove crucial to peering into theheart of dna. in an exceedingly distinguished career, he would win two nobel prizes (for chemistry in 1954 and peace in 1962), but with dna he became convinced that the structurewas a triple helix, not a double one, and never quite got on the right track. instead, victory fellto an unlikely quartet of scientists in england who didn’t work as a team, often weren’t onspeaking terms, and were for the most part novices in the field.

of the four, the nearest to a conventional boffin was maurice wilkins, who had spent muchof the second world war helping to design the atomic bomb. two of the others, rosalindfranklin and francis crick, had passed their war years working on mines for the britishgovernment—crick of the type that blow up, franklin of the type that produce coal.

the most unconventional of the foursome was james watson, an american prodigy whohad distinguished himself as a boy as a member of a highly popular radio program called thequiz kids (and thus could claim to be at least part of the inspiration for some of the membersof the glass family in franny and zooey and other works by j. d. salinger) and who hadentered the university of chicago aged just fifteen. he had earned his ph.d. by the age oftwenty-two and was now attached to the famous cavendish laboratory in cambridge. in1951, he was a gawky twenty-three-year-old with a strikingly lively head of hair that appearsin photographs to be straining to attach itself to some powerful magnet just out of frame.

crick, twelve years older and still without a doctorate, was less memorably hirsute andslightly more tweedy. in watson’s account he is presented as blustery, nosy, cheerfullyargumentative, impatient with anyone slow to share a notion, and constantly in danger ofbeing asked to go elsewhere. neither was formally trained in biochemistry.

their assumption was that if you could determine the shape of a dna molecule you wouldbe able to see—correctly, as it turned out—how it did what it did. they hoped to achieve this,it would appear, by doing as little work as possible beyond thinking, and no more of that thanwas absolutely necessary. as watson cheerfully (if a touch disingenuously) remarked in hisautobiographical book the double helix, “it was my hope that the gene might be solvedwithout my learning any chemistry.” they weren’t actually assigned to work on dna, and atone point were ordered to stop it. watson was ostensibly mastering the art of crystallography;crick was supposed to be completing a thesis on the x-ray diffraction of large molecules.

although crick and watson enjoy nearly all the credit in popular accounts for solving themystery of dna, their breakthrough was crucially dependent on experimental work done bytheir competitors, the results of which were obtained “fortuitously,” in the tactful words of thehistorian lisa jardine. far ahead of them, at least at the beginning, were two academics atking’s college in london, wilkins and franklin.

the new zealand–born wilkins was a retiring figure, almost to the point of invisibility. a1998 pbs documentary on the discovery of the structure of dna—a feat for which he sharedthe 1962 nobel prize with crick and watson—managed to overlook him entirely.

the most enigmatic character of all was franklin. in a severely unflattering portrait,watson in the double helix depicted franklin as a woman who was unreasonable, secretive,chronically uncooperative, and—this seemed especially to irritate him—almost willfullyunsexy. he allowed that she “was not unattractive and might have been quite stunning had shetaken even a mild interest in clothes,” but in this she disappointed all expectations. she didn’t
even use lipstick, he noted in wonder, while her dress sense “showed all the imagination ofenglish blue-stocking adolescents.”

1however, she did have the best images in existence of the possible structure of dna,achieved by means of x-ray crystallography, the technique perfected by linus pauling.

crystallography had been used successfully to map atoms in crystals (hence“crystallography”), but dna molecules were a much more finicky proposition. only franklinwas managing to get good results from the process, but to wilkins’s perennial exasperationshe refused to share her findings.

if franklin was not warmly forthcoming with her findings, she cannot be altogetherblamed. female academics at king’s in the 1950s were treated with a formalized disdain thatdazzles modern sensibilities (actually any sensibilities). however senior or accomplished,they were not allowed into the college’s senior common room but instead had to take theirmeals in a more utilitarian chamber that even watson conceded was “dingily pokey.” on topof this she was being constantly pressed—at times actively harassed—to share her results witha trio of men whose desperation to get a peek at them was seldom matched by more engagingqualities, like respect. “i’m afraid we always used to adopt—let’s say a patronizing attitudetoward her,” crick later recalled. two of these men were from a competing institution and thethird was more or less openly siding with them. it should hardly come as a surprise that shekept her results locked away.

that wilkins and franklin did not get along was a fact that watson and crick seem to haveexploited to their benefit. although crick and watson were trespassing rather unashamedlyon wilkins’s territory, it was with them that he increasingly sided—not altogether surprisinglysince franklin herself was beginning to act in a decidedly queer way. although her resultsshowed that dna definitely was helical in shape, she insisted to all that it was not. towilkins’s presumed dismay and embarrassment, in the summer of 1952 she posted a mocknotice around the king’s physics department that said: “it is with great regret that we have toannounce the death, on friday 18th july 1952 of d.n.a. helix. . . . it is hoped that dr. m.h.f.

wilkins will speak in memory of the late helix.”

the outcome of all this was that in january 1953, wilkins showed watson franklin’simages, “apparently without her knowledge or consent.” it would be an understatement to callit a significant help. years later watson conceded that it “was the key event . . . it mobilizedus.” armed with the knowledge of the dna molecule’s basic shape and some importantelements of its dimensions, watson and crick redoubled their efforts. everything now seemedto go their way. at one point pauling was en route to a conference in england at which hewould in all likelihood have met with wilkins and learned enough to correct themisconceptions that had put him on the wrong line of inquiry, but this was the mccarthy eraand pauling found himself detained at idlewild airport in new york, his passport confiscated,on the grounds that he was too liberal of temperament to be allowed to travel abroad. crickand watson also had the no less convenient good fortune that pauling’s son was working atthe cavendish and innocently kept them abreast of any news of developments and setbacks athome.

still facing the possibility of being trumped at any moment, watson and crick appliedthemselves feverishly to the problem. it was known that dna had four chemical1in 1968, harvard university press canceled publication of the double helix after crick and wilkinscomplained about its characterizations, which the science historian lisa jardine has described as “gratuitouslyhurtful.” the descriptions quoted above are after watson softened his comments.

components—called adenine, guanine, cytosine, and thiamine—and that these paired up inparticular ways. by playing with pieces of cardboard cut into the shapes of molecules, watsonand crick were able to work out how the pieces fit together. from this they made a meccano-like model—perhaps the most famous in modern science—consisting of metal plates boltedtogether in a spiral, and invited wilkins, franklin, and the rest of the world to have a look.

any informed person could see at once that they had solved the problem. it was withoutquestion a brilliant piece of detective work, with or without the boost of franklin’s picture.

the april 25, 1953, edition of nature carried a 900-word article by watson and crick titled“a structure for deoxyribose nucleic acid.” accompanying it were separate articles bywilkins and franklin. it was an eventful time in the world—edmund hillary was just about toclamber to the top of everest while elizabeth ii was imminently to be crowned queen ofengland—so the discovery of the secret of life was mostly overlooked. it received a smallmention in the news chronicle and was ignored elsewhere.

rosalind franklin did not share in the nobel prize. she died of ovarian cancer at the age ofjust thirty-seven in 1958, four years before the award was granted. nobel prizes are notawarded posthumously. the cancer almost certainly arose as a result of chronic overexposureto x-rays through her work and needn’t have happened. in her much-praised 2002 biographyof franklin, brenda maddox noted that franklin rarely wore a lead apron and often steppedcarelessly in front of a beam. oswald avery never won a nobel prize either and was alsolargely overlooked by posterity, though he did at least have the satisfaction of living just longenough to see his findings vindicated. he died in 1955.

watson and crick’s discovery wasn’t actually confirmed until the 1980s. as crick said inone of his books: “it took over twenty-five years for our model of dna to go from being onlyrather plausible, to being very plausible . . . and from there to being virtually certainlycorrect.”

even so, with the structure of dna understood progress in genetics was swift, and by 1968the journal science could run an article titled “that was the molecular biology that was,”

suggesting—it hardly seems possible, but it is so—that the work of genetics was nearly at anend.

in fact, of course, it was only just beginning. even now there is a great deal about dna thatwe scarcely understand, not least why so much of it doesn’t actually seem to do anything.

ninety-seven percent of your dna consists of nothing but long stretches of meaninglessgarble—“junk,” or “non-coding dna,” as biochemists prefer to put it. only here and therealong each strand do you find sections that control and organize vital functions. these are thecurious and long-elusive genes.

genes are nothing more (nor less) than instructions to make proteins. this they do with acertain dull fidelity. in this sense, they are rather like the keys of a piano, each playing asingle note and nothing else, which is obviously a trifle monotonous. but combine the genes,as you would combine piano keys, and you can create chords and melodies of infinite variety.

put all these genes together, and you have (to continue the metaphor) the great symphony ofexistence known as the human genome.

an alternative and more common way to regard the genome is as a kind of instructionmanual for the body. viewed this way, the chromosomes can be imagined as the book’schapters and the genes as individual instructions for making proteins. the words in which the
instructions are written are called codons, and the letters are known as bases. the bases—theletters of the genetic alphabet—consist of the four nucleotides mentioned a page or two back:

adenine, thiamine, guanine, and cytosine. despite the importance of what they do, thesesubstances are not made of anything exotic. guanine, for instance, is the same stuff thatabounds in, and gives its name to, guano.

the shape of a dna molecule, as everyone knows, is rather like a spiral staircase ortwisted rope ladder: the famous double helix. the uprights of this structure are made of a typeof sugar called deoxyribose, and the whole of the helix is a nucleic acid—hence the name“deoxyribonucleic acid.” the rungs (or steps) are formed by two bases joining across thespace between, and they can combine in only two ways: guanine is always paired withcytosine and thiamine always with adenine. the order in which these letters appear as youmove up or down the ladder constitutes the dna code; logging it has been the job of thehuman genome project.

now the particular brilliance of dna lies in its manner of replication. when it is time toproduce a new dna molecule, the two strands part down the middle, like the zipper on ajacket, and each half goes off to form a new partnership. because each nucleotide along astrand pairs up with a specific other nucleotide, each strand serves as a template for thecreation of a new matching strand. if you possessed just one strand of your own dna, youcould easily enough reconstruct the matching side by working out the necessary partnerships:

if the topmost rung on one strand was made of guanine, then you would know that thetopmost rung on the matching strand must be cytosine. work your way down the ladderthrough all the nucleotide pairings, and eventually you would have the code for a newmolecule. that is just what happens in nature, except that nature does it really quickly—inonly a matter of seconds, which is quite a feat.

most of the time our dna replicates with dutiful accuracy, but just occasionally—aboutone time in a million—a letter gets into the wrong place. this is known as a single nucleotidepolymorphism, or snp, familiarly known to biochemists as a “snip.” generally these snipsare buried in stretches of noncoding dna and have no detectable consequence for the body.

but occasionally they make a difference. they might leave you predisposed to some disease,but equally they might confer some slight advantage—more protective pigmentation, forinstance, or increased production of red blood cells for someone living at altitude. over time,these slight modifications accumulate in both individuals and in populations, contributing tothe distinctiveness of both.

the balance between accuracy and errors in replication is a fine one. too many errors andthe organism can’t function, but too few and it sacrifices adaptability. a similar balance mustexist between stability in an organism and innovation. an increase in red blood cells can helpa person or group living at high elevations to move and breathe more easily because more redcells can carry more oxygen. but additional red cells also thicken the blood. add too many,and “it’s like pumping oil,” in the words of temple university anthropologist charles weitz.

that’s hard on the heart. thus those designed to live at high altitude get increased breathingefficiency, but pay for it with higher-risk hearts. by such means does darwinian naturalselection look after us. it also helps to explain why we are all so similar. evolution simplywon’t let you become too different—not without becoming a new species anyway.

the 0.1 percent difference between your genes and mine is accounted for by our snips.

now if you compared your dna with a third person’s, there would also be 99.9 percentcorrespondence, but the snips would, for the most part, be in different places. add more
people to the comparison and you will get yet more snips in yet more places. for every one ofyour 3.2 billion bases, somewhere on the planet there will be a person, or group of persons,with different coding in that position. so not only is it wrong to refer to “the” human genome,but in a sense we don’t even have “a” human genome. we have six billion of them. we are all99.9 percent the same, but equally, in the words of the biochemist david cox, “you could sayall humans share nothing, and that would be correct, too.”

but we have still to explain why so little of that dna has any discernible purpose. it startsto get a little unnerving, but it does really seem that the purpose of life is to perpetuate dna.

the 97 percent of our dna commonly called junk is largely made up of clumps of lettersthat, in ridley’s words, “exist for the pure and simple reason that they are good at gettingthemselves duplicated.”

2most of your dna, in other words, is not devoted to you but toitself: you are a machine for reproducing it, not it for you. life, you will recall, just wants tobe, and dna is what makes it so.

even when dna includes instructions for making genes—when it codes for them, asscientists put it—it is not necessarily with the smooth functioning of the organism in mind.

one of the commonest genes we have is for a protein called reverse transcriptase, which hasno known beneficial function in human beings at all. the one thing itdoes do is make itpossible for retroviruses, such as the aids virus, to slip unnoticed into the human system.

in other words, our bodies devote considerable energies to producing a protein that doesnothing that is beneficial and sometimes clobbers us. our bodies have no choice but to do sobecause the genes order it. we are vessels for their whims. altogether, almost half of humangenes—the largest proportion yet found in any organism—don’t do anything at all, as far aswe can tell, except reproduce themselves.

all organisms are in some sense slaves to their genes. that’s why salmon and spiders andother types of creatures more or less beyond counting are prepared to die in the process ofmating. the desire to breed, to disperse one’s genes, is the most powerful impulse in nature.

as sherwin b. nuland has put it: “empires fall, ids explode, great symphonies are written,and behind all of it is a single instinct that demands satisfaction.” from an evolutionary pointof view, sex is really just a reward mechanism to encourage us to pass on our genetic material.

scientists had only barely absorbed the surprising news that most of our dna doesn’t doanything when even more unexpected findings began to turn up. first in germany and then inswitzerland researchers performed some rather bizarre experiments that produced curiouslyunbizarre outcomes. in one they took the gene that controlled the development of a mouse’seye and inserted it into the larva of a fruit fly. the thought was that it might producesomething interestingly grotesque. in fact, the mouse-eye gene not only made a viable eye inthe fruit fly, it made a fly’s eye. here were two creatures that hadn’t shared a commonancestor for 500 million years, yet could swap genetic material as if they were sisters.

the story was the same wherever researchers looked. they found that they could inserthuman dna into certain cells of flies, and the flies would accept it as if it were their own.

