From a friend:

Interesting bit that Thomas Sowell once cited in arguing against
genetic determinism (though it’s not an air-tight case, since certainly
a gene, like that presumably for schizophrenia, sometimes only evinces
itself in response to environmental stimuli): if you look at the IQ
tests given to U.S. Army soldiers in WW1 (probably evil Woody Wilson’s
version of the SAT!), one of the bottom-ranking groups was “Russians,”
which were mostly Ashkenazi Jews. Seventy years on, the Ashkenazi
Jewish population’s mean score was 15 points higher than the average
white-folks mean. Sowell’s point was to say that the Bell Curve thesis
might be overstated. Certainly, intelligence is heritable, but culture
does a ton to determine how smart you get. I think his basic thesis
was that Jews valued abstract learning as a cultural norm, so that
shtetl folks right off the Pale probably had low IQs because while they
might have valued book-larnin’, they had no opportunities to get it.
However, once in the U.S., they pushed their kids (who pushed their
kids), etc., to grab the (relatively easily available) available book
learning, pushing up their IQs. It’d be interesting to see if the same
were true of, say, Chinese Americans (though I doubt the data’s there),
since that’s another group that came to the U.S. as mostly poor,
illiterate people from a culture that elevated book-learning above all.