Instead, different ethical constraints should apply to research on different species. Perhaps it is just our naked selfishness, re-emerging in a new disguise, that would advocate granting special rights to those animal species genetically closest to us. But an objective case, based on the considerations I have just mentioned (intelligence, social relationships, etc.), can be made that chimps and gorillas qualify for preferred ethical consideration over insects and bacteria. If there is any animal species currently used in medical research for which a total ban on medical experimentation can be justified, that species is surely the chimpanzee. The ethical dilemma posed by animal experiments is compounded for chimps by the fact that they are endangered as a species. In this case, medical research not only kills individuals but threatens to kill the species itself. That is not to say that demands for research have been the sole threat to wild chimp populations—habitat destruction and capture for zoos have also been major threats—but it is enough that research demands have been a significant threat. The ethical dilemma is further compounded by other considerations: that on the average several wild chimps are killed in the process of capturing one (often a young animal with its mother) and delivering it to a medical research laboratory; that medical scientists have played little role in the struggle to protect wild chimp populations, despite their obvious self-interest in doing so; and that chimps used for research are often caged under cruel conditions. The first chimp that I saw being used for medical research had been injected with a slow-acting lethal virus and was being kept alone, for the several years until it died, in a small, empty, indoor cage at the US National Institutes of Health. Breeding chimps in captivity for research use avoids objections based on depleting wild chimp populations, but that still does not get around the basic dilemma, any more than enslaving children of US-born blacks after abolition of the African slave trade made black slavery in the nineteenth-century US acceptable. Why is it all right to experiment on Homo troglodytes, but not on Homo sapiens'? Conversely, how should we explain to parents, whose children are at risk of dying from diseases now being studied in captive chimps, that their children are less important than chimps? Ultimately, we the public, not just scientists, will have to make these terrible choices. All that is certain is that our view of man and apes will determine our decision. Finally, changes in our attitudes about apes may be crucial in determining whether apes will survive at all in the wild. At present, their populations are threatened especially by destruction of their rainforest habitats in Africa and Asia, and by legal and illegal capture and killing. If present trends continue, the mountain gorilla, orangutan, pileated gibbon, Kloss's gibbon, and possibly some other apes as well will exist only in zoos by the time that this year's crop of human babies enters college. It is not enough for us to preach to the governments of Uganda, Zaire, and Indonesia about their moral obligation to protect their wild apes. These are impoverished countries, and national parks are expensive to create and maintain. If we as the third chimpanzee decide that the other two chimpanzees are worth saving, those of us in the richer countries will have to bear most of the expense. From the point of view of the apes themselves, the most important effect of what we have recently learned about the Tale of Three Chimps will be on how we feel about footing that bill.
TWO
THE GREAT LEAP FORWARD
What happened at that magic moment in evolution around 40,000 years ago, when we suddenly became human?
As we saw in Chapter One, our lineage diverged from that of apes millions of years ago. For most of the time since then, we have remained little more than glorified chimpanzees in the ways we have made our living. As recently as/40,000 years ago, Western Europe was still occupied by Neanderthals, primitive beings for whom art and progress scarcely existed. Then there was an abrupt change, as anatomically modern people appeared in Europe, bringing with them art, musical instruments, lamps, trade, and progress. Within a short time, the Neanderthals were gone. That Great Leap Forward in Europe was probably the result of a similar leap that had occurred over the course of the preceding few tens of thousands of years in the Near East and Africa. Even a few dozen millenia, though, is a trivial fraction (less than one per cent) of our millions of years of history separate from that of the apes. Insofar as there was any single point in time when we could be said to have become human, it was at the time of that leap. Only a few more dozen millenia were needed for us to domesticate animals, develop agriculture and metallurgy, and invent writing. It was then but a short further step to those monuments of civilization that distinguish humans from animals acros's what used to seem an unbridgeable gulf- monuments such as the 'Mona Lisa' and the Eroica Symphony, the Eiffel Tower and Sputnik, Dachau's ovens and the bombing of Dresden.
This chapter will confront the questions posed by our abrupt rise to humanity. What made it possible, and why was it so sudden? What held back the Neanderthals, and what was their fate? Did Neanderthals and modern peoples ever meet, and if so, how did they behave towards each other?
Understanding the Great Leap Forward is not easy, and writing about it is not easy either. The immediate evidence conies from technical details of preserved bones and stone tools. Archaeologists' reports are full of terms obscure to the rest of us, such as 'transverse occipital torus', 'receding zygomatic arches', and 'Chatelperronian backed knives'. What we really want to understand—the way of life and the humanity of our various ancestors—is not directly preserved but only inferred from those technical details of bones and tools. Much of the evidence is missing, and archaeologists often disagree over the meaning of such evidence as has survived. Since the books and articles listed on pages 334-5 will slake the interest of readers curious to learn more about receding zygomatic arches, I shall emphasize instead the inferences from bones and tools.
Our ancestors were confined to Africa for millions of years, where, as we have already discussed, they diverged from the ancestors of chimps and gorillas between about six and ten million years ago. For comparison, life originated on Earth several billion years ago, and the dinosaurs became extinct around sixty-five million years ago. (Science-fiction films that depict cavemen fleeing from dinosaurs are just that, science fiction.) Initially, our ancestors would have been classified as merely another species of ape, but a sequence of three changes launched us in the direction of modern humans.
The first of these changes had occurred by around four million years ago, when the structure of fossilized limb bones shows that our ancestors were habitually walking upright on the two hindlimbs. In contrast, gorillas and chimps walk upright only occasionally, and usually proceed on all fours. The upright posture freed our ancestors' forelimbs to do other things, among which tool-making proved the most important.
The second change occurred around three million years ago, when our lineage split into at least two distinct species. Recall that members of two animal species living in the same area must fill different ecological roles and do not normally interbreed with each other. For example, coyotes and wolves are obviously closely related and (until wolves were exterminated in most of the US) lived in many of the same areas of North America. However, wolves are larger, mainly hunt big mammals like deer and moose, and often live in large packs, whereas coyotes are smaller, mainly hunt small mammals like rabbits and mice, and usually live in pairs or small groups. Similarly, Europe's wildcat and lynx are closely related and overlap widely in range but differ ecologically and do not interbreed.