David Reich

There's so many of them that over time it stays Neanderthal, stays local, but it just becomes, over time, more and more modern human, and eventually it gets taken over from the inside by modern human ancestry.

This is what happens to Northern European hunter-gatherers.

They become farmer over time, but they're intact on the male line.

And culturally, they stay on the male line intact.

And so I'm not trying to be politically correct.

I'm just saying that you can actually have scenarios where this happens.

So for example, in elephants, if you look in forest elephants, which are the smaller of the two species of elephants in Africa, they're very matrilocal.

They have these female lines that are very intact over a long period of time.

And if you look at these, sorry, savanna elephants, which are the bigger elephants in Eastern and Southern Africa, they have savanna elephant DNA overall, but their mitochondrial sequences are forest elephant, which are the smaller West African elephants.

And the interpretation of this is that you just have waves of waves of dominant male bulls from the savanna coming into populations and eventually just replacing all of the genome in waves and waves of waves of an intact forest population.

And so all that's left is the mitochondrial sequence, which is passed in the maternal line.

It's not even obvious that non-Africans today are modern humans.

They're just, maybe they're Neanderthals who became modernized by waves and waves of admixture.

I don't know.

I mean, it's very speculative, but I'm very tempted to think that there's so many of these groups that some of them would eventually have gone down this route.

And one example of this that's...

that's interesting to think about is the parallel development of agriculture and the Holocene in different parts of the world.

So you have in the Americas what's almost certainly a completely independent development of agriculture 9,000, 8,000 years ago.

From that in Eurasia, you can argue whether the East Asian and...

Near Eastern developments are different.