David Reich — How one small tribe conquered the world 70,000 years ago
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Today, I have the pleasure of speaking with David Reich, who is a geneticist of ancient DNA at Harvard. And David's work and his labs work and his fields work has transformed, like really transformed our understanding of human history and human evolution. I mean, it's very fascinating stuff from many perspectives. In its own light, it's very interesting. From the perspective of AI, which I plan on asking you about, it's interesting to understand human evolution and what that implies about what the future of AI might look like. Anyways, I'll stop doing the introduction. David, we were just chat
Well, I think what's very interesting is that what we have data from now are modern humans, the sequences of people living today. We also have data from Neanderthals who are archaic humans who lived in Western Eurasia for the last couple of hundred thousand years. We have now sequences from many Neanderthals. We also have DNA from Denisovans. Denisovans are archaic humans who were discovered from the DNA, from a a a finger bone that was found in a cave in Siberia, not anticipated to be a new group of humans but were sequenced. So we have DNA from these different sources plus bits of DNA from t
The
model that we have is really a model based on accretion. So we start with the modern humans, and then we add the Neanderthals once we obtain that sequence, and we add the Denisovans. And then the model doesn't quite fit, and we add other mixture events to make the model fit. And at this point, there's a number of these mixture events that seem increasingly implausible. They feel to me a little bit like I don't know if you know the history of models of how the earth and the sun relate to each other in ancient Greek times, there's these epicycles that were attached by the Greek Hellenistic astro
Interesting. So, I mean, from your book, I remember that there are lineages of human modern humans that are over two hundred thousand years separated from other groups like the saun hunter gatherers from, everybody in Eurasia today or at least everybody descended from Eurasia. So the, then you're saying that a hundred thousand years before that is when we have a sister lineage with Neanderthals. Actually, not sure what the new findings we're finding about how closely related Neanderthals are to us and how much mitochondrial and Y chromosome DNA they share. What what model do you think is the m
I'm very agnostic. I really, really don't know.
But the ones you sorry. The ones you the models you were just talking about, it seemed sounded like you thought they were low probability. Is there one you think is, like, more
I think the models that are considered to be standard dogma are now low low probability. Yeah. So there's a standard dogma that's that's developed over an accretion of papers where the data the the history gets patched. So someone sequences a genome, someone performs an analysis, someone proves something that wasn't known before, and so we claim a mixture event we didn't know about it before, an event that we didn't know before. And that gets patched onto the current model, which is now a series of patches. And nobody has really rethought the whole thing very hard. And the whole thing is not o
Where did the gene flow between, the most recent gene flow between Neanderthals and humans? I guess not the most recent, because the most recent was sixty thousand or whatever years ago, but the one you're referring to here. Physically did that happen?
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