David Reich, in his book, made an important point that I noticed but did not emphasize. The plus variants for educational attainment are getting rarer at a rapid pace in Iceland and the US ( and probably all other developed countries), corresponding to a drop in IQ of about a point a generation – which is about what you would expect from heritability and known demographic patterns, something which has been known from before I was born.
Reich points out that it’s pretty hard to believe that selection A. couldn’t or B. just wouldn’t change IQ in different populations [ given tens of thousands of years], if it is changing things right in front of our eyes. If selection had different effects on IQ in different eras, it almost certainly had different effects in different places.
Along this same line of thought, we may expect to see differences in IQ in past European populations, extrapolated from ancient DNA.