[necovek]

There are so many societal and environmental confounding factors, that I don't see how I would ever trust a study that would claim this.

What we are learning so far is that genes tell an extremely complex and probabilistic story.

There is no way we have "evolved" through selection in many countries from 4+ kids to <2 kids per mother in a span of a 100 years, so while we could possibly see such a genetic effect over thousands (probably more) of years, there is no way we could see it in the span of a century.