David Reich

But maybe what happened in Iberia 4,000 years ago amongst these ancestors of people was much more peaceful, was much more calm.

If you look at detail in Iberia, what you see is the period of this change is actually over 500 years.

But if you look at a microscale, now that we have better data, it's immediate each place.

So in southern Spain, it's very fast.

And then in central Spain, it's a little later, but very fast.

And so actually, there's these rapid changes occurring in one place or another.

People thought in Britain, maybe this was actually a slow process.

But we now have data not yet published from the Netherlands, which is clearly the same population of Beaker people that's spreading in Britain.

And there it's very disruptive.

And you actually have the whole series of people before and after.

You see that earlier Corded Ware people are local, which is actually very unusual for Corded Ware.

They're actually local people adopting the religion of the Corded Ware, but mostly local ancestry.

And then the Beaker arrival is incredible disruption.

There's almost no continuity, very little continuity.

So probably what's happening with the Beaker individuals is one way or the other, you have some kind of people who expand demographically

and displaced people somehow, rapidly displaced people over a period of well less than a century.

So we don't know.

And I think there's debates even about that.

I think one example I've heard archaeologists I work with think about is...

is the Comanche in the US Southwest, where it's another horse-based expanding group.