2junk dna does have a use. it is the portion employed in dna fingerprinting. its practicality for this purposewas discovered accidentally by alec jeffreys, a scientist at the university of leicester in england. in 1986jeffreys was studying dna sequences for genetic markers associated with heritable diseases when he wasapproached by the police and asked if he could help connect a suspect to two murders. he realized his techniqueought to work perfectly for solving criminal cases-and so it proved. a young baker with the improbable name ofcolin pitchfork was sentenced to two life terms in prison for the murders.

over 60 percent of human genes, it turns out, are fundamentally the same as those found infruit flies. at least 90 percent correlate at some level to those found in mice. (we even havethe same genes for making a tail, if only they would switch on.) in field after field,researchers found that whatever organism they were working on—whether nematode wormsor human beings—they were often studying essentially the same genes. life, it appeared, wasdrawn up from a single set of blueprints.

further probings revealed the existence of a clutch of master control genes, each directingthe development of a section of the body, which were dubbed homeotic (from a greek wordmeaning “similar”) or hox genes. hox genes answered the long-bewildering question of howbillions of embryonic cells, all arising from a single fertilized egg and carrying identicaldna, know where to go and what to do—that this one should become a liver cell, this one astretchy neuron, this one a bubble of blood, this one part of the shimmer on a beating wing. itis the hox genes that instruct them, and they do it for all organisms in much the same way.

interestingly, the amount of genetic material and how it is organized doesn’t necessarily, oreven generally, reflect the level of sophistication of the creature that contains it. we haveforty-six chromosomes, but some ferns have more than six hundred. the lungfish, one of theleast evolved of all complex animals, has forty times as much dna as we have. even thecommon newt is more genetically splendorous than we are, by a factor of five.

clearly it is not the number of genes you have, but what you do with them. this is a verygood thing because the number of genes in humans has taken a big hit lately. until recently itwas thought that humans had at least 100,000 genes, possibly a good many more, but thatnumber was drastically reduced by the first results of the human genome project, whichsuggested a figure more like 35,000 or 40,000 genes—about the same number as are found ingrass. that came as both a surprise and a disappointment.

it won’t have escaped your attention that genes have been commonly implicated in anynumber of human frailties. exultant scientists have at various times declared themselves tohave found the genes responsible for obesity, schizophrenia, homosexuality, criminality,violence, alcoholism, even shoplifting and homelessness. perhaps the apogee (or nadir) of thisfaith in biodeterminism was a study published in the journal science in 1980 contending thatwomen are genetically inferior at mathematics. in fact, we now know, almost nothing aboutyou is so accommodatingly simple.

this is clearly a pity in one important sense, for if you had individual genes that determinedheight or propensity to diabetes or to baldness or any other distinguishing trait, then it wouldbe easy—comparatively easy anyway—to isolate and tinker with them. unfortunately, thirty-five thousand genes functioning independently is not nearly enough to produce the kind ofphysical complexity that makes a satisfactory human being. genes clearly therefore mustcooperate. a few disorders—hemophilia, parkinson’s disease, huntington’s disease, andcystic fibrosis, for example—are caused by lone dysfunctional genes, but as a rule disruptivegenes are weeded out by natural selection long before they can become permanentlytroublesome to a species or population. for the most part our fate and comfort—and even oureye color—are determined not by individual genes but by complexes of genes working inalliance. that’s why it is so hard to work out how it all fits together and why we won’t beproducing designer babies anytime soon.

in fact, the more we have learned in recent years the more complicated matters have tendedto become. even thinking, it turns out, affects the ways genes work. how fast a man’s beard
grows, for instance, is partly a function of how much he thinks about sex (because thinkingabout sex produces a testosterone surge). in the early 1990s, scientists made an even moreprofound discovery when they found they could knock out supposedly vital genes fromembryonic mice, and the mice were not only often born healthy, but sometimes were actuallyfitter than their brothers and sisters who had not been tampered with. when certain importantgenes were destroyed, it turned out, others were stepping in to fill the breach. this wasexcellent news for us as organisms, but not so good for our understanding of how cells worksince it introduced an extra layer of complexity to something that we had barely begun tounderstand anyway.

it is largely because of these complicating factors that cracking the human genome becameseen almost at once as only a beginning. the genome, as eric lander of mit has put it, is likea parts list for the human body: it tells us what we are made of, but says nothing about howwe work. what’s needed now is the operating manual—instructions for how to make it go.

we are not close to that point yet.

so now the quest is to crack the human proteome—a concept so novel that the termproteome didn’t even exist a decade ago. the proteome is the library of information thatcreates proteins. “unfortunately,” observed scientific american in the spring of 2002, “theproteome is much more complicated than the genome.”

that’s putting it mildly. proteins, you will remember, are the workhorses of all livingsystems; as many as a hundred million of them may be busy in any cell at any moment. that’sa lot of activity to try to figure out. worse, proteins’ behavior and functions are based notsimply on their chemistry, as with genes, but also on their shapes. to function, a protein mustnot only have the necessary chemical components, properly assembled, but then must also befolded into an extremely specific shape. “folding” is the term that’s used, but it’s amisleading one as it suggests a geometrical tidiness that doesn’t in fact apply. proteins loopand coil and crinkle into shapes that are at once extravagant and complex. they are more likefuriously mangled coat hangers than folded towels.

moreover, proteins are (if i may be permitted to use a handy archaism) the swingers of thebiological world. depending on mood and metabolic circumstance, they will allowthemselves to be phosphorylated, glycosylated, acetylated, ubiquitinated, farneysylated,sulfated, and linked to glycophosphatidylinositol anchors, among rather a lot else. often ittakes relatively little to get them going, it appears. drink a glass of wine, as scientificamerican notes, and you materially alter the number and types of proteins at large in yoursystem. this is a pleasant feature for drinkers, but not nearly so helpful for geneticists who aretrying to understand what is going on.

it can all begin to seem impossibly complicated, and in some ways itis impossiblycomplicated. but there is an underlying simplicity in all this, too, owing to an equallyelemental underlying unity in the way life works. all the tiny, deft chemical processes thatanimate cells—the cooperative efforts of nucleotides, the transcription of dna into rna—evolved just once and have stayed pretty well fixed ever since across the whole of nature. asthe late french geneticist jacques monod put it, only half in jest: “anything that is true of e. coli must be true of elephants, except more so.”

every living thing is an elaboration on a single original plan. as humans we are mereincrements—each of us a musty archive of adjustments, adaptations, modifications, andprovidential tinkerings stretching back 3.8 billion years. remarkably, we are even quite closely related to fruit and vegetables. about half the chemical functions that take place in abanana are fundamentally the same as the chemical functions that take place in you.

it cannot be said too often: all life is one. that is, and i suspect will forever prove to be, themost profound true statement there is.

part  vi the road to us

descended from the apes! my dear,let us hope that it is not true, but if it is,let us pray that it will not become generally known.

-remark attributed to the wife of the bishop of Worcester after Darwin’s theory of evolution was explained to her

27    ICE TIME

i had a dream, which was notall a dream.

the bright sun wasextinguish’d, and the starsdid wander . . . —Byron, “darkness”

in 1815 on the island of sumbawa in indonesia, a handsome and long-quiescent mountainnamed tambora exploded spectacularly, killing a hundred thousand people with its blast andassociated tsunamis. it was the biggest volcanic explosion in ten thousand years—150 timesthe size of mount st. helens, equivalent to sixty thousand hiroshima-sized atom bombs.

news didn’t travel terribly fast in those days. in london, the times ran a small story—actually a letter from a merchant—seven months after the event. but by this time tambora’seffects were already being felt. thirty-six cubic miles of smoky ash, dust, and grit haddiffused through the atmosphere, obscuring the sun’s rays and causing the earth to cool.

sunsets were unusually but blearily colorful, an effect memorably captured by the artist j. m.

1. turner, who could not have been happier, but mostly the world existed under anoppressive, dusky pall. it was this deathly dimness that inspired the byron lines above.

spring never came and summer never warmed: 1816 became known as the year withoutsummer. crops everywhere failed to grow. in ireland a famine and associated typhoidepidemic killed sixty-five thousand people. in new england, the year became popularlyknown as eighteen hundred and froze to death. morning frosts continued until june andalmost no planted seed would grow. short of fodder, livestock died or had to be prematurelyslaughtered. in every way it was a dreadful year—almost certainly the worst for farmers inmodern times. yet globally the temperature fell by only about 1.5 degrees fahrenheit. earth’snatural thermostat, as scientists would learn, is an exceedingly delicate instrument.

the nineteenth century was already a chilly time. for two hundred years europe and northamerica in particular had experienced a little ice age, as it has become known, whichpermitted all kinds of wintry events—frost fairs on the thames, ice-skating races along dutchcanals—that are mostly impossible now. it was a period, in other words, when frigidity wasmuch on people’s minds. so we may perhaps excuse nineteenth-century geologists for beingslow to realize that the world they lived in was in fact balmy compared with former epochs,and that much of the land around them had been shaped by crushing glaciers and cold thatwould wreck even a frost fair.

they knew there was something odd about the past. the european landscape was litteredwith inexplicable anomalies—the bones of arctic reindeer in the warm south of france, hugerocks stranded in improbable places—and they often came up with inventive but not terribly
plausible explanations. one french naturalist named de luc, trying to explain how graniteboulders had come to rest high up on the limestone flanks of the jura mountains, suggestedthat perhaps they had been shot there by compressed air in caverns, like corks out of apopgun. the term for a displaced boulder is an erratic, but in the nineteenth century theexpression seemed to apply more often to the theories than to the rocks.

the great british geologist arthur hallam has suggested that if james hutton, the father ofgeology, had visited switzerland, he would have seen at once the significance of the carvedvalleys, the polished striations, the telltale strand lines where rocks had been dumped, and theother abundant clues that point to passing ice sheets. unfortunately, hutton was not a traveler.

but even with nothing better at his disposal than secondhand accounts, hutton rejected out ofhand the idea that huge boulders had been carried three thousand feet up mountainsides byfloods—all the water in the world won’t make a boulder float, he pointed out—and becameone of the first to argue for widespread glaciation. unfortunately his ideas escaped notice, andfor another half century most naturalists continued to insist that the gouges on rocks could beattributed to passing carts or even the scrape of hobnailed boots.

local  peasants,  uncontaminated  by  scientific orthodoxy, knew better, however. thenaturalist jean de charpentier told the story of how in 1834 he was walking along a countrylane with a swiss woodcutter when they got to talking about the rocks along the roadside. thewoodcutter matter-of-factly told him that the boulders had come from the grimsel, a zone ofgranite some distance away. “when i asked him how he thought that these stones had reachedtheir location, he answered without hesitation: ‘the grimsel glacier transported them on bothsides of the valley, because that glacier extended in the past as far as the town of bern.’ ”

charpentier was delighted. he had come to such a view himself, but when he raised thenotion at scientific gatherings, it was dismissed. one of charpentier’s closest friends wasanother swiss naturalist, louis agassiz, who after some initial skepticism came to embrace,and eventually all but appropriate, the theory.

agassiz had studied under cuvier in paris and now held the post of professor of naturalhistory at the college of neuchatel in switzerland. another friend of agassiz’s, a botanistnamed karl schimper, was actually the first to coin the term ice age (in german eiszeit ), in1837, and to propose that there was good evidence to show that ice had once lain heavilyacross not just the swiss alps, but over much of europe, asia, and north america. it was aradical notion. he lent agassiz his notes—then came very much to regret it as agassizincreasingly got the credit for what schimper felt, with some legitimacy, was his theory.

charpentier likewise ended up a bitter enemy of his old friend. alexander von humboldt, yetanother friend, may have had agassiz at least partly in mind when he observed that there arethree stages in scientific discovery: first, people deny that it is true; then they deny that it isimportant; finally they credit the wrong person.

at all events, agassiz made the field his own. in his quest to understand the dynamics ofglaciation, he went everywhere—deep into dangerous crevasses and up to the summits of thecraggiest alpine peaks, often apparently unaware that he and his team were the first to climbthem. nearly everywhere agassiz encountered an unyielding reluctance to accept his theories.

humboldt urged him to return to his area of real expertise, fossil fish, and give up this madobsession with ice, but agassiz was a man possessed by an idea.

agassiz’s theory found even less support in britain, where most naturalists had never seena glacier and often couldn’t grasp the crushing forces that ice in bulk exerts. “could scratches
and polish just be due to ice ?” asked roderick murchison in a mocking tone at one meeting,evidently imagining the rocks as covered in a kind of light and glassy rime. to his dying day,he expressed the frankest incredulity at those “ice-mad” geologists who believed that glacierscould account for so much. william hopkins, a cambridge professor and leading member ofthe geological society, endorsed this view, arguing that the notion that ice could transportboulders presented “such obvious mechanical absurdities” as to make it unworthy of thesociety’s attention.

undaunted, agassiz traveled tirelessly to promote his theory. in 1840 he read a paper to ameeting of the british association for the advancement of science in glasgow at which hewas openly criticized by the great charles lyell. the following year the geological society ofedinburgh passed a resolution conceding that there might be some general merit in the theorybut that certainly none of it applied to scotland.

lyell did eventually come round. his moment of epiphany came when he realized that amoraine, or line of rocks, near his family estate in scotland, which he had passed hundreds oftimes, could only be understood if one accepted that a glacier had dropped them there. buthaving become converted, lyell then lost his nerve and backed off from public support of theice age idea. it was a frustrating time for agassiz. his marriage was breaking up, schimperwas hotly accusing him of the theft of his ideas, charpentier wouldn’t speak to him, and thegreatest living geologist offered support of only the most tepid and vacillating kind.

in 1846, agassiz traveled to america to give a series of lectures and there at last found theesteem he craved. harvard gave him a professorship and built him a first-rate museum, themuseum of comparative zoology. doubtless it helped that he had settled in new england,where the long winters encouraged a certain sympathy for the idea of interminable periods ofcold. it also helped that six years after his arrival the first scientific expedition to greenlandreported that nearly the whole of that semicontinent was covered in an ice sheet just like theancient one imagined in agassiz’s theory. at long last, his ideas began to find a realfollowing. the one central defect of agassiz’s theory was that his ice ages had no cause. butassistance was about to come from an unlikely quarter.

in the 1860s, journals and other learned publications in britain began to receive papers onhydrostatics, electricity, and other scientific subjects from a james croll of anderson’suniversity in glasgow. one of the papers, on how variations in earth’s orbit might haveprecipitated ice ages, was published in the philosophical magazine in 1864 and wasrecognized at once as a work of the highest standard. so there was some surprise, and perhapsjust a touch of embarrassment, when it turned out that croll was not an academic at theuniversity, but a janitor.

born in 1821, croll grew up poor, and his formal education lasted only to the age ofthirteen. he worked at a variety of jobs—as a carpenter, insurance salesman, keeper of atemperance hotel—before taking a position as a janitor at anderson’s (now the university ofstrathclyde) in glasgow. by somehow inducing his brother to do much of his work, he wasable to pass many quiet evenings in the university library teaching himself physics,mechanics, astronomy, hydrostatics, and the other fashionable sciences of the day, andgradually began to produce a string of papers, with a particular emphasis on the motions ofearth and their effect on climate.

croll was the first to suggest that cyclical changes in the shape of earth’s orbit, fromelliptical (which is to say slightly oval) to nearly circular to elliptical again, might explain the
onset and retreat of ice ages. no one had ever thought before to consider an astronomicalexplanation for variations in earth’s weather. thanks almost entirely to croll’s persuasivetheory, people in britain began to become more responsive to the notion that at some formertime parts of the earth had been in the grip of ice. when his ingenuity and aptitude wererecognized, croll was given a job at the geological survey of scotland and widely honored:

he was made a fellow of the royal society in london and of the new york academy ofscience and given an honorary degree from the university of st. andrews, among much else.

unfortunately, just as agassiz’s theory was at last beginning to find converts in europe, hewas busy taking it into ever more exotic territory in america. he began to find evidence forglaciers practically everywhere he looked, including near the equator. eventually he becameconvinced that ice had once covered the whole earth, extinguishing all life, which god hadthen re-created. none of the evidence agassiz cited supported such a view. nonetheless, inhis adopted country his stature grew and grew until he was regarded as only slightly below adeity. when he died in 1873 harvard felt it necessary to appoint three professors to take hisplace.

yet, as sometimes happens, his theories fell swiftly out of fashion. less than a decade afterhis death his successor in the chair of geology at harvard wrote that the “so-called glacialepoch . . . so popular a few years ago among glacial geologists may now be rejected withouthesitation.”

part of the problem was that croll’s computations suggested that the most recent ice ageoccurred eighty thousand years ago, whereas the geological evidence increasingly indicatedthat earth had undergone some sort of dramatic perturbation much more recently than that.

