Dwarkesh Patel: uncertainty

Transcript context

…inea and the Bismarck Archipelago. They get to Vanuatu and Fiji and Tonga and New Caledonia and Samoa about 3,000 years ago, super rapidly in the guise of something called the Lapita cultural complex. If you look at the DNA of the people from this, they're almost entirely East Asian in ancestry. They look like early Taiwanese people. Today people in Vanuatu and Fiji and Tonga and New Caledonia have only 10 percent of this DNA. So something else happened afterward. The first people are almost entirely East Asian via Taiwan and the Philippines. Then you look at later DNA from the same part and 2,500 years ago, 500 years after the initial arrival, there's mass movement of Papuans in a male-driven way from New Guinea and the Bismarck Archipelago into Vanuatu. You have people with overwhelmingly Papuan ancestry from New Guinea coming into Vanuatu. That's the origin of the ancestry that's overwhelmingly there in Vanuatu, New Caledonia today. So there's a two-step process. The initial step is East Asian ancestry and these people who invented outrigger canoe technology and long-distance sailing. Then the technology becomes adopted by Papuans, who are using this culture for the next few hundred years. We can see them trading back and forth between the Bismarck Archipelago and Vanuatu. By the end, this culture is carried out by Papuan ancestry. Males from this group then spread into New Caledonia and take local females. But the ancestry is flipped from the way that people have this cognitive bias that it should be. People think, “Oh, it should be the East Asian males somehow dominating the local females or something.” You see the reverse. This is what's going on. It's very complicated and subtle. When you actually see evidence of males and females behaving differently, it proves that there's socially asymmetric behavior of two groups as they interact. What it means is confusing. It could be female mate choice. It could be violence. It could be genocide. It could be different patterns of male and female dispersal, with groups who travel being of one sex or the other. We can look for clues in the genetic data. Certainly in concert with the archaeology, we can maybe figure out more. That's really interesting. Going back to archaic humans, we talked a lot about Neanderthals but obviously there were two different species of Denisovans. I don't know if species is the right word, but there were two different kinds of Denisovans and also the hobbits in Asia. I don't know if there are more, but we're talking about half a dozen different distinct groups and only one survives. I understand if new cultural technologies are developed by this Near East early tribe, then they expand out through Eurasia. I get that might enable them to be so dominant. What I don't understand is how none of the other ones survived, not even one tribe of Denisovans or Neanderthals or hobbits. There was no niche in which they could just fend off. Everywhere this one tribe of African humans just dominated. How did none of them survive? I don't know. It may be a numerical issue. If you look at the part of the world where we have the best data in the Holocene, the last 10,000 years, there are places of long-term survival of hunter-gatherers for a few thousand more years than elsewhere. In the Netherlands, for example, hunter-gatherers survive for several thousand more years than in the surrounding areas, probably because they're exploiting the wetlands. But they're gone soon enough, once something happens. Mammoths go extinct mostly 14,000 years ago, but they survive on Wrangel Island north of Siberia until 4000 years ago. At some point, each of these places is encountered by the spread of modern humans at high densities. The other thing is that it's not even clear to me what expansion means. If you want to make a strong argument, you might argue that non-Africans today are Neanderthals who just have waves and waves of modern humans from Africa mixing with them. Who are the ancestors? That might sound like a silly kind of philosophical statement, but genealogically… I don't know if this happened before or after my book. You probably don't know about this. There was a super interesting series of papers. They made many things clear but one of them was that actually the proportion of non-Africans ancestors who are Neanderthals is not 2%. That’s the proportion of their DNA in our genomes today if you're a non-African person. It's more like 10-20% of your ancestors are Neanderthals. What actually happened was that when Neanderthals and modern humans met and mixed, the Neanderthal DNA was not as biologically fit. The reason was that Neanderthals had lived in small populations for about half a million years since separating from modern humans—who had lived in larger populations—and had accumulated a large number, thousands of slightly bad mutations. In the mixed populations, there was selection to remove the Neanderthal ancestry. That would have happened very, very rapidly after the mixture process. There's now overwhelming evidence that that must have happened. If you actually count your ancestors, if you're of non-African descent, how many of them were Neanderthals say, 70,000 years ago, it's not going to be 2%. It's going to be 10-20%, which is a lot. Maybe the right way to think about this is that you have a population in the Near East, for example, that is just encountering waves and waves of modern humans mixing. There's so many of them that over time it stays Neanderthal. It stays local. But it just becomes, over time, more and more modern human. Eventually it gets taken over from the inside by modern human ancestry. This is what happens to northern European hunter-gatherers. They become farmer over time, but they are intact on the male line. Culturally they stay on the male line intact. I'm not trying to be politically correct, I'm just saying that you can actually have scenarios where this happens, for example in elephants.…

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