Nicholas Wade

BEFORE THE DAWN

Recovering the Lost History of Our Ancestors

Wade places the exodus of modern humans from Africa at a fairly late date, probably only some 50,000 years ago. Genetic studies had implied a somewhat earlier departure but the archaeological evidence, he thinks, favours the later date. The route taken by our ancestors was probably across the southern end of the Red Sea. As to why modern humans didn't leave Africa earlier, Wade suggests that they would have been inhibited by the presence of Neanderthals, but in view of the low density of Neanderthal populations I wonder how much of a deterrent that would really have been.

Once across the straits, the human population spread quite rapidly, reaching Australia within a surprisingly short time. But Wade makes the important point that this dispersion wasn't planned or evidence of a zeal for exploration; it happened simply because hunter–gatherer groups tend to split up and move on once the resources of an area are exhausted. Migration was mainly along the coast, but Europe was colonised within about 5,000 years.

Some of Wade's views are likely to surprise and perhaps offend some readers, but it is all to the good that he doesn't shirk contentious topics. We are sometimes told that our hunter–gatherer ancestors lived peaceful lives without inter-group conflict, but Wade finds that warfare has always been endemic in our species, a trait that we probably inherit from the last common ancestor we share with chimpanzees.

He also tackles the issue of race. In appearance, the modern humans who left Africa were almost certainly black, but after Europe was colonised there would have beeen evolutionary pressure to favour lighter pigmentation to allow better synthesis of vitamin D. The Neanderthals were probably also pale, for the same reason.

We tend to think that humans have changed little if at all in the last 50,000 years, but Wade presents evidence for at least two brain genes that have evolved in the last 40,000 years. One, microcephalin, appeared about 37,000 years ago and is now widespread among Caucasians and East Asians but is much less common among sub-Saharan Africans. Another, ASPM, is found among Caucasians but is less common among East Asians and is almost unknown in sub-Saharan Africans. There may be other genetic differences that are as yet undiscovered. But the significance of such changes remains to be determined.

Wade has a good deal of discussion of language and its evolution. He finds that the use of different kinds of click in speaking, as in the !Kung language, is probably a primitive characteristic and may give a clue to the form of speech of our African ancestors. And he even thinks that the attempt to discover echoes of the first language may not be completely hopeless. Not all linguists agree with this assessment of the antiquity of clicks, however.

There is a tendency among some sociologists to downplay the relevance of evolution to human behaviour. Wade, in contrast, places evolution at the centre of the story; every chapter begins with a quotation from Darwin.

Evolution and history are not two distinct processes, with one following another like the change between two royal dynasties. Rather, evolution and history overlap, with the historical period being overlaid on a still continuing process of evolutionary change.

14 August 2010