without a plausible explanation for what might have provoked an ice age, the whole theoryfell into abeyance. there it might have remained for some time except that in the early 1900sa serbian academic named milutin milankovitch, who had no background in celestial motionsat all—he was a mechanical engineer by training—developed an unexpected interest in thematter. milankovitch realized that the problem with croll’s theory was not that it wasincorrect but that it was too simple.

as earth moves through space, it is subject not just to variations in the length and shape ofits orbit, but also to rhythmic shifts in its angle of orientation to the sun—its tilt and pitch andwobble—all affecting the length and intensity of sunlight falling on any patch of land. inparticular it is subject to three changes in position, known formally as its obliquity,precession, and eccentricity, over long periods of time. milankovitch wondered if there mightbe a relationship between these complex cycles and the comings and goings of ice ages. thedifficulty was that the cycles were of widely different lengths—of approximately 20,000,40,000, and 100,000 years, but varying in each case by up to a few thousand years—whichmeant that determining their points of intersection over long spans of time involved a nearlyendless amount of devoted computation. essentially milankovitch had to work out the angleand duration of incoming solar radiation at every latitude on earth, in every season, for amillion years, adjusted for three ever-changing variables.

happily  this  was  precisely  the  sort  of repetitive toil that suited milankovitch’stemperament. for the next twenty years, even while on vacation, he worked ceaselessly withpencil and slide rule computing the tables of his cycles—work that now could be completed ina day or two with a computer. the calculations all had to be made in his spare time, but in1914 milankovitch suddenly got a great deal of that when world war i broke out and he wasarrested owing to his position as a reservist in the serbian army. he spent most of the next
four years under loose house arrest in budapest, required only to report to the police once aweek. the rest of his time was spent working in the library of the hungarian academy ofsciences. he was possibly the happiest prisoner of war in history.

the  eventual  outcome  of  his diligent scribblings was the 1930 book mathematicalclimatology and the astronomical theory of climatic changes. milankovitch was right thatthere was a relationship between ice ages and planetary wobble, though like most people heassumed that it was a gradual increase in harsh winters that led to these long spells ofcoldness. it was a russian-german meteorologist, wladimir k?ppen—father-in-law of ourtectonic friend alfred wegener—who saw that the process was more subtle, and rather moreunnerving, than that.

the cause of ice ages, k?ppen decided, is to be found in cool summers, not brutal winters.

if summers are too cool to melt all the snow that falls on a given area, more incoming sunlightis bounced back by the reflective surface, exacerbating the cooling effect and encouraging yetmore snow to fall. the consequence would tend to be self-perpetuating. as snow accumulatedinto an ice sheet, the region would grow cooler, prompting more ice to accumulate. as theglaciologist gwen schultz has noted: “it is not necessarily the amount of snow that causes icesheets but the fact that snow, however little, lasts.” it is thought that an ice age could startfrom a single unseasonal summer. the leftover snow reflects heat and exacerbates the chillingeffect. “the process is self-enlarging, unstoppable, and once the ice is really growing itmoves,” says mcphee. you have advancing glaciers and an ice age.

in the 1950s, because of imperfect dating technology, scientists were unable to correlatemilankovitch’s carefully worked-out cycles with the supposed dates of ice ages as thenperceived, and so milankovitch and his calculations increasingly fell out of favor. he died in1958, unable to prove that his cycles were correct. by this time, write john and mary gribbin,“you would have been hard pressed to find a geologist or meteorologist who regarded themodel as being anything more than an historical curiosity.” not until the 1970s and therefinement of a potassium-argon method for dating ancient seafloor sediments were histheories finally vindicated.

the milankovitch cycles alone are not enough to explain cycles of ice ages. many otherfactors are involved—not least the disposition of the continents, in particular the presence oflandmasses over the poles—but the specifics of these are imperfectly understood. it has beensuggested, however, that if you hauled north america, eurasia, and greenland just threehundred miles north we would have permanent and inescapable ice ages. we are very lucky, itappears, to get any good weather at all. even less well understood are the cycles ofcomparative balminess within ice ages, known as interglacials. it is mildly unnerving toreflect that the whole of meaningful human history—the development of farming, the creationof towns, the rise of mathematics and writing and science and all the rest—has taken placewithin an atypical patch of fair weather. previous interglacials have lasted as little as eightthousand years. our own has already passed its ten thousandth anniversary.

the fact is, we are still very much in an ice age; it’s just a somewhat shrunken one—thoughless shrunken than many people realize. at the height of the last period of glaciation, aroundtwenty thousand years ago, about 30 percent of the earth’s land surface was under ice. tenpercent still is—and a further 14 percent is in a state of permafrost. three-quarters of all thefresh water on earth is locked up in ice even now, and we have ice caps at both poles—asituation that may be unique in earth’s history. that there are snowy winters through much of
the world and permanent glaciers even in temperate places such as new zealand may seemquite natural, but in fact it is a most unusual situation for the planet.

for most of its history until fairly recent times the general pattern for earth was to be hotwith no permanent ice anywhere. the current ice age—ice epoch really—started about fortymillion years ago, and has ranged from murderously bad to not bad at all. ice ages tend towipe out evidence of earlier ice ages, so the further back you go the more sketchy the picturegrows, but it appears that we have had at least seventeen severe glacial episodes in the last 2.5million years or so—the period that coincides with the rise of homo erectus in africafollowed by modern humans. two commonly cited culprits for the present epoch are the riseof the himalayas and the formation of the isthmus of panama, the first disrupting air flows,the second ocean currents. india, once an island, has pushed two thousand kilometers into theasian landmass over the last forty-five million years, raising not only the himalayas, but alsothe vast tibetan plateau behind them. the hypothesis is that the higher landscape was notonly cooler, but diverted winds in a way that made them flow north and toward northamerica, making it more susceptible to long-term chills. then, beginning about five millionyears ago, panama rose from the sea, closing the gap between north and south america,disrupting the flows of warming currents between the pacific and atlantic, and changingpatterns of precipitation across at least half the world. one consequence was a drying out ofafrica, which caused apes to climb down out of trees and go looking for a new way of livingon the emerging savannas.

at all events, with the oceans and continents arranged as they are now, it appears that icewill be a long-term part of our future. according to john mcphee, about fifty more glacialepisodes can be expected, each lasting a hundred thousand years or so, before we can hope fora really long thaw.

before fifty million years ago, earth had no regular ice ages, but when we did have themthey tended to be colossal. a massive freezing occurred about 2.2 billion years ago, followedby a billion years or so of warmth. then there was another ice age even larger than the first—so large that some scientists are now referring to the age in which it occurred as thecryogenian, or super ice age. the condition is more popularly known as snowball earth.

“snowball,” however, barely captures the murderousness of conditions. the theory is thatbecause of a fall in solar radiation of about 6 percent and a dropoff in the production (orretention) of greenhouse gases, earth essentially lost its ability to hold on to its heat. itbecame a kind of all-over antarctica. temperatures plunged by as much as 80 degreesfahrenheit. the entire surface of the planet may have frozen solid, with ocean ice up to half amile thick at higher latitudes and tens of yards thick even in the tropics.

there is a serious problem in all this in that the geological evidence indicates iceeverywhere, including around the equator, while the biological evidence suggests just asfirmly that there must have been open water somewhere. for one thing, cyanobacteriasurvived the experience, and they photosynthesize. for that they needed sunlight, but as youwill know if you have ever tried to peer through it, ice quickly becomes opaque and after onlya few yards would pass on no light at all. two possibilities have been suggested. one is that alittle ocean water did remain exposed (perhaps because of some kind of localized warming ata hot spot); the other is that maybe the ice formed in such a way that it remained translucent—a condition that does sometimes happen in nature.

if earth did freeze over, then there is the very difficult question of how it ever got warmagain. an icy planet should reflect so much heat that it would stay frozen forever. it appearsthat rescue may have come from our molten interior. once again, we may be indebted totectonics for allowing us to be here. the idea is that we were saved by volcanoes, whichpushed through the buried surface, pumping out lots of heat and gases that melted the snowsand re-formed the atmosphere. interestingly, the end of this hyper-frigid episode is marked bythe cambrian outburst—the springtime event of life’s history. in fact, it may not have been astranquil as all that. as earth warmed, it probably had the wildest weather it has everexperienced, with hurricanes powerful enough to raise waves to the heights of skyscrapersand rainfalls of indescribable intensity.

throughout all this the tubeworms and clams and other life forms adhering to deep oceanvents undoubtedly went on as if nothing were amiss, but all other life on earth probably cameas close as it ever has to checking out entirely. it was all a long time ago and at this stage wejust don’t know.

compared with a cryogenian outburst, the ice ages of more recent times seem pretty smallscale, but of course they were immensely grand by the standards of anything to be found onearth today. the wisconsian ice sheet, which covered much of europe and north america,was two miles thick in places and marched forward at a rate of about four hundred feet a year.

what a thing it must have been to behold. even at their leading edge, the ice sheets could benearly half a mile thick. imagine standing at the base of a wall of ice two thousand feet high.

behind this edge, over an area measuring in the millions of square miles, would be nothingbut more ice, with only a few of the tallest mountain summits poking through. wholecontinents sagged under the weight of so much ice and even now, twelve thousand years afterthe glaciers’ withdrawal, are still rising back into place. the ice sheets didn’t just dribble outboulders and long lines of gravelly moraines, but dumped entire landmasses—long islandand cape cod and nantucket, among others—as they slowly swept along. it’s little wonderthat geologists before agassiz had trouble grasping their monumental capacity to reworklandscapes.

if ice sheets advanced again, we have nothing in our armory that could deflect them. in1964, at prince william sound in alaska, one of the largest glacial fields in north americawas hit by the strongest earthquake ever recorded on the continent. it measured 9.2 on therichter scale. along the fault line, the land rose by as much as twenty feet. the quake was soviolent, in fact, that it made water slosh out of pools in texas. and what effect did thisunparalleled outburst have on the glaciers of prince william sound? none at all. they justsoaked it up and kept on moving.

for a long time it was thought that we moved into and out of ice ages gradually, overhundreds of thousands of years, but we now know that that has not been the case. thanks toice cores from greenland we have a detailed record of climate for something over a hundredthousand years, and what is found there is not comforting. it shows that for most of its recenthistory earth has been nothing like the stable and tranquil place that civilization has known,but rather has lurched violently between periods of warmth and brutal chill.

toward the end of the last big glaciation, some twelve thousand years ago, earth began towarm, and quite rapidly, but then abruptly plunged back into bitter cold for a thousand yearsor so in an event known to science as the younger dryas. (the name comes from the arcticplant the dryas, which is one of the first to recolonize land after an ice sheet withdraws. therewas also an older dryas period, but it wasn’t so sharp.) at the end of this thousand-year
onslaught average temperatures leapt again, by as much as seven degrees in twenty years,which doesn’t sound terribly dramatic but is equivalent to exchanging the climate ofscandinavia for that of the mediterranean in just two decades. locally, changes have beeneven more dramatic. greenland ice cores show the temperatures there changing by as much asfifteen degrees in ten years, drastically altering rainfall patterns and growing conditions. thismust have been unsettling enough on a thinly populated planet. today the consequenceswould be pretty well unimaginable.

what is most alarming is that we have no idea—none—what natural phenomena could soswiftly rattle earth’s thermometer. as elizabeth kolbert, writing in the new yorker, hasobserved: “no known external force, or even any that has been hypothesized, seems capableof yanking the temperature back and forth as violently, and as often, as these cores haveshown to be the case.” there seems to be, she adds, “some vast and terrible feedback loop,”

probably involving the oceans and disruptions of the normal patterns of ocean circulation, butall this is a long way from being understood.

one theory is that the heavy inflow of meltwater to the seas at the beginning of theyounger dryas reduced the saltiness (and thus density) of northern oceans, causing the gulfstream to swerve to the south, like a driver trying to avoid a collision. deprived of the gulfstream’s warmth, the northern latitudes returned to chilly conditions. but this doesn’t begin toexplain why a thousand years later when the earth warmed once again the gulf stream didn’tveer as before. instead, we were given the period of unusual tranquility known as theholocene, the time in which we live now.

there is no reason to suppose that this stretch of climatic stability should last much longer.

in fact, some authorities believe that we are in for even worse than what went before. it isnatural to suppose that global warming would act as a useful counterweight to the earth’stendency to plunge back into glacial conditions. however, as kolbert has pointed out, whenyou are confronted with a fluctuating and unpredictable climate “the last thing you’d want todo is conduct a vast unsupervised experiment on it.” it has even been suggested, with moreplausibility than would at first seem evident, that an ice age might actually be induced by arise in temperatures. the idea is that a slight warming would enhance evaporation rates andincrease cloud cover, leading in the higher latitudes to more persistent accumulations of snow.

in fact, global warming could plausibly, if paradoxically, lead to powerful localized cooling innorth america and northern europe.

climate is the product of so many variables—rising and falling carbon dioxide levels, theshifts of continents, solar activity, the stately wobbles of the milankovitch cycles—that it is asdifficult to comprehend the events of the past as it is to predict those of the future. much issimply beyond us. take antarctica. for at least twenty million years after it settled over thesouth pole antarctica remained covered in plants and free of ice. that simply shouldn’t havebeen possible.

no less intriguing are the known ranges of some late dinosaurs. the british geologiststephen drury notes that forests within 10 degrees latitude of the north pole were home togreat beasts, including tyrannosaurus rex. “that is bizarre,” he writes, “for such a highlatitude is continually dark for three months of the year.” moreover, there is now evidencethat these high latitudes suffered severe winters. oxygen isotope studies suggest that theclimate around fairbanks, alaska, was about the same in the late cretaceous period as it isnow. so what was tyrannosaurus doing there? either it migrated seasonally over enormousdistances or it spent much of the year in snowdrifts in the dark. in australia—which at that
time was more polar in its orientation—a retreat to warmer climes wasn’t possible. howdinosaurs managed to survive in such conditions can only be guessed.

one thought to bear in mind is that if the ice sheets did start to form again for whateverreason, there is a lot more water for them to draw on this time. the great lakes, hudson bay,the countless lakes of canada—these weren’t there to fuel the last ice age. they were createdby it.

on the other hand, the next phase of our history could see us melting a lot of ice rather thanmaking it. if all the ice sheets melted, sea levels would rise by two hundred feet—the heightof a twenty-story building—and every coastal city in the world would be inundated. morelikely, at least in the short term, is the collapse of the west antarctic ice sheet. in the past fiftyyears the waters around it have warmed by 2.5 degrees centigrade, and collapses haveincreased dramatically. because of the underlying geology of the area, a large-scale collapseis all the more possible. if so, sea levels globally would rise—and pretty quickly—by betweenfifteen and twenty feet on average.

the extraordinary fact is that we don’t know which is more likely, a future offering us eonsof perishing frigidity or one giving us equal expanses of steamy heat. only one thing iscertain: we live on a knife edge.

in the long run, incidentally, ice ages are by no means bad news for the planet. they grindup rocks and leave behind new soils of sumptuous richness, and gouge out fresh water lakesthat provide abundant nutritive possibilities for hundreds of species of being. they act as aspur to migration and keep the planet dynamic. as tim flannery has remarked: “there is onlyone question you need ask of a continent in order to determine the fate of its people: ‘did youhave a good ice age?’ ” and with that in mind, it’s time to look at a species of ape that trulydid.

28    THE MYSTERIOUS BIPED

just before christmas 1887, a young dutch doctor with an un-dutch name, marieeugène fran?ois thomas dubois, arrived in sumatra, in the dutch east indies, with theintention of finding the earliest human remains on earth.

