David Reich: evaluation

Transcript context

…I want to go back to what you were saying. For hundreds of thousands of years—not just with modern humans, but with even the so-called archaic humans, Neanderthals, and other species—there's been selective pressure for larger brains. This is despite the fact that they're in different parts of the world. If you're in Eurasia or if you're in sub-Saharan Africa, either way we finally got to a state where the niche we're in rewards marginal increases in intelligence and is willing to bear the cost of that and keep chugging on that variable. Do we know why that was the case? What was happening in the world? What was happening with maybe primate brains such that the selective pressure was turning towards greater intelligence? That's a super interesting question. There's a lot of insight and ideas about this topic. It's an area to which genetics right now has contributed almost nothing. I wrote this book, Who We Are and How We Got Here: Ancient DNA and the New Science of the Human Past. It's a bit of a misleading title or a kind of a bait-and-switch title. The way in which it's a bait-and-switch title is you might read it thinking you're going to learn something about how we became whatever we think is distinctive about us relative to other animals. So I try very early in the book to say that unfortunately, with the genetic data available up to this point, we don't really have very meaningful insights about what makes us distinct, how we came to be distinct from other animals. What I'm going to tell you about is how we came to be, how we are from another perspective through mixture and migration. It's very surprising how we came to be and how we are through migrations and mixtures. A lot of people used to think that we were not mixed. In fact, it's been mixture again and again in the past in many populations we didn't anticipate. Your question was about how humans evolved into a distinctive niche that includes having a strong reliance on a large brain, putting a large amount of metabolic energy into the brain, and having a brain relative to body size that is much bigger than is in the past. I have two things that are striking to me about that. One of them is that genomics actually has promise to learn about those things. We are potentially on the verge of learning a lot about those things. We just don't have important new qualitative insights about that topic right now. The other one is that the large brain was already in place prior to the separation of Neanderthals and modern humans, and maybe Denisovans as well. The common ancestors of Neanderthals and modern humans probably had a brain as large as ours. It's not obvious that there's parallel evolution in multiple parts of the world. It may be that it's a sufficiently interconnected group that it's not a parallel evolution event but a single process. I have so many questions there. When you say that there's a single interconnected population, are you referring not only to basically all of Eurasia but also Africa?…

Stored transcript either side of the excerpt. The highlighted words are the published quote; the surrounding text is unedited source, never generated.