SURVIVAL OF THE WEAKEST

A fox (canis fulvipes), of a kind said to be peculiar to the island, and very rare in it, and which is a new species, was sitting on the rocks. He was so intently absorbed in watching the work of the officers, that I was able, by quietly walking up behind, to knock him on the head with my geological hammer.

—Charles Darwin, Journal of Researches, December 6, 1834

IN THE HIGH ALPS a 5,000-year-old frozen corpse, "Ötzi the Ice Man," lay beside his longbow. The axe marks had not been smoothed off, but the functional aspects were complete—it was a replacement weapon, made in haste. We know he was a man in a hurry: sophisticated forensic archaeological analysis has revealed his story, from the sequence of inhaled tree pollens in his lungs, characteristic of different altitudes, to his stomach contents and the scans that show a rib broken only days before death. He had, my Austrian colleagues are now convinced, been on the run, up mountains and down valleys, for several days, living rough, pursued, desperate to rearm himself, and finally driven toward a high mountain pass with a blizzard threatening. There he was shot in the back from a distance by an expert. Still running, he reached back to grasp the shaft where it projected beneath his shoulder blade; it snapped, leaving the flint arrowhead lodged. The internal bleeding was unstoppable, and by now out of sight of his enemies, he collapsed into the first heavy snow of winter and died. Ice closed over him, and he vanished from memory until 1991, when global warming, acting on the Ötztal glacier, melted him back into view. By the time of Ötzi's death, in the later Neolithic period around 3300 B.C., human beings had long been the planet's top predator, fearing mostly each other.

Before Ötzi died, he had been a farmer who, from time to time, also hunted. He was part of a wave of colonization and economic change that had been sweeping into central Europe from the Balkans (and ultimately western Asia) since 5500 B.C. His ancestors had carved out territory in a zone previously dominated by dedicated wilderness dwellers. These were people who had never had domestic animals or fenced off land. They were mobile and innovative bands of men, women, and children who hunted, fished, and gathered. Their communities had expanded rapidly into the burgeoning new forests of Europe around 10,000 years ago, after the ice sheets receded and the climate quickly warmed. These Mesolithic people were in turn descended from big-game hunters whose lineage can be traced back to a time when mammoth-hunting scenes were painted on cave walls.

This period, the Upper Paleolithic, was when the previous lords of Europe, the Neanderthals, were being squeezed out by our kind, anatomically modern Homo sapiens, first arriving from the Near East around 40,000 years ago. Neanderthals had weathered successive periods of advancing and retreating ice over the previous quarter of a million years. Before them had been Homo heidelbergensis, and, yet further back, Homo erectus. The sequence of kinds of humans, and kinds of human culture, arriving in waves over the hundreds of millennia before Ötzi's death is at least as complex as the history of Europe since that date. To understand how Ötzi (and we) came to look physically modern, to be able to think intelligently and make use of tools and weapons, we will have to track back far earlier, to a point even before there were humans.

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I am unconvinced by the current understanding of our evolution— not whether or when evolutionary changes took place, but how and why. Like my academic colleagues, I have no doubt that humans emerged over vast spans of time, that our distant ancestors were apes, and that we are biological creatures. The results of each new field season of research in paleoanthropology—a new pelvis from Ethiopia, a different sort of small-headed Homo erectus from the high Caucasus Mountains, a new, very early tree-living ape that might be placed on or off our direct ancestral line according to highly technical arguments and scholarly taste—important as they are, do not change the basic fact that humans evolved from apes.

This simple fact is often misunderstood: "If we evolved from chimpanzees, then why are there still chimpanzees?" asked one child, after an introductory lecture I had given his school class, sure that he had spotted the killer weakness in the evolution argument. The answer, of course, is that we didn't. Chimpanzees have evolved alongside us since a point, maybe 7 million years ago, when we formed a single breeding community of some kind of ape. That ape, whatever it was, was much more like a chimpanzee than like us, and that means that modern chimpanzees have not evolved as dramatically as we have. One group of apes continued doing what they had been doing pretty successfully. They may have moved down from trees more, and evolved knuckle-walking, but they never walked fully upright. They kept their insulating fur, never finding a need for clothes, never freeing up their hands to make them, or developing brains large enough to think of them. The other group, split off perhaps by a simple fact of geography, got embroiled in something else. What happened to them was very different and very varied: before we emerged as the only surviving upright-walking ape, there were numerous prototypes, most of them evolutionary dead ends.

Darwin had no access to the African fossil record—he suspected it might exist, but he did not live long enough to see even the first finds. But he did apply some smart thinking to the living species of ape he knew about. He considered it significant that two kinds of great ape— gorillas and chimpanzees (two species of each are now recognized)— lived in the wild in Africa while only one—the orangutan (also now divided into two species)—lived wild outside it, in southeast Asia. Using the same logic he had applied to the evolution of birds and fish, Darwin argued that Africa, as home to the most kinds of great ape, should be the continent on which the common ancestor of apes and humans had lived. He predicted, in advance of the fossil evidence, that it would be there that any intermediate "missing links" would be discovered.

Darwin upheld his African origin theory even after the discovery of the first Neanderthal skeleton in Germany, believing (correctly, as it turns out) that Neanderthals were relatively modern, being a parallel line of later human evolution and not an intermediate link with apes. It was nearly a decade after Darwin's death that the first physical evidence for a missing link came to light, at Trinil in Java. Although "Java Man," now classified as Homo erectus, was, like the orangutan, also outside Africa, paleontological fieldwork throughout the twentieth century and up to the present shows that the most significant phases of human...