David Reich

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.

They probably are, but maybe you could argue they knew about each other somehow.

Or the Papuan one, maybe you could argue they somehow knew about what was going on in other parts of the world, but probably didn't.

But certainly the Americas one was isolated.

And suddenly, for the first time, you have these independent evolutions of full-blown agriculture at the same time in many places in the world after the Ice Age.

This makes you think that it's somehow deterministic, that somehow some kind of setup of characteristics at this time causes this to happen.

And why doesn't it happen at the previous period of stable climate before the last ice age?

Some people say, well, maybe it was actually not as good as the last 10,000 years.