Bill Bryson - A short history of nearly everything

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-even 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.