David Reich

It's from this population that forms the Middle Stone Age.

And they mix with local groups, and who knows where they are?

Southern Africa, Western Africa, Central Africa, Eastern Africa.

We don't have any ancient DNA.

But this is a very rich environment.

People have been living there for seven million years at least.

And there would have been different groups of people everywhere.

Probably it's not just two groups.

It's probably more groups.

I think the important theme here is there's evidence of substructure that's well more than a million years ago

And this place would have been a landscape full of archaic humans that would have been differently related to these expanding people and would have admixed with them when they came through.

Well, it spreads through genes, too.

If you look at Yamnaya in India, there's almost no Yamnaya ancestry in India.

I mean, it's just diluted, diluted, diluted down.

As modern, as Yamnaya expanded into Central Asia, you know, like expands into Europe, it makes the corded wear.

There's a 25% dilution.

It expands back across Central Asia.

It goes through the Hindu Kush.

You know, it gets into Northern South Asia.

It mixes more with local people.