David Reich

will unseat these people, disrupt these people, especially after a period of stasis, after a period of, especially once, sorry, especially once when you have farmers who are densely settled and how could these be pastoralists coming from somewhere else?

They're not as dense on the ground.

In India today, the British were sort of in control, the Mughals were in control for hundreds of years, but made hardly any demographic impact.

How could people from outside with less density make much of a demographic impact?

But then you look at the genetic data, and there's a 50%, 70%, 90% population disruption.

You take the DNA from people after these events, and almost all their ancestors are from far Eastern Europe, right across most of Europe.

And so the DNA proved that that idea was wrong.

It was very disruptive.

So the question that you had is, what does it look like on the ground?

And so the DNA results was extremely disruptive to people in archaeology who had made these arguments that change wasn't possible in this very, that large-scale migration, large-scale disruption probably didn't occur in the past.

And so it was a real challenge.

It was a real challenge to our understanding of prehistory.

It was sort of a case example, a prime example that's been important for me in showing that we really don't know what the past was like until we actually

look at it and have hard data telling us what it's like.

Our guesses, our models, including many of mine, are likely to be wrong because we can see that, because when we have hard data, we're surprised.

I'm sorry for that long preamble.

So when...

What's happened in the last few years is there's been something of a reconciliation after the book.

Archaeology is trying to reconcile itself with the DNA data, and it's arguing about the subtlety of these interaction events.

So people talk about what's happened in Britain, for example.