Cavalli-Sforza is one of the leading human geneticists and has long been interested in using surveys of the genetic diversity of populations to reconstruct the long-range history of the human species. This book, translated from the French, offers a semi-popular account of what he and his colleagues’ research has revealed over the past several decades. It also seeks to correlate the genetic information with what can be learned from archaeology, cultural history and, more especially the development of languages.

The basic starting point of the expansion which generated the present world-wide population of human beings is by now well known. Against the opposition of some palaeoanthropologists, the geneticists have shown that the archaic humans who spread around the old world hundreds of thousands of years ago (including the Neanderthals of Europe) are not ancestral to modern humanity. All modern humans are descended from a population which evolved in Africa and began to spread out across the world between fifty and sixty thousand years ago. Some of the more obvious physical differences which evolved in the populations of different areas, skin colour and the like, were probably generated by natural selection adapting our ancestors to different environments. But the vast amount of genetic diversity within the human species is hidden, having no immediately recognisable effect on physical appearance, and it is by surveying this diversity that Cavalli-Sforza hopes to reconstruct phylogenetic trees linking the populations of different areas, and then the migrations of the peoples who contributed to that diversity. The first great migration was by hunter-gatherers with only the most primitive means of transportation who exited Africa through the Middle-East or along the coast of South Asia. Later mass migrations were driven by the invention of agriculture and, eventually, by better means of transportation.

By applying a technique known as Principle Component Analysis, Cavalli-Sforza and his colleagues can chart the genetic residue of successive migrations in a diverse modern population. Applied to Europe, this technique yields five components whose variation can be correlated with known or assumed migrations. The first seems to be linked to the spread of agriculture (showing that this was transmitted by migration, not by the acquisition of the new skills by existing populations). The last shows a concentration in the Basque region of France and Spain and seems to mark the residue of the first modern humans to invade Europe. The genetic techniques also show roughly when and by what routes humans spread across Asia to Australia (surprisingly rapidly) and eventually across the Bering Strait into the Americas. Correlations with what we know about the origin of and relationships between the main language groups suggest that the new populations of the various regions not only had their own genetic identity, but were also isolated enough to develop their own languages – although of course people have occasionally acquired new languages, especially after they have been conquered.

One thing is clear from the very start of Cavalli-Sforza’s account: his passion to undermine the alleged biological foundations for the racist sentiments that plague so much of human relationships. The genetical structure of each region’s population is so complex, and changes so continuously across its geographical range, that all hope of identifying distinct genetic types equivalent to the races of old-fashioned physical anthropology has to be abandoned. Yet is there not a sense in which Cavalli-Sforza’s approach merely transfers the typological approach into the past? Modern populations are mixed, and become ever more mixed as transportation improves – but the diversity is still composed of the residues of past influxes of what must have been genetically fairly homogeneous groups. There is an obvious explanation of why this should be so, related to what evolutionists call the founder effect. If the first expansion of humans around the world, driven by only the most basic means of transportation (walking and rafting) created relatively isolated populations in the various regions, those populations would each have expanded from a small band of founders who first penetrated the region, and the very smallness of that founding group would have defined a limited range of genetic diversity among their descendants. The similarity of these hypothetical ancient genetic groupings to the old concept of unique racial types is unfortunate. Over-simplified popularisations of the new genetics in areas of racial tension such as the Basque region are certainly being picked up by demagogues anxious to claim that their people have a biological identity after all.

A final point of concern centres on the number of individuals whose genetic makeup is used to identify the population of their region. In some cases, at least, a very small number of individual genotypes has been used as the basis of quite bold generalisations about the structure and origin of the population to which they belong. In these circumstances, the possibility of errors due to a bias in the sample is high, and it is worrying to find that there is no discussion of this problem in the book under review. I recently heard an anthropologist who specialises in the Basques challenge the geneticists to show that the evidence for the region’s unique status as a reservoir of ancient genes was not an artefact of the unnaturally large number of Basques who have been sampled compared to the inhabitants of all other parts of Europe. He claimed to have had no satisfactory response. I have no expertise to comment on, let alone resolve, this issue, but it is worth bearing in mind that not everyone is comfortable with the current status of this area of research.

Professor Peter J. Bowler
Anthropological Studies
The Queen’s University of Belfast.