David Reich

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.

Well, maybe the arrival of the Beaker phenomenon, which happens about 4,500 years ago, maybe it's not an invasion, maybe it's a kind of peaceful event, maybe the previous people

The reason we're seeing such a disruption is the previous people, we know they cremated their dead and the Beaker people buried their dead.

So it looks like a much more abrupt change than it did.

Maybe what happens in Iberia when there's a 40% arrival of these foreigners from the East and 60% local people, but the Y chromosomes are completely replaced.

So the local men don't sort of contribute their DNA to local later populations.

It looks to you, it looks somehow like that must be extremely disruptive to the local male population.

But people are saying, well, maybe this is female mate choice.

Maybe this is somehow kind of not what you think it is.

Maybe it's not what happened 4,000 years later amongst the descendant of the Iberians in the Americas, where today in Colombia, 95% of the Y chromosomes are European, 95% of the mitochondrial DNAs are Native American.

We know what happened there.

It wasn't friendly.

It wasn't peaceful.

It wasn't nice.