David Reich

There's been very strong change in frequency over time where we're confident of, and we think there are many thousands that we can see traces of.

The whole genome is seething with these changes in this period.

So it's very clear.

that there is extreme overrepresentation of change on variants that affect metabolism and immune traits.

And so if you look at traits that we know today affect immune disease or metabolic disease, these traits...

are highly overrepresented by a factor of maybe four in the collection of variants that are changing rapidly over time.

Whereas if you look at traits that are affecting cognition that we know in modern people modulate behavior, they're hardly affected at all.

That is selection in this last 10,000 years doesn't seem to be focusing on average on cognitive and behavioral traits.

It seems to be focusing on immune and cardiometabolic traits.

on average, with exceptions.

But on average, there's an extreme over-representation of cardiometabolic traits.

So one example of this is that there's a very clear downward selection against body fat.

and against predisposition to high body mass index, predisposition to what today manifests itself as type 2 diabetes.

So that genetic combination in West Eurasia has been pushed down again and again over the last 10,000 years under the pressure of natural selection, without a doubt, in its action on many, many independent genetic variants, all pushing in the same direction and overwhelmingly

statistically significant way.

So one possible interpretation of this, and this is speculative, is that you're shifting from a mode of survival that's more feast and famine to one where food is more regular and it's not as advantageous to store fat.

And so there's selection against sort of fat storage.

Well, on a timescale, I mean, selection acts, I don't know how you think selection acts, but at some level, it could be terrible on the individual level and good on the population level.

So I think that, you know, I'm not doubting the evidence that you're, I think, maybe referring to, which is that skeletally, there's a lot more sort of skeletally unwell people.

Yeah.