1 several things were extraordinary about this. to begin with, no one had ever gone lookingfor ancient human bones before. everything that had been found to this point had been foundaccidentally, and nothing in dubois’s background suggested that he was the ideal candidate tomake the process intentional. he was an anatomist by training with no background inpaleontology. nor was there any special reason to suppose that the east indies would holdearly human remains. logic dictated that if ancient people were to be found at all, it would beon a large and long-populated landmass, not in the comparative fastness of an archipelago.

dubois was driven to the east indies on nothing stronger than a hunch, the availability ofemployment, and the knowledge that sumatra was full of caves, the environment in whichmost of the important hominid fossils had so far been found. what is most extraordinary in allthis—nearly miraculous, really—is that he found what he was looking for.

at the time dubois conceived his plan to search for a missing link, the human fossil recordconsisted of very little: five incomplete neandertal skeletons, one partial jawbone of uncertainprovenance, and a half-dozen ice-age humans recently found by railway workers in a cave at acliff called cro-magnon near les eyzies, france. of the neandertal specimens, the bestpreserved was sitting unremarked on a shelf in london. it had been found by workers blastingrock from a quarry in gibraltar in 1848, so its preservation was a wonder, but unfortunatelyno one yet appreciated what it was. after being briefly described at a meeting of the gibraltarscientific society, it had been sent to the hunterian museum in london, where it remainedundisturbed but for an occasional light dusting for over half a century. the first formaldescription of it wasn’t written until 1907, and then by a geologist named william sollas“with only a passing competency in anatomy.”

so instead the name and credit for the discovery of the first early humans went to theneander valley in germany—not unfittingly, as it happens, for by uncanny coincidenceneander in greek means “new man.” there in 1856 workmen at another quarry, in a cliff faceoverlooking the düssel river, found some curious-looking bones, which they passed to alocal schoolteacher, knowing he had an interest in all things natural. to his great credit theteacher, johann karl fuhlrott, saw that he had some new type of human, though quite what itwas, and how special, would be matters of dispute for some time.

many people refused to accept that the neandertal bones were ancient at all. august mayer,a professor at the university of bonn and a man of influence, insisted that the bones were1though dutch, dubois was from eijsden, a town bordering the french-speaking part of belgium.

merely those of a mongolian cossack soldier who had been wounded while fighting ingermany in 1814 and had crawled into the cave to die. hearing of this, t. h. huxley inengland drily observed how remarkable it was that the soldier, though mortally wounded, hadclimbed sixty feet up a cliff, divested himself of his clothing and personal effects, sealed thecave opening, and buried himself under two feet of soil. another anthropologist, puzzlingover the neandertal’s heavy brow ridge, suggested that it was the result of long-term frowningarising from a poorly healed forearm fracture. (in their eagerness to reject the idea of earlierhumans, authorities were often willing to embrace the most singular possibilities. at about thetime that dubois was setting out for sumatra, a skeleton found in périgueux was confidentlydeclared to be that of an eskimo. quite what an ancient eskimo was doing in southwestfrance was never comfortably explained. it was actually an early cro-magnon.)it was against this background that dubois began his search for ancient human bones. hedid no digging himself, but instead used fifty convicts lent by the dutch authorities. for a yearthey worked on sumatra, then transferred to java. and there in 1891, dubois—or rather histeam, for dubois himself seldom visited the sites—found a section of ancient human craniumnow known as the trinil skullcap. though only part of a skull, it showed that the owner hadhad distinctly nonhuman features but a much larger brain than any ape. dubois called itanthropithecus erectus (later changed for technical reasons to pithecanthropus erectus) anddeclared it the missing link between apes and humans. it quickly became popularized as “javaman.” today we know it as homo erectus.

the next year dubois’s workers found a virtually complete thighbone that lookedsurprisingly modern. in fact, many anthropologists think itis modern, and has nothing to dowith java man. if it is an erectus bone, it is unlike any other found since. nonetheless duboisused the thighbone to deduce—correctly, as it turned out—that pithecanthropus walkedupright. he also produced, with nothing but a scrap of cranium and one tooth, a model of thecomplete skull, which also proved uncannily accurate.

in 1895, dubois returned to europe, expecting a triumphal reception. in fact, he met nearlythe opposite reaction. most scientists disliked both his conclusions and the arrogant manner inwhich he presented them. the skullcap, they said, was that of an ape, probably a gibbon, andnot of any early human. hoping to bolster his case, in 1897 dubois allowed a respectedanatomist from the university of strasbourg, gustav schwalbe, to make a cast of the skullcap.

to dubois’s dismay, schwalbe thereupon produced a monograph that received far moresympathetic attention than anything dubois had written and followed with a lecture tour inwhich he was celebrated nearly as warmly as if he had dug up the skull himself. appalled andembittered, dubois withdrew into an undistinguished position as a professor of geology at theuniversity of amsterdam and for the next two decades refused to let anyone examine hisprecious fossils again. he died in 1940 an unhappy man.

meanwhile, and half a world away, in late 1924 raymond dart, the australian-born head ofanatomy at the university of the witwatersrand in johannesburg, was sent a small butremarkably complete skull of a child, with an intact face, a lower jaw, and what is known asan endocast—a natural cast of the brain—from a limestone quarry on the edge of the kalaharidesert at a dusty spot called taung. dart could see at once that the taung skull was not of ahomo erectus like dubois’s java man, but from an earlier, more apelike creature. he placedits age at two million years and dubbed it australopithecus africanus, or “southern ape man ofafrica.” in a report to nature, dart called the taung remains “amazingly human” and
suggested the need for an entirely new family, homo simiadae (“the man-apes”), toaccommodate the find.

the authorities were even less favorably disposed to dart than they had been to dubois.

nearly everything about his theory—indeed, nearly everything about dart, it appears—annoyed them. first he had proved himself lamentably presumptuous by conducting theanalysis himself rather than calling on the help of more worldly experts in europe. even hischosen name, australopithecus, showed a lack of scholarly application, combining as it didgreek and latin roots. above all, his conclusions flew in the face of accepted wisdom.

humans and apes, it was agreed, had split apart at least fifteen million years ago in asia. ifhumans had arisen in africa, why, that would make us negroid, for goodness sake. it wasrather as if someone working today were to announce that he had found the ancestral bones ofhumans in, say, missouri. it just didn’t fit with what was known.

dart’s sole supporter of note was robert broom, a scottish-born physician andpaleontologist of considerable intellect and cherishably eccentric nature. it was broom’shabit, for instance, to do his fieldwork naked when the weather was warm, which was often.

he was also known for conducting dubious anatomical experiments on his poorer and moretractable patients. when the patients died, which was also often, he would sometimes burytheir bodies in his back garden to dig up for study later.

broom was an accomplished paleontologist, and since he was also resident in south africahe was able to examine the taung skull at first hand. he could see at once that it was asimportant as dart supposed and spoke out vigorously on dart’s behalf, but to no effect. forthe next fifty years the received wisdom was that the taung child was an ape and nothingmore. most textbooks didn’t even mention it. dart spent five years working up a monograph,but could find no one to publish it. eventually he gave up the quest to publish altogether(though he did continue hunting for fossils). for years, the skull—today recognized as one ofthe supreme treasures of anthropology—sat as a paperweight on a colleague’s desk.

at the time dart made his announcement in 1924, only four categories of ancient hominidwere known—homo heidelbergensis, homo rhodesiensis, neandertals, and dubois’s javaman—but all that was about to change in a very big way.

first, in china, a gifted canadian amateur named davidson black began to poke around ata place, dragon bone hill, that was locally famous as a hunting ground for old bones.

unfortunately, rather than preserving the bones for study, the chinese ground them up tomake medicines. we can only guess how many priceless homo erectus bones ended up as asort of chinese equivalent of bicarbonate of soda. the site had been much denuded by thetime black arrived, but he found a single fossilized molar and on the basis of that alone quitebrilliantly announced the discovery of sinanthropus pekinensis, which quickly became knownas peking man.

at black’s urging, more determined excavations were undertaken and many other bonesfound. unfortunately all were lost the day after the japanese attack on pearl harbor in 1941when a contingent of u.s. marines, trying to spirit the bones (and themselves) out of thecountry, was intercepted by the japanese and imprisoned. seeing that their crates held nothingbut bones, the japanese soldiers left them at the roadside. it was the last that was ever seen ofthem.

in the meantime, back on dubois’s old turf of java, a team led by ralph von koenigswaldhad found another group of early humans, which became known as the solo people from thesite of their discovery on the solo river at ngandong. koenigswald’s discoveries might havebeen more impressive still but for a tactical error that was realized too late. he had offeredlocals ten cents for every piece of hominid bone they could come up with, then discovered tohis horror that they had been enthusiastically smashing large pieces into small ones tomaximize their income.

in the following years as more bones were found and identified there came a flood of newnames—homo aurignacensis, australopithecus transvaalensis, paranthropus crassidens,zinjanthropus boisei,and scores of others, nearly all involving a new genus type as well as anew species. by the 1950s, the number of named hominid types had risen to comfortably overa hundred. to add to the confusion, individual forms often went by a succession of differentnames as paleoanthropologists refined, reworked, and squabbled over classifications. solopeople were known variously as homo soloensis, homo primigenius asiaticus, homoneanderthalensis soloensis, homo sapiens soloensis, homo erectus erectus, and, finally, plainhomo erectus .

in an attempt to introduce some order, in 1960 f. clark howell of the university ofchicago, following the suggestions of ernst mayr and others the previous decade, proposedcutting the number of genera to just two—australopithecus and homo —and rationalizingmany of the species. the java and peking men both became homo erectus. for a time orderprevailed in the world of the hominids.

2 it didn’t last.

after about a decade of comparative calm, paleoanthropology embarked on another periodof swift and prolific discovery, which hasn’t abated yet. the 1960s produced homo habilis,thought by some to be the missing link between apes and humans, but thought by others not tobe a separate species at all. then came (among many others) homo ergaster, homolouisleakeyi, homo rudolfensis, homo microcranus, and homo antecessor, as well as a raft ofaustralopithecines: a.afarensis, a. praegens, a. ramidus, a. walkeri, a. anamensis, and stillothers. altogether, some twenty types of hominid are recognized in the literature today.

unfortunately, almost no two experts recognize the same twenty.

some continue to observe the two hominid genera suggested by howell in 1960, but othersplace some of the australopithecines in a separate genus called paranthropus , and still othersadd an earlier group called ardipithecus. some put praegens into australopithecus and someinto a new classification, homo antiquus, but most don’t recognize praegens as a separatespecies at all. there is no central authority that rules on these things. the only way a namebecomes accepted is by consensus, and there is often very little of that.

a big part of the problem, paradoxically, is a shortage of evidence. since the dawn of time,several billion human (or humanlike) beings have lived, each contributing a little geneticvariability to the total human stock. out of this vast number, the whole of our understandingof human prehistory is based on the remains, often exceedingly fragmentary, of perhaps fivethousand individuals. “you could fit it all into the back of a pickup truck if you didn’t mind2humans are put in the lamely homimdae. its members, traditionally called hominids, include any creatures(including extinct ones) that are more closely related to us than to any surviving chimpanzees. the apes,meanwhile, are lumped together in a family called pongidae. many authorities believe that chimps, gorillas, andorangutans should also be included in this family, with humans and chimps in a subfamily called homininae.

the upshot is that the creatures traditionally called hominids become, under this arrangement, hominins. (leakeyand others insist on that designation.) hominoidea is the name of the aue sunerfamily which includes us.

how much you jumbled everything up,” ian tattersall, the bearded and friendly curator ofanthropology at the american museum of natural history in new york, replied when i askedhim the size of the total world archive of hominid and early human bones.

the shortage wouldn’t be so bad if the bones were distributed evenly through time andspace, but of course they are not. they appear randomly, often in the most tantalizing fashion.

homo erectus walked the earth for well over a million years and inhabited territory from theatlantic edge of europe to the pacific side of china, yet if you brought back to life everyhomo erectus individual whose existence we can vouch for, they wouldn’t fill a school bus.

homo habilis consists of even less: just two partial skeletons and a number of isolated limbbones. something as short-lived as our own civilization would almost certainly not be knownfrom the fossil record at all.

“in europe,” tattersall offers by way of illustration, “you’ve got hominid skulls in georgiadated to about 1.7 million years ago, but then you have a gap of almost a million years beforethe next remains turn up in spain, right on the other side of the continent, and then you’ve gotanother 300,000-year gap before you get a homo heidelbergensis in germany—and none ofthem looks terribly much like any of the others.” he smiled. “it’s from these kinds offragmentary pieces that you’re trying to work out the histories of entire species. it’s quite atall order. we really have very little idea of the relationships between many ancient species—which led to us and which were evolutionary dead ends. some probably don’t deserve to beregarded as separate species at all.”

it is the patchiness of the record that makes each new find look so sudden and distinct fromall the others. if we had tens of thousands of skeletons distributed at regular intervals throughthe historical record, there would be appreciably more degrees of shading. whole new speciesdon’t emerge instantaneously, as the fossil record implies, but gradually out of other, existingspecies. the closer you go back to a point of divergence, the closer the similarities are, so thatit becomes exceedingly difficult, and sometimes impossible, to distinguish a late homoerectus from an early homo sapiens, since it is likely to be both and neither. similardisagreements can often arise over questions of identification from fragmentary remains—deciding, for instance, whether a particular bone represents a female australopithecus boiseior a male homo habilis.

with so little to be certain about, scientists often have to make assumptions based on otherobjects found nearby, and these may be little more than valiant guesses. as alan walker andpat shipman have drily observed, if you correlate tool discovery with the species of creaturemost often found nearby, you would have to conclude that early hand tools were mostly madeby antelopes.

perhaps nothing better typifies the confusion than the fragmentary bundle of contradictionsthat was homo habilis. simply put, habilis bones make no sense. when arranged in sequence,they show males and females evolving at different rates and in different directions—the malesbecoming less apelike and more human with time, while females from the same period appearto be moving away from humanness toward greater apeness. some authorities don’t believehabilis is a valid category at all. tattersall and his colleague jeffrey schwartz dismiss it as amere “wastebasket species”—one into which unrelated fossils “could be conveniently swept.”

even those who see habilis as an independent species don’t agree on whether it is of the samegenus as us or is from a side branch that never came to anything.

finally, but perhaps above all, human nature is a factor in all this. scientists have a naturaltendency to interpret finds in the way that most flatters their stature. it is a rare paleontologistindeed who announces that he has found a cache of bones but that they are nothing to getexcited about. or as john reader understatedly observes in the book missing links, “it isremarkable how often the first interpretations of new evidence have confirmed thepreconceptions of its discoverer.”

all this leaves ample room for arguments, of course, and nobody likes to argue more thanpaleoanthropologists. “and of all the disciplines in science, paleoanthropology boasts perhapsthe largest share of egos,” say the authors of the recent java man —a book, it may be noted,that itself devotes long, wonderfully unselfconscious passages to attacks on the inadequaciesof others, in particular the authors’ former close colleague donald johanson. here is a smallsampling:

in our years of collaboration at the institute he [johanson] developed a well-deserved, if unfortunate, reputation for unpredictable and high-decibel personalverbal assaults, sometimes accompanied by the tossing around of books orwhatever else came conveniently to hand.

so, bearing in mind that there is little you can say about human prehistory that won’t bedisputed by someone somewhere, other than that we most certainly had one, what we thinkwe know about who we are and where we come from is roughly this:

for the first 99.99999 percent of our history as organisms, we were in the same ancestralline as chimpanzees. virtually nothing is known about the prehistory of chimpanzees, butwhatever they were, we were. then about seven million years ago something major happened.

a group of new beings emerged from the tropical forests of africa and began to move abouton the open savanna.

these were the australopithecines, and for the next five million years they would be theworld’s dominant hominid species. (austral is from the latin for “southern” and has noconnection in this context to australia.) australopithecines came in several varieties, someslender and gracile, like raymond dart’s taung child, others more sturdy and robust, but allwere capable of walking upright. some of these species existed for well over a million years,others for a more modest few hundred thousand, but it is worth bearing in mind that even theleast successful had histories many times longer than we have yet achieved.

