David Reich

It's really hard to imagine that people have bacteria in their blood and they're not dying of these things.

It doesn't seem that people are ignoring, people are selectively picking tombs.

These are tombs that are buried properly.

They're not grave pits.

So the implication seems to be this one agent that we happen to be able to detect is killing a very large fraction of people in Western Eurasia over this period.

So what's the implication of that?

One thing is that maybe it seems to be coming from steppe rodents, probably.

And so maybe the people on the steppe are somewhat more, I mean, they're still dying of it, but somewhat more protected of it than it spreads into farming Europe maybe 5,000 years ago, which is when we start to see it.

And maybe this results in disorganization of the population, giving such high rate of death.

And maybe it creates a type of situation that the Europeans encountered when they got to the Americas, where...

societies were disrupted.

So, you know, in the last few years we had COVID-19 that killed a half percent of the world population or something like that.

And it was so disruptive.

So if this thing is killing a third of people or half of people, you know, randomly

randomly killing people with cultural knowledge, randomly ripping into structures like in, I don't know, was it Montezuma died or one of his parents resulting in civil wars in the Inca when the Europeans encountered them, just disrupting the cultures that were there.

Maybe this would have created a situation where

there was disruption in the old ways of life and maybe combined with other things or even just by itself could have created an opportunity for people to move in from elsewhere even though they were not as densely spread because the big observation we haven't talked about and it's something that we as an ancient DNA community have been looking into again and again now

and keep making progress on, is that about 5,000 to 4,500 years ago in Europe, there's a radical transformation in the ancestry of Europeans.

An example of this is what happens in Britain.

So about 4,500 years ago, the farmers who are there, they arrived there 6,000 years ago, they build Stonehenge, the last big stones of Stonehenge go up 4,500 years ago, and then within 100 years, 90% of them are gone.