A Short History of Nearly Everything

by Bill Bryson

  "It turned everything upside down again," says Thorne with undisguised delight.

  Then other even more curious anomalies began to turn up. Rosalind Harding, a population geneticist at the Institute of Biological Anthropology in Oxford, while studying betaglobin genes in modern people, found two variants that are common among Asians and the indigenous 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 Homo sapiens reached the region. The only way to account for them is to say that ancestors of people 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 in Oxfordshire.

  Confused, I went to see Harding at the institute, which inhabits an old brick villa on Banbury Road in Oxford, in more or less the neighborhood where Bill Clinton spent his student days. Harding is a small and chirpy Australian, from Brisbane originally, with the rare knack for being amused and earnest at the same time.

  "Don't know," she said at once, grinning, when I asked her how people in Oxfordshire harbored sequences of betaglobin that shouldn't be there. "On the whole," she went on more somberly, "the genetic record supports the out-of-Africa hypothesis. But then you find these anomalous clusters, which most geneticists prefer not to talk about. There's huge amounts of information 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 can say 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 had just produced a popular book called The Seven Daughters of Eve in which, using studies of mitochondrial DNA, he had claimed to be able to trace nearly all living Europeans back to a founding population of just seven women--the daughters of Eve of the title--who lived between 10,000 and 45,000 years ago in the time known to science as the Paleolithic. To each of these women Sykes had given a name--Ursula, Xenia, Jasmine, and so on--and even a detailed personal history. ("Ursula was her mother's second child. The first had been taken by a leopard when he was only two. . . .")

  When I asked Harding about the book, she smiled broadly but carefully, as if not quite certain where to go with her answer. "Well, I suppose you must give him some credit for helping to popularize a difficult subject," she said and paused thoughtfully. "And there remains 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 the mitochondrial DNA backwards, it will take you to a certain place--to an Ursula or Tara or whatever. But if you take any other bit of DNA, any gene at all, and trace it back, it will take you someplace else altogether."

  It was a little, I gathered, like following a road randomly out of London and finding that eventually it ends at John O'Groats, and concluding from this that anyone in London must therefore 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 to map 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 the sweeping conclusions that people often attach to them."

  She thinks out-of-Africa is "probably 95 percent correct," but adds: "I think both sides have done a bit of a disservice to science by insisting that it must be one thing or the other. Things are likely to turn out to be not so straightforward as either camp would have you believe. The evidence is clearly starting to suggest that there were multiple migrations and dispersals in different parts of the world going in all kinds of directions and generally mixing up the gene pool. 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 claims concerning the recovery of very ancient DNA. An academic writing in Nature had noted how a 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, "large amounts of modern human DNA would have been transferred to the skull," rendering it useless for future study. I asked Harding about this. "Oh, it would almost certainly have been contaminated already," she said. "Just handling a bone will contaminate it. Breathing on it will contaminate it. Most of the water in our labs will contaminate it. We are all swimming in foreign DNA. In order to get a reliably clean specimen you have to excavate it in sterile conditions and do the tests on it at the site. It is the trickiest thing in the world not to contaminate 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, I have the place for you. It is to be found a little beyond the edge of the blue Ngong Hills in Kenya, to the south and west of Nairobi. Drive out of the city on the main highway to Uganda, and there comes a moment of startling glory when the ground falls away and you are presented 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 miles out of Nairobi, along the baking valley floor, is an ancient site called Olorgesailie, which once stood beside a large and pleasant lake. In 1919, long after the lake had vanished, a geologist named J. W. Gregory was scouting the area for mineral prospects when he came across a stretch of open ground littered with anomalous dark stones that had clearly been shaped by human hand. He had found one of the great sites of Acheulean tool manufacture that Ian Tattersall had told me about.

  Unexpectedly in the autumn of 2002 I found myself a visitor to this extraordinary site. I was in Kenya for another purpose altogether, visiting some projects run by the charity CARE International, but my hosts, knowing of my interest in humans for the present volume, had inserted a visit to Olorgesailie into the schedule.

  After its discovery by Gregory, Olorgesailie lay undisturbed for over two decades before the famed husband-and-wife team of Louis and Mary Leakey began an excavation that isn't completed yet. What the Leakeys found was a site stretching to ten acres or so, where tools were made in incalculable numbers for roughly a million years, from about 1.2 million years ago to 200,000 years ago. Today the tool beds are sheltered from the worst of the elements beneath large tin lean-tos and fenced off with chicken wire to discourage opportunistic scavenging by visitors, but otherwise the tools are left just where their creators dropped them and where the Leakeys found them.

  Jillani Ngalli, a keen young man from the Kenyan National Museum who had been dispatched to act as guide, told me that the quartz and obsidian rocks from which the axes were made were never found on the valley floor. "They had to carry the stones from there," he said, nodding at a pair of mountains in the hazy middle distance, in opposite directions from the site: Olorgesailie and Ol Esakut. Each was about ten kilometers, or six miles, away--a long way to carry an armload of stone.

  Why the early Olorgesailie people went to such trouble we can only guess, of course. Not only did they lug hefty stones considerable distances to the lakeside, but, perhaps even more remarkably, they then organized the site. The Leakeys' excavations revealed that there were areas 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 to make--eve
n with practice, an axe would take hours to fashion--and yet, curiously, they were not particularly good for cutting or chopping or scraping or any of the other tasks to which they were presumably put. So we are left with the position that for a million years--far, far longer 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 make extravagantly 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 Homo erectus because there are no other known candidates, which means that at their peak--their peak --the Olorgesailie workers would have had the brains of a modern infant. But there is no physical evidence on which to base a conclusion. Despite over sixty years of searching, no human bone has ever been found in or around the vicinity of Olorgesailie. However much time 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 lake dried up and the Rift Valley started to become the hot and challenging place it is today. But by this time their days as a species were already numbered. The world was about to get its first real master race, Homo sapiens . Things would never be the same again.