the most famous hominid remains in the world are those of a 3.18-million-year-oldaustralopithecine found at hadar in ethiopia in 1974 by a team led by donald johanson.

formally known as a.l. (for “afar locality”) 288–1, the skeleton became more familiarlyknown as lucy, after the beatles song “lucy in the sky with diamonds.” johanson has neverdoubted her importance. “she is our earliest ancestor, the missing link between ape andhuman,” he has said.

lucy was tiny—just three and a half feet tall. she could walk, though how well is a matterof some dispute. she was evidently a good climber, too. much else is unknown. her skull wasalmost entirely missing, so little could be said with confidence about her brain size, thoughskull fragments suggested it was small. most books describe lucy’s skeleton as being 40percent complete, though some put it closer to half, and one produced by the americanmuseum of natural history describes lucy as two-thirds complete. the bbc television series
ape man actually called it “a complete skeleton,” even while showing that it was anythingbut.

a human body has 206 bones, but many of these are repeated. if you have the left femurfrom a specimen, you don’t need the right to know its dimensions. strip out all the redundantbones, and the total you are left with is 120—what is called a half skeleton. even by this fairlyaccommodating standard, and even counting the slightest fragment as a full bone, lucyconstituted only 28 percent of a half skeleton (and only about 20 percent of a full one).

in the wisdom of the bones, alan walker recounts how he once asked johanson how hehad come up with a figure of 40 percent. johanson breezily replied that he had discounted the106 bones of the hands and feet—more than half the body’s total, and a fairly important half,too, one would have thought, since lucy’s principal defining attribute was the use of thosehands and feet to deal with a changing world. at all events, rather less is known about lucythan is generally supposed. it isn’t even actually known that she was a female. her sex ismerely presumed from her diminutive size.

two years after lucy’s discovery, at laetoli in tanzania mary leakey found footprints leftby two individuals from—it is thought—the same family of hominids. the prints had beenmade when two australopithecines had walked through muddy ash following a volcaniceruption. the ash had later hardened, preserving the impressions of their feet for a distance ofover twenty-three meters.

the american museum of natural history in new york has an absorbing diorama thatrecords the moment of their passing. it depicts life-sized re-creations of a male and a femalewalking side by side across the ancient african plain. they are hairy and chimplike indimensions, but have a bearing and gait that suggest humanness. the most striking feature ofthe display is that the male holds his left arm protectively around the female’s shoulder. it is atender and affecting gesture, suggestive of close bonding.

the tableau is done with such conviction that it is easy to overlook the consideration thatvirtually everything above the footprints is imaginary. almost every external aspect of thetwo figures—degree of hairiness, facial appendages (whether they had human noses or chimpnoses), expressions, skin color, size and shape of the female’s breasts—is necessarilysuppositional. we can’t even say that they were a couple. the female figure may in fact havebeen a child. nor can we be certain that they were australopithecines. they are assumed to beaustralopithecines because there are no other known candidates.

i had been told that they were posed like that because during the building of the dioramathe female figure kept toppling over, but ian tattersall insists with a laugh that the story isuntrue. “obviously we don’t know whether the male had his arm around the female or not,but we do know from the stride measurements that they were walking side by side and closetogether—close enough to be touching. it was quite an exposed area, so they were probablyfeeling vulnerable. that’s why we tried to give them slightly worried expressions.”

i asked him if he was troubled about the amount of license that was taken in reconstructingthe figures. “it’s always a problem in making re-creations,” he agreed readily enough. “youwouldn’t believe how much discussion can go into deciding details like whether neandertalshad eyebrows or not. it was just the same for the laetoli figures. we simply can’t know thedetails of what they looked like, but we can convey their size and posture and make somereasonable assumptions about their probable appearance. if i had it to do again, i think i might
have made them just slightly more apelike and less human. these creatures weren’t humans.

they were bipedal apes.”

until very recently it was assumed that we were descended from lucy and the laetolicreatures, but now many authorities aren’t so sure. although certain physical features (theteeth, for instance) suggest a possible link between us, other parts of the australopithecineanatomy are more troubling. in their book extinct humans, tattersall and schwartz point outthat the upper portion of the human femur is very like that of the apes but not of theaustralopithecines; so if lucy is in a direct line between apes and modern humans, it meanswe must have adopted an australopithecine femur for a million years or so, then gone back toan ape femur when we moved on to the next phase of our development. they believe, in fact,that not only was lucy not our ancestor, she wasn’t even much of a walker.

“lucy and her kind did not locomote in anything like the modern human fashion,” insiststattersall. “only when these hominids had to travel between arboreal habitats would they findthemselves walking bipedally, ‘forced’ to do so by their own anatomies.” johanson doesn’taccept this. “lucy’s hips and the muscular arrangement of her pelvis,” he has written, “wouldhave made it as hard for her to climb trees as it is for modern humans.”

matters grew murkier still in 2001 and 2002 when four exceptional new specimens werefound. one, discovered by meave leakey of the famous fossil-hunting family at laketurkana in kenya and called kenyanthropus platyops (“kenyan flat-face”), is from about thesame time as lucy and raises the possibility that it was our ancestor and lucy was anunsuccessful side branch. also found in 2001 were ardipithecus ramidus kadabba, dated atbetween 5.2 million and 5.8 million years old, and orrorin tugenensis, thought to be 6 millionyears old, making it the oldest hominid yet found—but only for a brief while. in the summerof 2002 a french team working in the djurab desert of chad (an area that had never beforeyielded ancient bones) found a hominid almost 7 million years old, which they labeledsahelanthropus tchadensis. (some critics believe that it was not human, but an early ape andtherefore should be called sahelpithecus.) all these were early creatures and quite primitivebut they walked upright, and they were doing so far earlier than previously thought.

bipedalism is a demanding and risky strategy. it means refashioning the pelvis into a fullload-bearing instrument. to preserve the required strength, the birth canal must becomparatively narrow. this has two very significant immediate consequences and one longer-term one. first, it means a lot of pain for any birthing mother and a greatly increased dangerof fatality to mother and baby both. moreover to get the baby’s head through such a tightspace it must be born while its brain is still small—and while the baby, therefore, is stillhelpless. this means long-term infant care, which in turn implies solid male–female bonding.

all this is problematic enough when you are the intellectual master of the planet, but whenyou are a small, vulnerable australopithecine, with a brain about the size of an orange,3therisk must have been enormous.

3absolute brain size does not tell you everything-or possibly sometimes even much. elephants and whales bothhave brains larger than ours, but you wouldnt have much trouble outwitting them in contract negotiations. it isrelative size that matters, a point that is often overlooked. as gould notes, a. africanus had a brain of only 450cubic centimeters, smaller than that of a gorilla. but a typical africanus male weighed less than a hundredpounds, and a female much less still, whereas gorillas can easily top out at 600 pounds (gould pp. 181-83).

so why did lucy and her kind come down from the trees and out of the forests? probablythey had no choice. the slow rise of the isthmus of panama had cut the flow of waters fromthe pacific into the atlantic, diverting warming currents away from the arctic and leading tothe onset of an exceedingly sharp ice age in northern latitudes. in africa, this would haveproduced seasonal drying and cooling, gradually turning jungle into savanna. “it was not somuch that lucy and her like left the forests,” john gribbin has written, “but that the forestsleft them.”

but stepping out onto the open savanna also clearly left the early hominids much moreexposed. an upright hominid could see better, but could also be seen better. even now as aspecies, we are almost preposterously vulnerable in the wild. nearly every large animal youcan care to name is stronger, faster, and toothier than us. faced with attack, modern humanshave only two advantages. we have a good brain, with which we can devise strategies, andwe have hands with which we can fling or brandish hurtful objects. we are the only creaturethat can harm at a distance. we can thus afford to be physically vulnerable.

all the elements would appear to have been in place for the rapid evolution of a potentbrain, and yet that seems not to have happened. for over three million years, lucy and herfellow australopithecines scarcely changed at all. their brain didn’t grow and there is no signthat they used even the simplest tools. what is stranger still is that we now know that forabout a million years they lived alongside other early hominids who did use tools, yet theaustralopithecines never took advantage of this useful technology that was all around them.

at one point between three and two million years ago, it appears there may have been asmany as six hominid types coexisting in africa. only one, however, was fated to last: homo,which emerged from the mists beginning about two million years ago. no one knows quitewhat the relationship was between australopithecines and homo, but what is known is thatthey coexisted for something over a million years before all the australopithecines, robust andgracile alike, vanished mysteriously, and possibly abruptly, over a million years ago. no oneknows why they disappeared. “perhaps,” suggests matt ridley, “we ate them.”

conventionally, the homo line begins with homo habilis, a creature about whom we knowalmost nothing, and concludes with us, homo sapiens (literally “man the thinker”). inbetween, and depending on which opinions you value, there have been half a dozen otherhomo species: homo ergaster, homo neanderthalensis, homo rudolfensis, homoheidelbergensis, homo erectus, and homo antecessor.

homo habilis (“handy man”) was named by louis leakey and colleagues in 1964 and wasso called because it was the first hominid to use tools, albeit very simple ones. it was a fairlyprimitive creature, much more chimpanzee than human, but its brain was about 50 percentlarger than that of lucy in gross terms and not much less large proportionally, so it was theeinstein of its day. no persuasive reason has ever been adduced for why hominid brainssuddenly began to grow two million years ago. for a long time it was assumed that big brainsand upright walking were directly related—that the movement out of the forests necessitatedcunning new strategies that fed off of or promoted braininess—so it was something of asurprise, after the repeated discoveries of so many bipedal dullards, to realize that there wasno apparent connection between them at all.

“there is simply no compelling reason we know of to explain why human brains gotlarge,” says tattersall. huge brains are demanding organs: they make up only 2 percent of thebody’s mass, but devour 20 percent of its energy. they are also comparatively picky in what
they use as fuel. if you never ate another morsel of fat, your brain would not complainbecause it won’t touch the stuff. it wants glucose instead, and lots of it, even if it means short-changing other organs. as guy brown notes: “the body is in constant danger of beingdepleted by a greedy brain, but cannot afford to let the brain go hungry as that would rapidlylead to death.” a big brain needs more food and more food means increased risk.

tattersall thinks the rise of a big brain may simply have been an evolutionary accident. hebelieves with stephen jay gould that if you replayed the tape of life—even if you ran it backonly a relatively short way to the dawn of hominids—the chances are “quite unlikely” thatmodern humans or anything like them would be here now.

“one of the hardest ideas for humans to accept,” he says, “is that we are not theculmination of anything. there is nothing inevitable about our being here. it is part of ourvanity as humans that we tend to think of evolution as a process that, in effect, wasprogrammed to produce us. even anthropologists tended to think this way right up until the1970s.” indeed, as recently as 1991, in the popular textbook the stages of evolution, c.

loring brace stuck doggedly to the linear concept, acknowledging just one evolutionary deadend, the robust australopithecines. everything else represented a straightforwardprogression—each species of hominid carrying the baton of development so far, then handingit on to a younger, fresher runner. now, however, it seems certain that many of these earlyforms followed side trails that didn’t come to anything.

luckily for us, one did—a group of tool users, which seemed to arise from out of nowhereand overlapped with the shadowy and much disputed homo habilis. this is homo erectus, thespecies discovered by eugène dubois in java in 1891. depending on which sources youconsult, it existed from about 1.8 million years ago to possibly as recently as twenty thousandor so years ago.

according to the java man authors, homo erectus is the dividing line: everything thatcame before him was apelike in character; everything that came after was humanlike. homoerectus was the first to hunt, the first to use fire, the first to fashion complex tools, the first toleave evidence of campsites, the first to look after the weak and frail. compared with all thathad gone before, homo erectus was extremely human in form as well as behavior, itsmembers long-limbed and lean, very strong (much stronger than modern humans), and withthe drive and intelligence to spread successfully over huge areas. to other hominids, homoerectus must have seemed terrifyingly powerful, fleet, and gifted.

erectus was “the velociraptor of its day,” according to alan walker of penn stateuniversity and one of the world’s leading authorities. if you were to look one in the eyes, itmight appear superficially to be human, but “you wouldn’t connect. you’d be prey.”

according to walker, it had the body of an adult human but the brain of a baby.

although erectus had been known about for almost a century it was known only fromscattered fragments—not enough to come even close to making one full skeleton. so it wasn’tuntil an extraordinary discovery in africa in the 1980s that its importance—or, at the veryleast, possible importance—as a precursor species for modern humans was fully appreciated.

the remote valley of lake turkana (formerly lake rudolf) in kenya is now one of theworld’s most productive sites for early human remains, but for a very long time no one hadthought to look there. it was only because richard leakey was on a flight that was divertedover the valley that he realized it might be more promising than had been thought. a teamwas dispatched to investigate, but at first found nothing. then late one afternoon kamoya
kimeu, leakey’s most renowned fossil hunter, found a small piece of hominid brow on a hillwell away from the lake. such a site was unlikely to yield much, but they dug anyway out ofrespect for kimeu’s instincts and to their astonishment found a nearly complete homo erectusskeleton. it was from a boy aged between about nine and twelve who had died 1.54 millionyears ago. the skeleton had “an entirely modern body structure,” says tattersall, in a way thatwas without precedent. the turkana boy was “very emphatically one of us.”

also found at lake turkana by kimeu was knm-er 1808, a female 1.7 million years old,which gave scientists their first clue that homo erectus was more interesting and complexthan previously thought. the woman’s bones were deformed and covered in coarse growths,the result of an agonizing condition called hypervitaminosis a, which can come only fromeating the liver of a carnivore. this told us first of all that homo erectus was eating meat.

even more surprising was that the amount of growth showed that she had lived weeks or evenmonths with the disease. someone had looked after her. it was the first sign of tenderness inhominid evolution.

it was also discovered that homo erectus skulls contained (or, in the view of some, possiblycontained) a broca’s area, a region of the frontal lobe of the brain associated with speech.

chimps don’t have such a feature. alan walker thinks the spinal canal didn’t have the sizeand complexity to enable speech, that they probably would have communicated about as wellas modern chimps. others, notably richard leakey, are convinced they could speak.

for a time, it appears, homo erectus was the only hominid species on earth. it was hugelyadventurous and spread across the globe with what seems to have been breathtaking rapidity.

the fossil evidence, if taken literally, suggests that some members of the species reached javaat about the same time as, or even slightly before, they left africa. this has led some hopefulscientists to suggest that perhaps modern people arose not in africa at all, but in asia—whichwould be remarkable, not to say miraculous, as no possible precursor species have ever beenfound anywhere outside africa. the asian hominids would have had to appear, as it were,spontaneously. and anyway an asian beginning would merely reverse the problem of theirspread; you would still have to explain how the java people then got to africa so quickly.

there are several more plausible alternative explanations for how homo erectus managedto turn up in asia so soon after its first appearance in africa. first, a lot of plus-or-minusinggoes into the dating of early human remains. if the actual age of the african bones is at thehigher end of the range of estimates or the javan ones at the lower end, or both, then there isplenty of time for african erects to find their way to asia. it is also entirely possible that oldererectus bones await discovery in africa. in addition, the javan dates could be wrongaltogether.

now for the doubts. some authorities don’t believe that the turkana finds are homoerectus at all. the snag, ironically, was that although the turkana skeletons were admirablyextensive, all othererectus fossils are inconclusively fragmentary. as tattersall and jeffreyschwartz note in extinct humans, most of the turkana skeleton “couldn’t be compared withanything else closely related to it because the comparable parts weren’t known!” the turkanaskeletons, they say, look nothing like any asian homo erectus and would never have beenconsidered the same species except that they were contemporaries. some authorities insist oncalling the turkana specimens (and any others from the same period) homo ergaster.

tattersall and schwartz don’t believe that goes nearly far enough. they believe it wasergaster“or a reasonably close relative” that spread to asia from africa, evolved intohomo erectus,and then died out.

what is certain is that sometime well over a million years ago, some new, comparativelymodern, upright beings left africa and boldly spread out across much of the globe. theypossibly did so quite rapidly, increasing their range by as much as twenty-five miles a year onaverage, all while dealing with mountain ranges, rivers, deserts, and other impediments andadapting to differences in climate and food sources. a particular mystery is how they passedalong the west side of the red sea, an area of famously punishing aridity now, but even drierin the past. it is a curious irony that the conditions that prompted them to leave africa wouldhave made it much more difficult to do so. yet somehow they managed to find their wayaround every barrier and to thrive in the lands beyond.

and that, i’m afraid, is where all agreement ends. what happened next in the history ofhuman development is a matter of long and rancorous debate, as we shall see in the nextchapter.

but it is worth remembering, before we move on, that all of these evolutionary jostlingsover five million years, from distant, puzzled australopithecine to fully modern human,produced a creature that is still 98.4 percent genetically indistinguishable from the modernchimpanzee. there is more difference between a zebra and a horse, or between a dolphin anda porpoise, than there is between you and the furry creatures your distant ancestors left behindwhen they set out to take over the world.

