David Reich

So it ends, I mean, in the medieval one creates a lot of inflation and the serfs, as I understand it, were sort of on fixed wages.

And so they had to be paid more.

It basically inflated out their sort of seniorial responsibilities.

That's documented with kinetics.

It's estimated to be not the primary pathogen.

Okay.

But who knows?

And in any case, I mean, there's others too, right?

So some of the other plagues in the Roman Empire are definitely not Yersinia.

We have indirect information about some of these things.

So one thing that you might hope to learn about is whether our genomes reacted to the innovation of agriculture in a disrupted way.

So you might think that our genomes would have been in some kind of steady state, sort of natural selection had adapted us to the previous environments we were in.

And you might expect that in reaction to a change so economically...

dietarily, cognitively transformative as agriculture, the genome might shift in terms of how it adapts, and so you might actually see that in terms of adaptation of the genome.

You might expect to see a quickening of natural selection or a change.

I don't think we know the answer yet to whether that's occurred, although there are beginning to be hints, and we could learn that from the DNA data.

So one question is, so there's an increasing view amongst geneticists and that natural selection is...

a process where there's relatively little directional selection to adapt to new environments.

One piece of evidence connected to this is the finding that there's very few genetic changes that are 100% different in frequency between, say, Europeans and East Asians, or West Africans and Europeans, or West Africans and East Asians.

If there had been genetic variants that had had modest selective advantages, 1%, half a percent, 2%, that's actually a lot, but year by year, that had arisen, and then that's...