David Reich

And the whole thing is not obviously very, very different.

So you can actually reassemble the whole model in a new way without doing it from the ground up or from the simple model up, but in fact, thinking about it again and seeing if it can be all related in new ways.

And in fact, it might be actually quite different in the way that I just described.

Even that's not clear, but probably such a thing would have occurred somewhere in the Near East or in Western Eurasia somehow.

And it's not even clear where the modern human lineage at that time was residing.

So probably the modern human lineage was leading to the great majority of the ancestors of people today was in Sub-Saharan Africa for the last 500,000 years at least, and maybe might be much more.

Certainly, our main lineage was in Africa probably 3 million, 5 million, 7 million years ago.

But in a period between about 2 million to 500,000 years ago, I think it's not at all clear where the main ancestors leading to modern humans were.

There were humans throughout many parts of Eurasia and throughout many parts of Africa with...

a parallel increase in brain size and not obviously closer ancestrality to modern humans in one place than in the other.

It's not clear where the main lineages were.

Maybe they were in both places and mixed to form the lineages that gave rise to people today.

So I think there's been an assumption where Africa's been at the center of everything.

Yeah.

for many, many millions of years.

And certainly it's been absolutely central at many periods in human history.

But in this key period when modern humans develop from Homo habilis and Homo erectus all the way to Homo heidelbergensis and the shared ancestor of Neanderthals, modern humans, and Denisovans, that time period, which is when a lot of important change happens, it's not clear, as I understand it, based on the archaeology and also certainly based on the genetics where that occurred.

Well, the simplest version of this is that the main lineage leading to modern humans is in Africa at this point.

And Africa, as I understand it from talking with the archaeologists and the climatologists, is that Africa and the Near East are continuous ecological spaces at certain periods of time.

And so there's no difference between what's now the Near East and Africa.