David Reich

There's Native Americans encountering Africans and Europeans as they come from the old world.

There's various other groups encountering other groups.

And you have people who have cognitively or...

culturally all the capacity to thrive in other contexts but just because of the nature of the interaction that happens one group declines demographically and one group doesn't and it's just complicated so I don't think you should conclude necessarily it's very tempting to think

that at some level it's innate, biological.

I'm not trying to be politically correct, that it's innate, some better biological hardware that makes it possible for these African lineages to spread into Eurasia.

I have no good insight into that topic.

I don't think there's very good genetic evidence or any other kind of evidence to say that that contributed in a very strong way.

I think that it's just complicated, and we certainly have many modern examples where people with better or more competitive cultural complexes encountering each other, and the ones that are more organized in a certain way sort of thrive somehow demographically more.

There's an amazing book by Kyle Harper called, I think it's called The Fate of Rome.

And it's an argument about the history.

He's a historian, a Roman historian.

And it's a history of three major plagues in the Roman period, two of which are really not even very well known, and argues that the decline of the Roman Empire is due to just weakening as the result of plagues and other climatic, biological, climatological worsening events.

Yeah.

There is a lot of reason to think that some of these events have been recurrent throughout history, and that it's not just difference between farmers and hunter-gatherers, but actually a lot of different types of interactions that are occurring.

So the example that you mentioned is something that's been a big shock from the ancient DNA revolution.

So this is now maybe eight years, nine years old.

So when the first large number of DNA sequences from people who lived five and six and 4,000 years ago in the steppe north of the Black and Caspian Seas and in Europe were being published about in 2015, this group in Denmark

led by S.K.

Willerslev and Christian Christensen and colleagues, looked at their DNA and they discovered in their sequence from the 100 or so humans they sequenced that there was also pathogen DNA.