I just finished reading Gregory Cochran’s and Henry Harpending’s 2010 book “The 10,000 Year Explosion: How Civilization Accelerated Human Evolution.” In some senses this book seems to be a rebuttal of Jared Diamond’s book “Guns, Germs and Steel, The Fates of Human Societies.” Diamond’s thesis was that geography was the basis for all the differences between the levels of human technological progress across the world. The underlying message of Diamond’s book is that all humans are exactly the same biologically. An Australian Aborigone and Albert Einstein are equally likely to discover general relativity as long as they were both living in Eurasia at the right time in the right place. In my review of Diamond’s book I stated that the results of geographic isolation clearly had great impact on the ability of neighboring peoples to benefit from the latest technological technology discoveries. But I also doubted that this provided any proof that there were no meaningful differences between different human population groups.
“The Ten Thousand Year Explosion” is the answer to Diamond’s assertion on equivalence of human populations. Cochran and Harpending provide a thesis on why human populations would differ and then a litany of examples of where they do. The book is a fascinating story of how modern humans expanded out of Africa at the end of the last Ice Age and interacted and replaced the archaic humans who preceded them in colonizing Eurasia. It is truly amazing that in a few short years Neanderthals and other archaic humans have gone from a few bones sitting in a museum display to creatures whose DNA can be compared gene by gene with our own. Cochran and Harpending examine the genetic evidence and put forth the case that hybridization of modern humans with Neanderthals in Europe is the most likely explanation for the explosion of genetic and cultural changes that occurred when these two human populations interacted. Their thesis is that the introduction of new alleles (genetic options) gave these humans added flexibility to adapt to their new environment and this led to selection for physical and mental characteristics that in turn gave rise to advances in agriculture, technology, culture and language.
Another message that Cochran and Harpending stress is that human evolution has not slowed even now. A final example to reinforce this idea is the case of the Ashkenazi Jews. Cochran and Harpending analyze the history of the Ashkenazi people and the genetic linkage between their higher average intelligence as a group and a number of genetic diseases that are linked to brain function. He points out that these changes occurred in a period of less than a thousand years and are the result of natural selection reinforced by reproductive isolation and selective advantage based on occupation.
The 10,000 Year Explosion is a fascinating book. You’ll learn that there literally was a tribe that gave rise to all the Indo-European speaking tribes (Celts and Greeks and Romans and Slavs and Germans and Aryans) and that this pastoral tribe went on to conquer and mix with people over half of Eurasia because they could digest lactose in milk. And they were epic poets in Ireland, Greece and India. The book is full of interesting facts and thought provoking ideas. And I think it will convince most people that Jared Diamond is only looking at half the story by neglecting the genetic and other physical evidence about human history that is now available to scientists. It turns out nature and nurture are inextricably linked and progress breeds change and vice versa. We continue to change and to deny this is silly and counterproductive.