David Reich

And so one possible interpretation of this, sort of hand-wavy, is that actually what's being measured here is not selection for years of schooling or for actually real intelligence, but for another trait altogether that's correlated to both of them.

So for example, the predictor of numbers of years of schooling is very, very strongly correlated to the age at which women have their first kid.

If you control for that for a number of years of schooling, all of the signal of years of schooling goes away.

Maybe what you're measuring is women's decision about when to have children.

If you have children earlier, you don't go to school as much.

If you have children later, you go to school more.

Maybe it's some measurement of delaying gratification or putting things off or planning.

The same trait is correlated to body mass index, to obesity, or to walking pace.

So is this really like intelligence as we think about it?

Or is it something else that manifests itself differently in different times in the past?

Yeah.

Well, I think that there's two things going on that you need to think about.

So one of them is that years of schooling is connected to so many other things genetically.

So if you look at the genetic predictor of years of schooling, that this trait has been measured in millions of people now, it's actually correlated to really, really surprising things.

It's correlated to the age at which women have their first kid.

It's correlated to people's

It's correlated to people's walking pace.

It's correlated to people's household wealth.

It's correlated to a variety of other traits that seem quite different from it.

So if you think you're actually measuring years of genetic prediction of obesity,