  30 GOOD-BYE

  IN THE EARLY 1680s, at just about the time that Edmond Halley and his friends Christopher Wren and Robert Hooke were settling down in a London coffeehouse and embarking on the casual wager that would result eventually in Isaac Newton's Principia , Henry Cavendish's weighing of the Earth, and many of the other inspired and commendable undertakings that have occupied us for much of the past four hundred pages, a rather less desirable milestone was being passed on the island of Mauritius, far out in the Indian Ocean some eight hundred miles off the east coast of Madagascar.

  There, some forgotten sailor or sailor's pet was harrying to death the last of the dodos, the famously flightless bird whose dim but trusting nature and lack of leggy zip made it a rather irresistible target for bored young tars on shore leave. Millions of years of peaceful isolation had 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 the last dodo, so we don't know which arrived first, a world that contained a Principia or one that had no dodos, but we do know that they happened at more or less the same time. You would be hard pressed, I would submit, to find a better pairing of occurrences to illustrate the divine and felonious nature of the human being--a species of organism that is capable of unpicking the deepest secrets of the heavens while at the same time pounding into extinction, for no purpose at all, a creature that never did us any harm and wasn't even remotely capable of understanding what we were doing to it as we did it. Indeed, dodos were so spectacularly short on insight, it is reported, that if you wished to find all the dodos in a vicinity you had only to catch one and set it to squawking, and all the others would waddle along to see what was up.

  The indignities to the poor dodo didn't end quite there. In 1755, some seventy years after the last dodo's death, the director of the Ashmolean Museum in Oxford decided that the institution's stuffed dodo was becoming unpleasantly musty and ordered it tossed on a bonfire. 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 only its head and part of one limb.

  As a result of this and other departures from common sense, we are not now entirely sure what a living dodo was like. We possess much less information than most people suppose--a handful of crude descriptions by "unscientific voyagers, three or four oil paintings, and a few scattered osseous fragments," in the somewhat aggrieved words of the nineteenth-century naturalist H. E. Strickland. As Strickland wistfully observed, we have more physical evidence of some ancient sea monsters and lumbering saurapods than we do of a bird that lived into modern 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, and was the biggest-ever member of the pigeon family, though by quite what margin is unknown as 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 half feet tall and about the same distance from beak tip to backside. Being flightless, it nested on the ground, leaving its eggs and chicks tragically easy prey for pigs, dogs, and monkeys brought to the island by outsiders. It was probably extinct by 1683 and was most certainly gone by 1693. Beyond that we know almost nothing except of course that we will not see its like again. We know nothing of its reproductive habits and diet, where it ranged, what sounds it 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. That is a breathtakingly scanty period--though it must be said that by this point in our history we did 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 fifty thousand years or so wherever we have gone animals have tended to vanish, in often astonishingly large numbers.

  In America, thirty genera of large animals--some very large indeed--disappeared practically at a stroke after the arrival of modern humans on the continent between ten and twenty thousand years ago. Altogether North and South America between them lost about three quarters of their big animals once man the hunter arrived with his flint-headed spears and keen organizational capabilities. Europe and Asia, where the animals had had longer to evolve 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 populations truly monumental--as many as ten million mammoth carcasses are thought to lie frozen in the tundra 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 the American Museum of Natural History put it: "There's no material benefit to hunting dangerous animals more often than you need to--there are only so many mammoth steaks you can eat." Others believe it may have been almost criminally easy to catch and clobber prey. "In Australia and the Americas," says Tim Flannery, "the animals probably didn't know enough to run away."

  Some of the creatures that were lost were singularly spectacular and would take a little managing if they were still around. Imagine ground sloths that could look into an upstairs window, tortoises nearly the size of a small Fiat, monitor lizards twenty feet long basking beside desert highways in Western Australia. Alas, they are gone and we live on a much diminished planet. Today, across the whole world, only four types of really hefty (a metric ton or more) land animals survive: elephants, rhinos, hippos, and giraffes. Not for tens of millions of years has life on Earth been so diminutive and tame.

  The question that arises is whether the disappearances of the Stone Age and disappearances of more recent times are in effect part of a single extinction event--whether, in short, humans are 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 of extinction on Earth throughout biological history has been one species lost every four years on average. According to one recent calculation, human-caused extinction now may be running as much as 120,000 times that level.

  In the mid-1990s, the Australian naturalist Tim Flannery, now head of the South Australian Museum 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 gaps in the records--pieces missing, as with the dodo, or not record
ed at all," he told me when I met him in Melbourne a year or so ago.

  Flannery recruited his friend Peter Schouten, an artist and fellow Australian, and together they embarked on a slightly obsessive quest to scour the world's major collections to find out what was lost, what was left, and what had never been known at all. They spent four years picking through old skins, musty specimens, old drawings, and written descriptions--whatever was available. Schouten made life-sized paintings of every animal they could reasonably re-create, and Flannery wrote the words. The result was an extraordinary book called 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 to the dugong, was one of the last really big animals to go extinct. It was truly enormous--an adult could reach lengths of nearly thirty feet and weigh ten tons--but we are acquainted with it only because in 1741 a Russian expedition happened to be shipwrecked on the only place where the creatures still survived in any numbers, the remote and foggy Commander Islands in 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 its whiskers. The only thing he wouldn't describe was the male genitals--though, for some reason, he was happy enough to do the female's. He even saved a piece of skin, so we had a good 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 brink of extinction, it would be gone altogether within twenty-seven years of Steller's discovery of it. 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.