The Origin of Our Species

And God said, let there be culture. And there was culture. Then came technology, art, writing and, eventually, books. Some books featured more convincingly detailed stories about how it all started. How did one primate species become capable of asking, well, how one primate species became capable of asking?

This is the question animating Chris Stringer's latest popular account of human origins. It lacks the lavish illustrations of his last book, Homo Britannicus: The Incredible Story of Human Life in Britain (2006), but ranges more widely, considering the history of humans across the globe, not just in the British Isles. And it looks back over a 40-year career, in which both the techniques of palaeoanthropology and our understanding of prehistory have been transformed.

In 1970, a dogged research student with a road map of Europe could still compile hand measurements of fossil skulls from scattered museums and make worthwhile new inferences about evolutionary relationships, as Stringer did. Since then, a welter of new archaeological finds, more refined dating methods and, most recently, genetic analysis have enriched the picture of which varieties of proto-humans emerged, where.

Together, they support the idea that all modern humans descend from a smallish band of emigrant Homo sapiens from Africa who lived about 60,000 years ago. Stringer was an early proponent of this interpretation, in the face of the prevailing orthodoxy that proto-humans left Africa first, then became "modern" in several other places. It is now largely confirmed, although the very latest molecular genetic analyses are complicating the story. The full genome of European Neanderthals has been worked out from 40,000-year-old DNA, for instance, one of the most remarkable scientific achievements of the past couple of years. The small amount of genetic material they shared with us suggests some interbreeding between the two types before the Neanderthals disappeared.

This is just one strand in a scientific story that weaves together many different kinds of evidence - from the growth patterns in fossil teeth to fashions in flints and the co-evolution of humans and body lice. If you like authority in your popular science, this one is a good bet. The author pretty much owns the subject. On the whole, that is a good thing. There is as much detail as you could wish for, and perhaps even a bit more than that in the chapters on digs, dates and skull dimensions.

Stringer's own extensive contributions are generally introduced in the tone of "here's another interesting thing", rather than "look what I did". He does stress how fiercely the out-of-Africa thesis was resisted through the 1980s and beyond, but has now largely been vindicated. But he does not suggest that the final word has been voiced just yet. And he is scrupulous about distinguishing hard data from speculation, and well aware that the species we are all trying to understand likes to join the dots of sparse data with stories that are little more than plausible.

And if it did start in Africa, what triggered the human cultural explosion? How did we become conscious of being conscious? The best answer, he believes, is that a large continent supported a good-sized population over many generations, thus allowing the gradual emergence of many small changes in form and behaviour. Then cultural innovations accumulated, through innovation and imitation. They all eventually added up to a change of state.

The conclusion is tentative and sounds a strong note of contingency. We are as we are, but could easily have been otherwise, or not have survived - or existed - at all. Then some other sub-species of the genus Homo might be reconstructing the story of its lost origins.