29    THE RESTLESS APESOME

time about a million and a half years ago, some forgotten genius of the hominidworld did an unexpected thing. he (or very possibly she) took one stone and carefully used itto shape another. the result was a simple teardrop-shaped hand axe, but it was the world’sfirst piece of advanced technology.

it was so superior to existing tools that soon others were following the inventor’s lead andmaking hand axes of their own. eventually whole societies existed that seemed to do littleelse. “they made them in the thousands,” says ian tattersall. “there are some places inafrica where you literally can’t move without stepping on them. it’s strange because they arequite intensive objects to make. it was as if they made them for the sheer pleasure of it.”

from a shelf in his sunny workroom tattersall took down an enormous cast, perhaps a footand a half long and eight inches wide at its widest point, and handed it to me. it was shapedlike a spearhead, but one the size of a stepping-stone. as a fiberglass cast it weighed only afew ounces, but the original, which was found in tanzania, weighed twenty-five pounds. “itwas completely useless as a tool,” tattersall said. “it would have taken two people to lift itadequately, and even then it would have been exhausting to try to pound anything with it.”

“what was it used for then?”

tattersall gave a genial shrug, pleased at the mystery of it. “no idea. it must have had somesymbolic importance, but we can only guess what.”

the axes became known as acheulean tools, after st. acheul, a suburb of amiens innorthern france, where the first examples were found in the nineteenth century, and contrastwith the older, simpler tools known as oldowan, originally found at olduvai gorge intanzania. in older textbooks, oldowan tools are usually shown as blunt, rounded, hand-sizedstones. in fact, paleoanthropologists now tend to believe that the tool part of oldowan rockswere the pieces flaked off these larger stones, which could then be used for cutting.

now here’s the mystery. when early modern humans—the ones who would eventuallybecome us—started to move out of africa something over a hundred thousand years ago,acheulean tools were the technology of choice. these early homo sapiens loved theiracheulean tools, too. they carried them vast distances. sometimes they even took unshapedrocks with them to make into tools later on. they were, in a word, devoted to the technology.

but although acheulean tools have been found throughout africa, europe, and western andcentral asia, they have almost never been found in the far east. this is deeply puzzling.

in the 1940s a harvard paleontologist named hallum movius drew something called themovius line, dividing the side with acheulean tools from the one without. the line runs in asoutheasterly direction across europe and the middle east to the vicinity of modern-daycalcutta and bangladesh. beyond the movius line, across the whole of southeast asia andinto china, only the older, simpler oldowan tools have been found. we know that homosapiens went far beyond this point, so why would they carry an advanced and treasured stonetechnology to the edge of the far east and then just abandon it?

“that troubled me for a long time,” recalls alan thorne of the australian nationaluniversity in canberra. “the whole of modern anthropology was built round the idea thathumans came out of africa in two waves—a first wave of homo erectus, which became javaman and peking man and the like, and a later, more advanced wave of homo sapiens, whichdisplaced the first lot. yet to accept that you must believe thathomo sapiens got so far withtheir more modern technology and then, for whatever reason, gave it up. it was all verypuzzling, to say the least.”

as it turned out, there would be a great deal else to be puzzled about, and one of the mostpuzzling findings of all would come from thorne’s own part of the world, in the outback ofaustralia. in 1968, a geologist named jim bowler was poking around on a long-dried lakebedcalled mungo in a parched and lonely corner of western new south wales when somethingvery unexpected caught his eye. sticking out of a crescent-shaped sand ridge of a type knownas a lunette were some human bones. at the time, it was believed that humans had been inaustralia for no more than 8,000 years, but mungo had been dry for 12,000 years. so whatwas anyone doing in such an inhospitable place?

the answer, provided by carbon dating, was that the bones’ owner had lived there whenlake mungo was a much more agreeable habitat, a dozen miles long, full of water and fish,fringed by pleasant groves of casuarina trees. to everyone’s astonishment, the bones turnedout to be 23,000 years old. other bones found nearby were dated to as much as 60,000 years.

this was unexpected to the point of seeming practically impossible. at no time sincehominids first arose on earth has australia not been an island. any human beings who arrivedthere must have come by sea, in large enough numbers to start a breeding population, aftercrossing sixty miles or more of open water without having any way of knowing that aconvenient landfall awaited them. having landed, the mungo people had then found their waymore than two thousand miles inland from australia’s north coast—the presumed point ofentry—which suggests, according to a report in the proceedings of the national academy ofsciences, “that people may have first arrived substantially earlier than 60,000 years ago.”

how they got there and why they came are questions that can’t be answered. according tomost anthropology texts, there’s no evidence that people could even speak 60,000 years ago,much less engage in the sorts of cooperative efforts necessary to build ocean-worthy craft andcolonize island continents.

“there’s just a whole lot we don’t know about the movements of people before recordedhistory,” alan thorne told me when i met him in canberra. “do you know that whennineteenth-century anthropologists first got to papua new guinea, they found people in thehighlands of the interior, in some of the most inaccessible terrain on earth, growing sweetpotatoes. sweet potatoes are native to south america. so how did they get to papua newguinea? we don’t know. don’t have the faintest idea. but what is certain is that people havebeen moving around with considerable assuredness for longer than traditionally thought, andalmost certainly sharing genes as well as information.”

the problem, as ever, is the fossil record. “very few parts of the world are even vaguelyamenable to the long-term preservation of human remains,” says thorne, a sharp-eyed manwith a white goatee and an intent but friendly manner. “if it weren’t for a few productiveareas like hadar and olduvai in east africa we’d know frighteningly little. and when youlook elsewhere, often wedo know frighteningly little. the whole of india has yielded just oneancient human fossil, from about 300,000 years ago. between iraq and vietnam—that’s adistance of some 5,000 kilometers—there have been just two: the one in india and aneandertal in uzbekistan.” he grinned. “that’s not a whole hell of a lot to work with. you’releft with the position that you’ve got a few productive areas for human fossils, like the greatrift valley in africa and mungo here in australia, and very little in between. it’s notsurprising that paleontologists have trouble connecting the dots.”

the traditional theory to explain human movements—and the one still accepted by themajority of people in the field—is that humans dispersed across eurasia in two waves. thefirst wave consisted of homo erectus, who left africa remarkably quickly—almost as soon asthey emerged as a species—beginning nearly two million years ago. over time, as they settledin different regions, these early erects further evolved into distinctive types—into java manand peking man in asia, and homo heidelbergensis and finally homo neanderthalensis ineurope.

then, something over a hundred thousand years ago, a smarter, lither species of creature—the ancestors of every one of us alive today—arose on the african plains and began radiatingoutward in a second wave. wherever they went, according to this theory, these new homosapiens displaced their duller, less adept predecessors. quite how they did this has alwaysbeen a matter of disputation. no signs of slaughter have ever been found, so most authoritiesbelieve the newer hominids simply outcompeted the older ones, though other factors may alsohave contributed. “perhaps we gave them smallpox,” suggests tattersall. “there’s no real wayof telling. the one certainty is that we are here now and they aren’t.”

these first modern humans are surprisingly shadowy. we know less about ourselves,curiously enough, than about almost any other line of hominids. it is odd indeed, as tattersallnotes, “that the most recent major event in human evolution—the emergence of our ownspecies—is perhaps the most obscure of all.” nobody can even quite agree where trulymodern humans first appear in the fossil record. many books place their debut at about120,000 years ago in the form of remains found at the klasies river mouth in south africa,but not everyone accepts that these were fully modern people. tattersall and schwartzmaintain that “whether any or all of them actually represent our species still awaits definitiveclarification.”

the first undisputed appearance of homo sapiens is in the eastern mediterranean, aroundmodern-day israel, where they begin to show up about 100,000 years ago—but even therethey are described (by trinkaus and shipman) as “odd, difficult-to-classify and poorlyknown.” neandertals were already well established in the region and had a type of tool kitknown as mousterian, which the modern humans evidently found worthy enough to borrow.

no neandertal remains have ever been found in north africa, but their tool kits turn up allover the place. somebody must have taken them there: modern humans are the onlycandidate. it is also known that neandertals and modern humans coexisted in some fashionfor tens of thousands of years in the middle east. “we don’t know if they time-shared thesame space or actually lived side by side,” tattersall says, but the moderns continued happilyto use neandertal tools—hardly convincing evidence of overwhelming superiority. no lesscuriously, acheulean tools are found in the middle east well over a million years ago, but
scarcely exist in europe until just 300,000 years ago. again, why people who had thetechnology didn’t take the tools with them is a mystery.

for a long time, it was believed that the cro-magnons, as modern humans in europebecame known, drove the neandertals before them as they advanced across the continent,eventually forcing them to its western margins, where essentially they had no choice but tofall in the sea or go extinct. in fact, it is now known that cro-magnons were in the far west ofeurope at about the same time they were also coming in from the east. “europe was a prettyempty place in those days,” tattersall says. “they may not have encountered each other allthat often, even with all their comings and goings.” one curiosity of the cro-magnons’ arrivalis that it came at a time known to paleoclimatology as the boutellier interval, when europewas plunging from a period of relative mildness into yet another long spell of punishing cold.

whatever it was that drew them to europe, it wasn’t the glorious weather.

in any case, the idea that neandertals crumpled in the face of competition from newlyarrived cro-magnons strains against the evidence at least a little. neandertals were nothing ifnot tough. for tens of thousands of years they lived through conditions that no modern humanoutside a few polar scientists and explorers has experienced. during the worst of the ice ages,blizzards with hurricane-force winds were common. temperatures routinely fell to 50 degreesbelow zero fahrenheit. polar bears padded across the snowy vales of southern england.

neandertals naturally retreated from the worst of it, but even so they will have experiencedweather that was at least as bad as a modern siberian winter. they suffered, to be sure—aneandertal who lived much past thirty was lucky indeed—but as a species they weremagnificently resilient and practically indestructible. they survived for at least a hundredthousand years, and perhaps twice that, over an area stretching from gibraltar to uzbekistan,which is a pretty successful run for any species of being.

quite who they were and what they were like remain matters of disagreement anduncertainty. right up until the middle of the twentieth century the accepted anthropologicalview of the neandertal was that he was dim, stooped, shuffling, and simian—thequintessential caveman. it was only a painful accident that prodded scientists to reconsiderthis view. in 1947, while doing fieldwork in the sahara, a franco-algerian paleontologistnamed camille arambourg took refuge from the midday sun under the wing of his lightairplane. as he sat there, a tire burst from the heat, and the plane tipped suddenly, striking hima painful blow on the upper body. later in paris he went for an x-ray of his neck, and noticedthat his own vertebrae were aligned exactly like those of the stooped and hulking neandertal.

either he was physiologically primitive or neandertal’s posture had been misdescribed. infact, it was the latter. neandertal vertebrae were not simian at all. it changed utterly how weviewed neandertals—but only some of the time, it appears.

it is still commonly held that neandertals lacked the intelligence or fiber to compete onequal terms with the continent’s slender and more cerebrally nimble newcomers, homosapiens. here is a typical comment from a recent book: “modern humans neutralized thisadvantage [the neandertal’s considerably heartier physique] with better clothing, better firesand better shelter; meanwhile the neandertals were stuck with an oversize body that requiredmore food to sustain.” in other words, the very factors that had allowed them to survivesuccessfully for a hundred thousand years suddenly became an insuperable handicap.

above all the issue that is almost never addressed is that neandertals had brains that weresignificantly larger than those of modern people—1.8 liters for neandertals versus 1.4 formodern people, according to one calculation. this is more than the difference between
modern homo sapiens and late homo erectus , a species we are happy to regard as barelyhuman. the argument put forward is that although our brains were smaller, they weresomehow more efficient. i believe i speak the truth when i observe that nowhere else inhuman evolution is such an argument made.

so why then, you may well ask, if the neandertals were so stout and adaptable andcerebrally well endowed, are they no longer with us? one possible (but much disputed)answer is that perhaps they are. alan thorne is one of the leading proponents of an alternativetheory, known as the multiregional hypothesis, which holds that human evolution has beencontinuous—that just as australopithecines evolved into homo habilis and homoheidelbergensis became over time homo neanderthalensis, so modernhomo sapiens simplyemerged from more ancient homo forms.homo erectus is, on this view, not a separate speciesbut just a transitional phase. thus modern chinese are descended from ancient homo erectusforebears in china, modern europeans from ancient european homo erectus, and so on.

“except that for me there are no homo erectus,” says thorne. “i think it’s a term which hasoutlived its usefulness. for me, homo erectus is simply an earlier part of us. i believe onlyone species of humans has ever left africa, and that species ishomo sapiens.”

opponents of the multiregional theory reject it, in the first instance, on the grounds that itrequires an improbable amount of parallel evolution by hominids throughout the old world—in africa, china, europe, the most distant islands of indonesia, wherever they appeared. somealso believe that multiregionalism encourages a racist view that anthropology took a very longtime to rid itself of. in the early 1960s, a famous anthropologist named carleton coon of theuniversity of pennsylvania suggested that some modern races have different sources oforigin, implying that some of us come from more superior stock than others. this hearkenedback uncomfortably to earlier beliefs that some modern races such as the african “bushmen”

(properly the kalahari san) and australian aborigines were more primitive than others.

whatever coon may personally have felt, the implication for many people was that someraces are inherently more advanced, and that some humans could essentially constitutedifferent species. the view, so instinctively offensive now, was widely popularized in manyrespectable places until fairly recent times. i have before me a popular book published bytime-life publications in 1961 called the epic of man based on a series of articles in lifemagazine. in it you can find such comments as “rhodesian man . . . lived as recently as25,000 years ago and may have been an ancestor of the african negroes. his brain size wasclose to that of homo sapiens.” in other words black africans were recently descended fromcreatures that were only “close” to homo sapiens.

thorne emphatically (and i believe sincerely) dismisses the idea that his theory is in anymeasure racist and accounts for the uniformity of human evolution by suggesting that therewas a lot of movement back and forth between cultures and regions. “there’s no reason tosuppose that people only went in one direction,” he says. “people were moving all over theplace, and where they met they almost certainly shared genetic material throughinterbreeding. new arrivals didn’t replace the indigenous populations, they joined them. theybecame them.” he likens the situation to when explorers like cook or magellan encounteredremote peoples for the first time. “they weren’t meetings of different species, but of the samespecies with some physical differences.”

what you actually see in the fossil record, thorne insists, is a smooth, continuoustransition. “there’s a famous skull from petralona in greece, dating from about 300,000 yearsago, that has been a matter of contention among traditionalists because it seems in some ways
homo erectus but in other ways homo sapiens. well, what we say is that this is just what youwould expect to find in species that were evolving rather than being displaced.”

one thing that would help to resolve matters would be evidence of interbreeding, but that isnot at all easy to prove, or disprove, from fossils. in 1999, archeologists in portugal found theskeleton of a child about four years old that died 24,500 years ago. the skeleton was modernoverall, but with certain archaic, possibly neandertal, characteristics: unusually sturdy legbones, teeth bearing a distinctive “shoveling” pattern, and (though not everyone agrees on it)an indentation at the back of the skull called a suprainiac fossa, a feature exclusive toneandertals. erik trinkaus of washington university in st. louis, the leading authority onneandertals, announced the child to be a hybrid: proof that modern humans and neandertalsinterbred. others, however, were troubled that the neandertal and modern features weren’tmore blended. as one critic put it: “if you look at a mule, you don’t have the front endlooking like a donkey and the back end looking like a horse.”

ian tattersall declared it to be nothing more than “a chunky modern child.” he accepts thatthere may well have been some “hanky-panky” between neandertals and moderns, butdoesn’t believe it could have resulted in reproductively successful offspring.

