David Reich

And then there's before that, there's a few tens of thousands of years of warming.

And that's when we sample...

the Neanderthals, the late Neanderthals from.

And then before that, there's another stage of cooling.

And then before that, another stage of warming.

So this is marine isotope stage one, three, five, seven, nine are the warm periods.

We're in one now.

And marine stage two, four, six, eight, and so on are the ice ages.

So the last glacial maximum was marine isotope stage two.

I think we would.

I think nobody has found... I mean, there's very sophisticated human burials in Europe and Africa and East Asia and different parts of South Asia and Eurasia and so on.

Australia in the last, you know, in the marine isotope stage three, in the last period of warming.

And...

you know, burials full of beads, burials full of symbolic behavior.

Maybe you interpret this as civilization, but extensive settled societies you don't see.

The entire human lineage is... I think that the sort of lesson from ancient DNA and the genome revolution has been that anyone in the world is the result of recurrent mixture again and again in the past.

So you might think that the last 500 years are unusual periods of history with the people of African and European and

Native American ancestry coming together in the Americas, and that this is unusual because of transatlantic travel, but almost every group in the world is the result of many mixture events as profound as these on many timescales.

So South Asians are the result of mixture between groups very different from each other, as different as Europeans and East Asians.

four to three to 2,000 years ago, coming together and then crystallizing into a relative lack of mixture.