The 10,000 Year Explosion (75 Books – XXXIX)

I should probably begin with a disclaimer that I’m very much a layman when it comes to biology and genetics; my experience in the field is limited to a couple college classes. That said, I read and greatly enjoyed The 10,000 Year Explosion, by Gregory Cochran and Henry Harpending, which covers recent human evolution, essentially from the development of agriculture on. The authors accomplish a difficult task of explaining a fairly complex topic in terms that the average, non-specialist reader can understand, while still covering the topic adequately and not coming across as condescending. In fact, the tone is fairly light throughout, reminding me of some of my better college professors who took an almost conversational tone during lectures, with occasional touches of humour. In discussing how genes spread between populations, for example, they drily note, “Sailors and barmaids, like traveling salesmen and farmers’ daughters, have played a crucial role in recent human evolution.”

Besides fairly abstract discussions of the technicalities of how human genetics and natural selection work, they also have a number of interesting illustrations of recent evolution. For example, while going over changes in skeletal structure, they provide a recent study from England:

English researchers recently compared skulls from people who died in the Black Death (≈650 years ago), from the crew of the Mary Rose, a ship that sank in Tudor times (≈450 years ago), and from our contemporaries. The shape of the skull changed noticeably over that brief period—which is particularly interesting because we know there has been no massive population replacement in England over the past 700 years. The height of the cranial vault of our contemporaries was about 15 percent larger than that of the earlier populations, and the part of the skull containing the frontal lobes was thus larger.

The 10,000 Year Explosion reminds me of Nicholas Wade’s book from last year, A Troublesome Inheritance, which covers biological racial differences, and which I’d also recommend reading for those interested in the topic. Both works are interesting in themselves, of course, but those of us more invested in politics than science will find it noteworthy that they were published at all. Wade addresses the racial angle head-on, though not polemically, but Cochran and Harpending take a different approach. They only mention the “controversy” around the topic a few times, and always dismissively. In the concluding chapter, for example, they say, “Evolutionary stasis requires a static environment, whereas behavioral modernity is all about innovation and change. Stability is exactly what we have not had. This should be obvious, but instead the human sciences have labored under the strange idea that evolution stopped 40,000 years ago.”

Also, while Wade does not directly address intelligence differences, Cochran and Harpending devote a chapter to exploring how Ashkenazi Jews came to have the highest average IQ in the world. In that chapter, they mention that there is a lot of controversy about the validity of IQ testing, but add, “These criticisms and dismissals, interestingly, hardly ever come from scientists working in the area of cognitive testing and its outcomes: There is little or no controversy within the field.” This correlates with comments by Wade and a few other people I’ve encountered who’ve studied the topic, and it’s interesting to me as an example of selective credentialism. How often do we see publications emphasise how widely theories of global warming are accepted by climatologists, almost always coupled with harsh criticism of the non-experts who question the scientists’ conclusions? Yet, the validity of intelligence testing is also widely accepted by experts, and is treated as if it’s highly controversial!

In any case, Cochran and Harpending’s topic is an important one, and I’d highly recommend that anyone at all interested give it a read.

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