1“i don’t knowof any two organisms from any realm of biology that are that different and still in the samespecies,” he says.

with the fossil record so unhelpful, scientists have turned increasingly to genetic studies,in particular the part known as mitochondrial dna. mitochondrial dna was only discoveredin 1964, but by the 1980s some ingenious souls at the university of california at berkeley hadrealized that it has two features that lend it a particular convenience as a kind of molecularclock: it is passed on only through the female line, so it doesn’t become scrambled withpaternal dna with each new generation, and it mutates about twenty times faster than normalnuclear dna, making it easier to detect and follow genetic patterns over time. by tracking therates of mutation they could work out the genetic history and relationships of whole groups ofpeople.

in 1987, the berkeley team, led by the late allan wilson, did an analysis of mitochondrialdna from 147 individuals and declared that the rise of anatomically modern humansoccurred in africa within the last 140,000 years and that “all present-day humans aredescended from that population.” it was a serious blow to the multiregionalists. but thenpeople began to look a little more closely at the data. one of the most extraordinary points—almost too extraordinary to credit really—was that the “africans” used in the study wereactually african-americans, whose genes had obviously been subjected to considerablemediation in the past few hundred years. doubts also soon emerged about the assumed ratesof mutations.

by 1992, the study was largely discredited. but the techniques of genetic analysiscontinued to be refined, and in 1997 scientists from the university of munich managed toextract and analyze some dna from the arm bone of the original neandertal man, and thistime the evidence stood up. the munich study found that the neandertal dna was unlike anydna found on earth now, strongly indicating that there was no genetic connection betweenneandertals and modern humans. now this really was a blow to multiregionalism.

1one possibility is that neandertals and cro-magnons had different numbers of chromosomes, a complicationthat commonly arises when species that are close but not quite identical conjoin. in the equine world, forexample, horses have 64 chromosomes and donkeys 62. mate the two and you get an offspring with areproductively useless number of chromosomes, 63. you have, in short, a sterile mule.

then in late 2000 nature and other publications reported on a swedish study of themitochondrial dna of fifty-three people, which suggested that all modern humans emergedfrom africa within the past 100,000 years and came from a breeding stock of no more than10,000 individuals. soon afterward, eric lander, director of the whiteheadinstitute/massachusetts institute of technology center for genome research, announced thatmodern europeans, and perhaps people farther afield, are descended from “no more than afew hundred africans who left their homeland as recently as 25,000 years ago.”

as we have noted elsewhere in the book, modern human beings show remarkably littlegenetic variability—“there’s more diversity in one social group of fifty-five chimps than inthe entire human population,” as one authority has put it—and this would explain why.

because we are recently descended from a small founding population, there hasn’t been timeenough or people enough to provide a source of great variability. it seemed a pretty severeblow to multiregionalism. “after this,” a penn state academic told the washington post,“people won’t be too concerned about the multiregional theory, which has very littleevidence.”

but all of this overlooked the more or less infinite capacity for surprise offered by theancient mungo people of western new south wales. in early 2001, thorne and his colleaguesat the australian national university reported that they had recovered dna from the oldest ofthe mungo specimens—now dated at 62,000 years—and that this dna proved to be“genetically distinct.”

the mungo man, according to these findings, was anatomically modern—just like you andme—but carried an extinct genetic lineage. his mitochondrial dna is no longer found inliving humans, as it should be if, like all other modern people, he was descended from peoplewho left africa in the recent past.

“it turned everything upside down again,” says thorne with undisguised delight.

then other even more curious anomalies began to turn up. rosalind harding, a populationgeneticist at the institute of biological anthropology in oxford, while studying betaglobingenes in modern people, found two variants that are common among asians and theindigenous people of australia, but hardly exist in africa. the variant genes, she is certain,arose more than 200,000 years ago not in africa, but in east asia—long before modern homosapiens reached the region. the only way to account for them is to say that ancestors ofpeople now living in asia included archaic hominids—java man and the like. interestingly,this same variant gene—the java man gene, so to speak—turns up in modern populations inoxfordshire.

confused, i went to see harding at the institute, which inhabits an old brick villa onbanbury road in oxford, in more or less the neighborhood where bill clinton spent hisstudent days. harding is a small and chirpy australian, from brisbane originally, with the rareknack for being amused and earnest at the same time.

“don’t know,” she said at once, grinning, when i asked her how people in oxfordshireharbored sequences of betaglobin that shouldn’t be there. “on the whole,” she went on moresomberly, “the genetic record supports the out-of-africa hypothesis. but then you find theseanomalous clusters, which most geneticists prefer not to talk about. there’s huge amounts ofinformation that would be available to us if only we could understand it, but we don’t yet.

we’ve barely begun.” she refused to be drawn out on what the existence of asian-origin
genes in oxfordshire tells us other than that the situation is clearly complicated. “all we cansay at this stage is that it is very untidy and we don’t really know why.”

at the time of our meeting, in early 2002, another oxford scientist named bryan sykes hadjust produced a popular book called the seven daughters of eve in which, using studies ofmitochondrial dna, he had claimed to be able to trace nearly all living europeans back to afounding population of just seven women—the daughters of eve of the title—who livedbetween 10,000 and 45,000 years ago in the time known to science as the paleolithic. to eachof these women sykes had given a name—ursula, xenia, jasmine, and so on—and even adetailed personal history. (“ursula was her mother’s second child. the first had been taken bya leopard when he was only two. . . .”)when i asked harding about the book, she smiled broadly but carefully, as if not quitecertain where to go with her answer. “well, i suppose you must give him some credit forhelping to popularize a difficult subject,” she said and paused thoughtfully. “and thereremains the remote possibility that he’s right.” she laughed, then went on more intently:

“data from any single gene cannot really tell you anything so definitive. if you follow themitochondrial dna backwards, it will take you to a certain place—to an ursula or tara orwhatever. but if you take any other bit of dna, any gene at all, and traceit back, it will takeyou someplace else altogether.”

it was a little, i gathered, like following a road randomly out of london and finding thateventually it ends at john o’groats, and concluding from this that anyone in london musttherefore have come from the north of scotland. they might have come from there, of course,but equally they could have arrived from any of hundreds of other places. in this sense,according to harding, every gene is a different highway, and we have only barely begun tomap the routes. “no single gene is ever going to tell you the whole story,” she said.

so genetic studies aren’t to be trusted?

“oh you can trust the studies well enough, generally speaking. what you can’t trust are thesweeping conclusions that people often attach to them.”

she thinks out-of-africa is “probably 95 percent correct,” but adds: “i think both sides havedone a bit of a disservice to science by insisting that it must be one thing or the other. thingsare likely to turn out to be not so straightforward as either camp would have you believe. theevidence is clearly starting to suggest that there were multiple migrations and dispersals indifferent parts of the world going in all kinds of directions and generally mixing up the genepool. that’s never going to be easy to sort out.”

just at this time, there were also a number of reports questioning the reliability of claimsconcerning the recovery of very ancient dna. an academic writing in nature had noted howa paleontologist, asked by a colleague whether he thought an old skull was varnished or not,had licked its top and announced that it was. “in the process,” noted the nature article, “largeamounts of modern human dna would have been transferred to the skull,” rendering ituseless for future study. i asked harding about this. “oh, it would almost certainly have beencontaminated already,” she said. “just handling a bone will contaminate it. breathing on itwill contaminate it. most of the water in our labs will contaminate it. we are all swimming inforeign dna. in order to get a reliably clean specimen you have to excavate it in sterileconditions and do the tests on it at the site. it is the trickiest thing in the world not tocontaminate a specimen.”

so should such claims be treated dubiously? i asked.

harding nodded solemnly. “very,” she said.

if you wish to understand at once why we know as little as we do about human origins, ihave the place for you. it is to be found a little beyond the edge of the blue ngong hills inkenya, to the south and west of nairobi. drive out of the city on the main highway touganda, and there comes a moment of startling glory when the ground falls away and you arepresented with a hang glider’s view of boundless, pale green african plain.

this is the great rift valley, which arcs across three thousand miles of east africa,marking the tectonic rupture that is setting africa adrift from asia. here, perhaps forty milesout of nairobi, along the baking valley floor, is an ancient site called olorgesailie, which oncestood beside a large and pleasant lake. in 1919, long after the lake had vanished, a geologistnamed j. w. gregory was scouting the area for mineral prospects when he came across astretch of open ground littered with anomalous dark stones that had clearly been shaped byhuman hand. he had found one of the great sites of acheulean tool manufacture that iantattersall had told me about.

unexpectedly in the autumn of 2002 i found myself a visitor to this extraordinary site. iwas in kenya for another purpose altogether, visiting some projects run by the charity careinternational, but my hosts, knowing of my interest in humans for the present volume, hadinserted a visit to olorgesailie into the schedule.

after its discovery by gregory, olorgesailie lay undisturbed for over two decades beforethe famed husband-and-wife team of louis and mary leakey began an excavation that isn’tcompleted yet. what the leakeys found was a site stretching to ten acres or so, where toolswere made in incalculable numbers for roughly a million years, from about 1.2 million yearsago to 200,000 years ago. today the tool beds are sheltered from the worst of the elementsbeneath large tin lean-tos and fenced off with chicken wire to discourage opportunisticscavenging by visitors, but otherwise the tools are left just where their creators dropped themand where the leakeys found them.

jillani ngalli, a keen young man from the kenyan national museum who had beendispatched to act as guide, told me that the quartz and obsidian rocks from which the axeswere made were never found on the valley floor. “they had to carry the stones from there,” hesaid, nodding at a pair of mountains in the hazy middle distance, in opposite directions fromthe site: olorgesailie and ol esakut. each was about ten kilometers, or six miles, away—along way to carry an armload of stone.

why the early olorgesailie people went to such trouble we can only guess, of course. notonly did they lug hefty stones considerable distances to the lakeside, but, perhaps even moreremarkably, they then organized the site. the leakeys’ excavations revealed that there wereareas where axes were fashioned and others where blunt axes were brought to be resharpened.

olorgesailie was, in short, a kind of factory; one that stayed in business for a million years.

various replications have shown that the axes were tricky and labor-intensive objects tomake—even with practice, an axe would take hours to fashion—and yet, curiously, they werenot particularly good for cutting or chopping or scraping or any of the other tasks to whichthey were presumably put. so we are left with the position that for a million years—far, farlonger than our own species has even been in existence, much less engaged in continuous
cooperative efforts—early people came in considerable numbers to this particular site to makeextravagantly large numbers of tools that appear to have been rather curiously pointless.

and who were these people? we have no idea actually. we assume they were homoerectus because there are no other known candidates, which means that at their peak—theirpeak —the olorgesailie workers would have had the brains of a modern infant. but there is nophysical evidence on which to base a conclusion. despite over sixty years of searching, nohuman bone has ever been found in or around the vicinity of olorgesailie. however muchtime they spent there shaping rocks, it appears they went elsewhere to die.

“it’s all a mystery,” jillani ngalli told me, beaming happily.

the olorgesailie people disappeared from the scene about 200,000 years ago when the lakedried up and the rift valley started to become the hot and challenging place it is today. butby this time their days as a species were already numbered. the world was about to get itsfirst real master race, homo sapiens . things would never be the same again.

Goodbye

in the early 1680s, at just about the time that edmond halley and his friends christopherwren and robert hooke were settling down in a london coffeehouse and embarking on thecasual wager that would result eventually in isaac newton’s principia , henry cavendish’sweighing of the earth, and many of the other inspired and commendable undertakings thathave occupied us for much of the past four hundred pages, a rather less desirable milestonewas being passed on the island of mauritius, far out in the indian ocean some eight hundredmiles off the east coast of madagascar.

there, some forgotten sailor or sailor’s pet was harrying to death the last of the dodos, thefamously flightless bird whose dim but trusting nature and lack of leggy zip made it a ratherirresistible target for bored young tars on shore leave. millions of years of peaceful isolationhad not prepared it for the erratic and deeply unnerving behavior of human beings.

we don’t know precisely the circumstances, or even year, attending the last moments of thelast dodo, so we don’t know which arrived first, a world that contained a principia or one thathad no dodos, but we do know that they happened at more or less the same time. you wouldbe hard pressed, i would submit, to find a better pairing of occurrences to illustrate the divineand felonious nature of the human being—a species of organism that is capable of unpickingthe deepest secrets of the heavens while at the same time pounding into extinction, for nopurpose at all, a creature that never did us any harm and wasn’t even remotely capable ofunderstanding what we were doing to it as we did it. indeed, dodos were so spectacularlyshort on insight, it is reported, that if you wished to find all the dodos in a vicinity you hadonly to catch one and set it to squawking, and all the others would waddle along to see whatwas up.

the indignities to the poor dodo didn’t end quite there. in 1755, some seventy years afterthe last dodo’s death, the director of the ashmolean museum in oxford decided that theinstitution’s stuffed dodo was becoming unpleasantly musty and ordered it tossed on abonfire. this was a surprising decision as it was by this time the only dodo in existence,stuffed or otherwise. a passing employee, aghast, tried to rescue the bird but could save onlyits head and part of one limb.

as a result of this and other departures from common sense, we are not now entirely surewhat a living dodo was like. we possess much less information than most people suppose—ahandful of crude descriptions by “unscientific voyagers, three or four oil paintings, and a fewscattered osseous fragments,” in the somewhat aggrieved words of the nineteenth-centurynaturalist h. e. strickland. as strickland wistfully observed, we have more physical evidenceof some ancient sea monsters and lumbering saurapods than we do of a bird that lived intomodern times and required nothing of us to survive except our absence.

so what is known of the dodo is this: it lived on mauritius, was plump but not tasty, andwas the biggest-ever member of the pigeon family, though by quite what margin is unknownas its weight was never accurately recorded. extrapolations from strickland’s “osseous fragments” and the ashmolean’s modest remains show that it was a little over two and a halffeet tall and about the same distance from beak tip to backside. being flightless, it nested onthe ground, leaving its eggs and chicks tragically easy prey for pigs, dogs, and monkeysbrought to the island by outsiders. it was probably extinct by 1683 and was most certainlygone by 1693. beyond that we know almost nothing except of course that we will not see itslike again. we know nothing of its reproductive habits and diet, where it ranged, what soundsit made in tranquility or alarm. we don’t possess a single dodo egg.

from beginning to end our acquaintance with animate dodos lasted just seventy years. thatis a breathtakingly scanty period—though it must be said that by this point in our history wedid have thousands of years of practice behind us in the matter of irreversible eliminations.

nobody knows quite how destructive human beings are, but it is a fact that over the last fiftythousand years or so wherever we have gone animals have tended to vanish, in oftenastonishingly large numbers.

in  America,  thirty  genera  of  large  animals—some very large indeed—disappearedpractically at a stroke after the arrival of modern humans on the continent between ten andtwenty thousand years ago. altogether north and south america between them lost aboutthree quarters of their big animals once man the hunter arrived with his flint-headed spearsand keen organizational capabilities. europe and asia, where the animals had had longer toevolve a useful wariness of humans, lost between a third and a half of their big creatures.

