David Reich

intelligence or actual studiousness or something like that, you should think again because there's many things that it's correlated to.

There seems to be some kind of general trait that maybe you could think of as executive function or maybe propensity to defer gratification or something, or I make just waving my hands that is under selection and it pushes all these traits in the same direction one way or the other.

And in different times in the past, it's advantageous or disadvantageous.

But when we found this signal of years of schooling being increased, the genetic propensity to go to school for more years, as it manifests itself in people, in white British people today, when we found the signal, we were sort of incredulous.

Like, how could this be?

Maybe this is a problem.

So we did a few tests to try to figure out whether this was real.

And one of the tests we did is we looked for a study where this measurement of the numbers of years of school was done not in Europeans,

but was done in Chinese people in China.

And we looked at variants that had the effect size of many variants as they affected the number of years of school in China.

And we saw whether they had a relationship, a correlation to the trajectory of those same genetic variants in Europeans over the last 10,000 years.

So these are two parts of the world where the populations have been essentially completely disconnected.

And there's no way by chance that the trajectory in Europeans

over the last 10,000 years will have anything to do with the number of years, the effect on the years of schooling in China today.

But there's actually a huge statistical correlation, a five or six standard deviation correlation between the effect size of variance, a number of years of school in China today, and the trajectory in Europe, just as strong actually as the effect size of variance in Europeans today.

to the trajectory in Europeans.

So we just could not see a way this could happen by chance.

And once we saw that, we really felt quite convinced that this was a real signal and that really somehow there has been natural selection to increase the genetic changes that today manifest themselves as predicting more years of schooling.

I think that that's a great question.

As we talked about before, the human selection is very effective.