The 10,000 Year Explosion: How Civilization Accelerated Human Evolution, by Gregory Cochran and Henry Harpending, Basic Books, RRP$16.95, 288 pages
There are many “ifs” and few “buts” in this tantalising book in which two anthropologists argue that humankind is still being shaped, physically and mentally, by the blind forces of evolution.
This belief runs counter to received wisdom, they say. Social scientists believe that human evolution essentially came to a full stop some 50,000 years ago – roughly about the time that modern humans were beginning to migrate out of Africa.
Yet Cochran and Harpending argue that “human evolution has accelerated in the past 10,000 years rather than slowing or stopping, and is happening about 100 times faster than its long-term average over the 6m years of our existence”. The two University of Utah professors take as their starting point a dramatic technological and cultural advance after the African exodus, which saw intelligent man – Homo sapiens – become the dominant hominid and spelled extinction for the neanderthals.
But, they claim, the Neanderthals left a genetic legacy, which puts them in the camp of those who believe there was copulation between Homo sapiens and Homo neanderthalensis. They go on to argue that these ancient genes were important in the cultural explosion that led to civilisation. Just as important was the development of agriculture, which resulted in big changes in diet, exposure to disease and social structures. These changes led to evolutionary developments – the ability of certain human groups to digest cows’ milk, for example.
By the same token, some groups were resistant to particular diseases while others succumbed. The authors point out that the Spanish adventurer Cortés could not have conquered the Aztec empire with just a few hundred men had the native Amerindians not been almost wiped out by European diseases.
Cochran and Harpending take the Ashkenazi Jews, who settled along the Rhine more than a millennium ago, as their principal proof that humankind is continually evolving. The Ashkenazi Jews have the highest intelligence quotient of any known ethnic group, because they have “a genetic advantage in intelligence that arose from natural selection for success in white-collar occupations during their sojourn in northern Europe”.
Interestingly, the authors make no predictions for our future. And accordingly, biologists – as opposed to social scientists – may not find their thesis all that novel. But it is an engaging book with valuable information about how advantageous genes spread through a population.
Alan Cane is an FT science writer