David Reich

It's tempting to think evolution has stopped from one perspective because there's so little fixed differences.

But on the other hand,

Somehow it looks, if you look in the last 10,000 years in West Eurasian DNA, which we're doing now, it looks like a lot of change is happening.

So it's a very confusing situation.

It feels like we don't really understand what's going on, but there's a lot to learn.

So we're working right now on a study which is documenting changes over the last 10,000 years in Europe and Western Eurasia, based on tracing changes in about 8,500 high-quality DNA sequences from people from this period that have been collectively accumulated by us and others.

So we've been working very hard at this, led by Ali Akbari in my group.

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.