[Chen77]

Who is they?

What I find amazing is that people are surprised that group differences have arisen over the last 50,000 years. Gene-culture coevolution makes it seem inevitable that different cultures will favor different traits. Therefore you're going to see some average differences.

There are obvious examples, a more polygamous society where women do more of the work (eg female farming systems) with lower paternal investment, might favor different traits to those where there is State control, monogamy and greater paternal investment.

I'd recommend that you read some posts by Steve Hsu, Peter Frost, or 'The 10,000 Year Explosion: How Civilization Accelerated Human Evolution'.