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 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 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 around 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 pair of mountains in the hazy middle distance, in the opposite directions from the site: Olorgesailie and Ol Esakut. Each was about ten kilometeres, 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 longer than our own species has even been in existence, much less engaged in continious 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.
