David Reich

20% Irish and 30% Chinese or whatever it is, and so on and so forth.

And what they're referring to is roll back 20 or 30 generations, where are your ancestors scattered in proportions?

But then if you roll back 3000 generations, there's some in East Africa and some Neanderthals, right?

So what you can actually do is for any one group of people or any one person, there's different time slices that matter.

30 generations ago, you get the 23andMe output.

3,000 generations ago, you get the proportion of your ancestors who are Neanderthals or not Neanderthals or Denisovans or something like that, if you're from one of the many populations around the world that live in Denisovans.

If you are any population, going back further in time, presumably there's something similar happening, where mostly in Africa, but possibly outside of Africa 300,000 years ago, people's ancestors will be coming from different places.

It's very...

plausible that people's ancestors are not all in Ethiopia at 200,000 years ago, that in fact, some of them are in North Africa, some of them are maybe in West Africa, some of them are in South Africa, some of them are in Eurasia, and that actually appreciable fractions are in each place, and that that braid and that trellis is coming together again and again over time.

As you move further back, they'll collapse, some will go extinct, some will reappear, some will reemerge.

And at any one point, there's never a singularity.

79 AD.

Yeah, I don't even, there's like many things in this area, but I'll give you, I'll give you the simple one and then I'll give you,

I probably should give you a single answer.

But I think that the basic answer is what we need is DNA from Africa.

So we need DNA, old DNA from 50,000 years ago, 100,000 years ago, 200,000 years ago from all over Africa.

Because it's super clear that our lineage is complicated within Africa.

There's archaic forms in the archaeological record.

And modern human data is extremely substructured with evidence of having come together from many different lineages, which must have been different archaic forms in Africa.

and contributing to people living today.