David Reich

That's speculative.

Right, so FADS1.2, this variant, it's sort of a vegetarian slash meat-eating adaptation.

And already in work prior to this, actually, Ian Matheson, who was a former colleague who worked with me in 2015, identified this as a very strongly selected variant.

And it's actually been ancient.

You see copies in archaic humans, too.

Yeah.

One of the findings of our paper is the ABO blood system.

You get your blood typed, it's AB and O. The B variant has increased up to 10% at the expense of A. But previous work has shown that A and B were both already present in the ancestor of humans and gibbons, other apes.

And so these mutations, some of them have been going back and forth and fluctuating over time in different time periods.

But we're talking about changes in the Bronze Age.

So this TIK2 variant for tuberculosis risk, multiple sclerosis risk variant inflected and increased in frequency before the Bronze Age and then 2,000 or 3,000 years ago reversed at that period.

And there's differences in Northern Europe where this process is super strong, very strong positive selection, very strong negative selection.

And then in Southern Europe, only a little bit and not even very strong negative selection.

For hemochromatosis, which is pathogenic iron buildup,

that causes problems in Europe.

That too has reversed around this period.

In some of the complex traits that maybe we'll talk about later, these traits too have periods of intensification of natural selection.

For example, depigmentation, which is the Europeans have depigmented, gotten lighter skin over the last 10,000 years.

You can see it in our data.

The period of strongest depigmentation is between about 4,000 to 2,000 years ago.