Interesting. My problem with The Bell Curve is different. There are two issues. One is, how do you define a group. Since all psychological traits have now been shown as resulting from a combination of genes and environment, nature and nurture, defining a group n an ethnic basis is not easy. The Bell Curve talked about blacks, and that is a group which is not genetically close enough to talk about ethnicity. Ashkenazi Jews may well be the only major group in the world which fits the bill – even Sephardi Jews are much more widely scattered in a genetic sense.

My second quibble is that if you want to compare the average IQ of two groups you needd them to be identical in every respect but one. Income and income distribution, education, places of residence, jobs and so on – and to have rather big samples. In genetics research, samples of at least tens of thousands are needed if you want meaningful results – hundreds of thousanda are now widely used. The Bell Curve got nowhere near that. I wonder if their results have even been replicated independently – if not, the resuts are meaningless.