Book review: The 10,000 Year Explosion: How Civilization Accelerated Human Evolution by Gregory Cochran and Henry Harpending.
This provocative book describes many recent genetic changes in humans, primarily those resulting from the switch from hunter-gatherer lifestyles to agricultural lifestyles. Large changes in diets and disease are the simplest causes of change, but the book also describes subtler influences that alter human minds as well.
I had believed that large populations rarely evolve very fast due to the time required for a mutation to spread. This is true for mutations which provide negligible selective advantage, but the book shows that it’s plausible that a number of mutations have recently gained a large enough selective advantage that the rate at which they become widespread is only modestly dependent on population size. Also, the book makes a surprising but plausible claim that the larger supply of mutations in large populations can mean large populations evolve faster than small populations.
The book is occasionally not as rigorous as I would like. For instance, the claim that Ashkenazi “must have been exposed to very similar diseases” as their neighbors is false if the diseases were sexually transmitted.
Most of their claims convince me that conventional wisdom underestimates how important human genetic differences compared to cultural differences, but leave plenty of room for doubt about the magnitude of that underestimation.
They provide an interesting counterargument to the claim that differences within human populations are larger than the differences between populations. Their belief that differences between populations are more important seems to rest on little more than gut feelings, but they convince me that the conventional wisdom they’re disputing is poorly thought out.
They convinced me to take more seriously the possibility that some Neanderthal genes have had significant effects on human genes, although I still put the odds on that at less than 50 percent.