Australia, for exactly the opposite reasons, lost no less than 95 percent.

because the early hunter populations were comparatively small and the animal populationstruly monumental—as many as ten million mammoth carcasses are thought to lie frozen in thetundra of northern siberia alone—some authorities think there must be other explanations,possibly involving climate change or some kind of pandemic. as ross macphee of theamerican museum of natural history put it: “there’s no material benefit to huntingdangerous animals more often than you need to—there are only so many mammoth steaksyou can eat.” others believe it may have been almost criminally easy to catch and clobberprey. “in australia and the americas,” says tim flannery, “the animals probably didn’t knowenough to run away.”

some of the creatures that were lost were singularly spectacular and would take a littlemanaging if they were still around. imagine ground sloths that could look into an upstairswindow, tortoises nearly the size of a small fiat, monitor lizards twenty feet long baskingbeside desert highways in western australia. alas, they are gone and we live on a muchdiminished planet. today, across the whole world, only four types of really hefty (a metric tonor more) land animals survive: elephants, rhinos, hippos, and giraffes. not for tens of millionsof years has life on earth been so diminutive and tame.

the question that arises is whether the disappearances of the stone age and disappearancesof more recent times are in effect part of a single extinction event—whether, in short, humansare inherently bad news for other living things. the sad likelihood is that we may well be.

according to the university of chicago paleontologist david raup, the background rate ofextinction on earth throughout biological history has been one species lost every four yearson average. according to one recent calculation, human-caused extinction now may berunning as much as 120,000 times that level.

in the mid-1990s, the australian naturalist tim flannery, now head of the south australianmuseum in adelaide, became struck by how little we seemed to know about many
extinctions, including relatively recent ones. “wherever you looked, there seemed to be gapsin the records—pieces missing, as with the dodo, or not recorded at all,” he told me when imet him in melbourne a year or so ago.

flannery recruited his friend peter schouten, an artist and fellow australian, and togetherthey embarked on a slightly obsessive quest to scour the world’s major collections to find outwhat was lost, what was left, and what had never been known at all. they spent four yearspicking through old skins, musty specimens, old drawings, and written descriptions—whatever was available. schouten made life-sized paintings of every animal they couldreasonably re-create, and flannery wrote the words. the result was an extraordinary bookcalled a gap in nature, constituting the most complete—and, it must be said, moving—catalog of animal extinctions from the last three hundred years.

for some animals, records were good, but nobody had done anything much with them,sometimes for years, sometimes forever. steller’s sea cow, a walrus-like creature related tothe dugong, was one of the last really big animals to go extinct. it was truly enormous—anadult could reach lengths of nearly thirty feet and weigh ten tons—but we are acquainted withit only because in 1741 a russian expedition happened to be shipwrecked on the only placewhere the creatures still survived in any numbers, the remote and foggy commander islandsin the bering sea.

happily, the expedition had a naturalist, georg steller, who was fascinated by the animal.

“he took the most copious notes,” says flannery. “he even measured the diameter of itswhiskers. the only thing he wouldn’t describe was the male genitals—though, for somereason, he was happy enough to do the female’s. he even saved a piece of skin, so we had agood idea of its texture. we weren’t always so lucky.”

the one thing steller couldn’t do was save the sea cow itself. already hunted to the brinkof extinction, it would be gone altogether within twenty-seven years of steller’s discovery ofit. many other animals, however, couldn’t be included because too little is known about them.

the darling downs hopping mouse, chatham islands swan, ascension island flightless crake,at least five types of large turtle, and many others are forever lost to us except as names.

a great deal of extinction, flannery and schouten discovered, hasn’t been cruel or wanton,but just kind of majestically foolish. in 1894, when a lighthouse was built on a lonely rockcalled stephens island, in the tempestuous strait between the north and south islands of newzealand, the lighthouse keeper’s cat kept bringing him strange little birds that it had caught.

the keeper dutifully sent some specimens to the museum in wellington. there a curator grewvery excited because the bird was a relic species of flightless wrens—the only example of aflightless perching bird ever found anywhere. he set off at once for the island, but by the timehe got there the cat had killed them all. twelve stuffed museum species of the stephens islandflightless wren are all that now exist.

at least we have those. all too often, it turns out, we are not much better at looking afterspecies after they have gone than we were before they went. take the case of the lovelycarolina parakeet. emerald green, with a golden head, it was arguably the most striking andbeautiful bird ever to live in north america—parrots don’t usually venture so far north, asyou may have noticed—and at its peak it existed in vast numbers, exceeded only by thepassenger pigeon. but the carolina parakeet was also considered a pest by farmers and easilyhunted because it flocked tightly and had a peculiar habit of flying up at the sound of gunfire(as you would expect), but then returning almost at once to check on fallen comrades.

in his classic american omithology, written in the early nineteenth century, charleswillson peale describes an occasion in which he repeatedly empties a shotgun into a tree inwhich they roost:

at each successive discharge, though showers of them fell, yet the affection of thesurvivors seemed rather to increase; for, after a few circuits around the place, they againalighted near me, looking down on their slaughtered companions with such manifestsymptoms of sympathy and concern, as entirely disarmed me.

by the second decade of the twentieth century, the birds had been so relentlessly huntedthat only a few remained alive in captivity. the last one, named inca, died in the cincinnatizoo in 1918 (not quite four years after the last passenger pigeon died in the same zoo) andwas reverently stuffed. and where would you go to see poor inca now? nobody knows. thezoo lost it.

what is both most intriguing and puzzling about the story above is that peale was a lover ofbirds, and yet did not hesitate to kill them in large numbers for no better reason than that itinterested him to do so. it is a truly astounding fact that for the longest time the people whowere most intensely interested in the world’s living things were the ones most likely toextinguish them.

no one represented this position on a larger scale (in every sense) than lionel walterrothschild, the second baron rothschild. scion of the great banking family, rothschild was astrange and reclusive fellow. he lived his entire life in the nursery wing of his home at tring,in buckinghamshire, using the furniture of his childhood—even sleeping in his childhoodbed, though eventually he weighed three hundred pounds.

his passion was natural history and he became a devoted accumulator of objects. he senthordes of trained men—as many as four hundred at a time—to every quarter of the globe toclamber over mountains and hack their way through jungles in the pursuit of newspecimens—particularly things that flew. these were crated or boxed up and sent back torothschild’s estate at tring, where he and a battalion of assistants exhaustively logged andanalyzed everything that came before them, producing a constant stream of books, papers, andmonographs—some twelve hundred in all. altogether, rothschild’s natural history factoryprocessed well over two million specimens and added five thousand species of creature to thescientific archive.

remarkably, rothschild’s collecting efforts were neither the most extensive nor the mostgenerously funded of the nineteenth century. that title almost certainly belongs to a slightlyearlier but also very wealthy british collector named hugh cuming, who became sopreoccupied with accumulating objects that he built a large oceangoing ship and employed acrew to sail the world full-time, picking up whatever they could find—birds, plants, animalsof all types, and especially shells. it was his unrivaled collection of barnacles that passed todarwin and served as the basis for his seminal study.

however, rothschild was easily the most scientific collector of his age, though also themost regrettably lethal, for in the 1890s he became interested in hawaii, perhaps the mosttemptingly vulnerable environment earth has yet produced. millions of years of isolation hadallowed hawaii to evolve 8,800 unique species of animals and plants. of particular interest torothschild were the islands’ colorful and distinctive birds, often consisting of very smallpopulations inhabiting extremely specific ranges.

the tragedy for many hawaiian birds was that they were not only distinctive, desirable, andrare—a dangerous combination in the best of circumstances—but also often heartbreakinglyeasy to take. the greater koa finch, an innocuous member of the honeycreeper family, lurkedshyly in the canopies of koa trees, but if someone imitated its song it would abandon its coverat once and fly down in a show of welcome. the last of the species vanished in 1896, killedby rothschild’s ace collector harry palmer, five years after the disappearance of its cousin thelesser koa finch, a bird so sublimely rare that only one has ever been seen: the one shot forrothschild’s collection. altogether during the decade or so of rothschild’s most intensivecollecting, at least nine species of hawaiian birds vanished, but it may have been more.

Rothschild was by no means alone in his zeal to capture birds at more or less any cost.

others in fact were more ruthless. in 1907 when a well-known collector named alansonbryan realized that he had shot the last three specimens of black mamos, a species of forestbird that had only been discovered the previous decade, he noted that the news filled him with“joy.”

it was, in short, a difficult age to fathom—a time when almost any animal was persecuted ifit was deemed the least bit intrusive. in 1890, new york state paid out over one hundredbounties for eastern mountain lions even though it was clear that the much-harassed creatureswere on the brink of extinction. right up until the 1940s many states continued to paybounties for almost any kind of predatory creature. west virginia gave out an annual collegescholarship to whoever brought in the most dead pests—and “pests” was liberally interpretedto mean almost anything that wasn’t grown on farms or kept as pets.

perhaps nothing speaks more vividly for the strangeness of the times than the fate of thelovely little bachman’s warbler. a native of the southern united states, the warbler wasfamous for its unusually thrilling song, but its population numbers, never robust, graduallydwindled until by the 1930s the warbler vanished altogether and went unseen for many years.

then in 1939, by happy coincidence two separate birding enthusiasts, in widely separatedlocations, came across lone survivors just two days apart. they both shot the birds, and thatwas the last that was ever seen of bachman’s warblers.

the impulse to exterminate was by no means exclusively american. in australia, bountieswere paid on the tasmanian tiger (properly the thylacine), a doglike creature with distinctive“tiger” stripes across its back, until shortly before the last one died, forlorn and nameless, in aprivate hobart zoo in 1936. go to the tasmanian museum today and ask to see the last of thisspecies—the only large carnivorous marsupial to live into modern times—and all they canshow you are photographs. the last surviving thylacine was thrown out with the weekly trash.

i mention all this to make the point that if you were designing an organism to look after lifein our lonely cosmos, to monitor where it is going and keep a record of where it has been, you wouldn’t choose human beings for the job.

but here’s an extremely salient point: we have been chosen, by fate or providence orwhatever you wish to call it. as far as we can tell, we are the best there is. we may be allthere is. it’s an unnerving thought that we may be the living universe’s supreme achievementand its worst nightmare simultaneously.

because we are so remarkably careless about looking after things, both when alive andwhen not, we have no idea—really none at all—about how many things have died offpermanently, or may soon, or may never, and what role we have played in any part of theprocess. in 1979, in the book the sinking ark, the author norman myers suggested thathuman activities were causing about two extinctions a week on the planet. by the early 1990she had raised the figure to some six hundred per week. (that’s extinctions of all types—plants, insects, and so on as well as animals.) others have put the figure even higher—to wellover a thousand a week. a united nations report of 1995, on the other hand, put the totalnumber of known extinctions in the last four hundred years at slightly under 500 for animalsand slightly over 650 for plants—while allowing that this was “almost certainly anunderestimate,” particularly with regard to tropical species. a few interpreters think mostextinction figures are grossly inflated.

the fact is, we don’t know. don’t have any idea. we don’t know when we started doingmany of the things we’ve done. we don’t know what we are doing right now or how ourpresent actions will affect the future. what we do know is that there is only one planet to do iton, and only one species of being capable of making a considered difference. Edward o.Wilson expressed it with unimprovable brevity in the diversity of life: “one planet, on eexperiment.”

if this book has a lesson, it is that we are awfully lucky to be here—and by “we” i meanevery living thing. to attain any kind of life in this universe of ours appears to be quite anachievement. as humans we are doubly lucky, of course: we enjoy not only the privilege ofexistence but also the singular ability to appreciate it and even, in a multitude of ways, tomake it better. it is a talent we have only barely begun to grasp.

we have arrived at this position of eminence in a stunningly short time. behaviorallymodern human beings—that is, people who can speak and make art and organize complexactivities—have existed for only about 0.0001 percent of earth’s history. but surviving foreven that little while has required a nearly endless string of good fortune.

we really are at the beginning of it all. the trick, of course, is to make sure we never findthe end. and that, almost certainly, will require a good deal more than lucky breaks.

ACKNOWLEDGMENTS

as i sit here, in early 2003, i have before me several pages of manuscript bearing majestically encouraging and tactful notes from ian tattersal of the american museum of natural history pointing out, inter alia, that perigueux is not a wine producing region, that it is inventive but atouch unorthodox of me to italicize taxonomic divisions above the level of genus and species,that i have persistently misspelled olorgesaille, a place that i recently visited, and so on in similar vein through two chapters of text covering his area of expertise, early humans.

goodness knows how many other inky embarrassments may lurk in these pages yet, but itis thanks to dr. tattersall and all of those whom i am about to mention that there arent manyhundreds more. i cannot begin to thank adequately those who helped me in the preparation ofthis book. i am especially indebted to the following, who were uniformly generous and kindlyand showed the most heroic reserves of patience in answering one simple, endlessly repeatedquestion: “im sorry, but can you explain that again?”in the united states: ian tattersall of the american museum of natural history in newyork; john thorstensen, mary k. hudson, and david blanchflower of dartmouth college inhanover, new hampshire; dr. william abdu and dr. bryan marsh of dartmouth-hitchcockmedical center in lebanon, new hampshire; ray anderson and brian witzke of the iowadepartment of natural resources, iowa city; mike voorhies of the university of nebraskaand ashfall fossil beds state park near orchard, nebraska; chuck offenburger of buenavista university, storm lake, iowa; ken rancourt, director of research, mount washingtonobservatory, gorham, new hampshire; paul doss, geologist of yellowstone national park,and his wife, heidi, also of the national park; frank asara of the university of california atberkeley; oliver payne and lynn addison of the national geographic society; james o.

farlow, indianapurdue university; roger l. larson, professor of marine geophysics,university of rhode island; jeff guinn of the fort worth star-telegram newspaper; jerry kasten of dallas, texas; and the staff of the iowa historical society in desmoines.

in england: david caplin of imperial college, london; richard fortey, les ellis, and kathyway of the natural history museum; martin raff of university college, london; rosalindharding of the institute of biological anthropology in oxford; dr. laurence smaje, formerlyof the wellcome institute; and keith blackmore of  the times.

in australia: the reverend robert evans of hazelbrook, new south wales; alan thorneand victoria bennett of the australian national university in canberra; louise burke andjohn hawley of canberra; anne milne of the sydney morning herald; ian nowak, formerlyof the geological society of western australia; thomas h. rich of museum victoria; timflannery, director of the south australian museum in adelaide; and the very helpful staff ofthe state library of new south wales in sydney.

and elsewhere: sue superville, information center manager at the museum of new zealandin wellington, and dr. emma mbua, dr. koen maes, and jillani ngalla of the kenya nationalmuseum in nairobi.

i am also deeply and variously indebted to patrick janson-smith, gerald howard, mariannevelmans, alison tulett, larry finlay, steve rubin, jed mattes, carol heaton, charles elliott, david bryson, felicity bryson, dan mclean, nick southern, patrick gallagher, larryashmead, and the staff of the peerless and ever-cheery howe library in hanover, newhampshire.

above all, and as always, my profoundest thanks to my dear wife, Cynthia.