Harvard geneticist David Reich gave a long interview which can be seen in video online here It includes a transcript from where I extracted the text that I share below.
Reich, born in 1974 is Professor of Genetics, Harvard Medical School and Professor of Human Evolutionary Biology who has specialized in population genetics and the genetics of ancient humans. His laboratory has sequenced the genes of over 16,000 people. He is a leader in this field so his opinion about Out of Africa and diversity, population structure and the braids that linke Neanderthals, Denisovans, and modern humans are indeed interesting.
Out of Africa needs a "Copernican Readjustment"
I liked the comparison of a Ptolemaic vs. a Copernican viewpoint for the Out of Africa theory. Reich says (talking about Neanderthals, Denisovans and modern humans) the following:
" When these lineages interacted with each other at different periods of time. But the standard model we have right now is really almost hard to believe. So the standard model right now is that modern humans are a distant cousin of Neanderthals and Denisovans, who are most closely related. Neanderthals and Denisovans stemmed from a common ancestor maybe half a million years ago, which separated earlier from the ancestors of modern humans. But actually, maybe there's some alternative way of thinking about what happened that can really change our vision of the relationships amongst these groups and make it sort of the Copernican readjustment where we say, well, maybe, maybe the maybe the solar system revolves around the sun, and the Earth is a satellite of that. And maybe, maybe that's how it looks. And so I kind of feel that we're missing a trick and that there's something there, and that maybe if we come up with a different model, it will be much more plausible."
On Out of Africa, replacement, and our origins
In another podcast from 2024 (Online here - Dwarkesh Podcast) Reich has some interesting comments (I give the approx. time he says them, also see the transcript):
- Time: 2:05 min. He says the model is implausible, and mentions the Copernican analogy.
- Time: 5:20 min. "Profoundly different models may actually explain the data" in a more plausible manner. At 8 min he adds that each new study is accreted onto the "Standard" (orthodox) model like patches.
- Time: 9:30 min. "in a period of 2 million to 500 thousand years ago I think it is not at all clear where the main ancestors leading to modern humans were, there were humans through many parts of Eurasia and many parts of Africa... I think there's been an assumption where Africa has been at the center of everything."
- Time: 13:00 min. Several hundreds of thousands of years ago a lineage gets into the Middle East and mixes there with the ancestors of Neanderthals.
- Time: 14:00 min. In Africa there were hundreds of small populations with low diversity, almost going extinct, but seen as a whole, their added diversity, and random occasional admixing created the current high diversity of modern humans.
- Time: 52:00 min. Humans changed a lot over the past 2 million years, but then looking back at the past 200 ky, Africans, Oceanians and Eurasians are very similar, only in the past 10,000 years do we see an acceleration of evolution due to selection in Western Eurasia which is baffling: "There's a kind of disconnect... It's a very confusing situation. It feels like we don't really understand what's going on, but there's a lot to learn."
- Time: 1 h 04 min. Replacement of populations are disruptive events, when a Y-chromosome lineage is compeltely replaced by another, yet the mtDNA did not change, it means the men were wiped out and women had no choice about their mates "It wasn't friendly, peaceful, or nice."
- Time: 1h 16 min. "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?... 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... It’s not even obvious that non-Africans today are modern humans. Maybe they're Neanderthals who became modernized by waves and waves of admixture."
- Time: 1 h 26 min. "The evidence that our lineage was mostly in Africa is based on an assumption, a kind of inertial idea, that our lineage must have always been in Africa because Africa is the center of human history. But if you look at the archaeological evidence, it's not incredibly clear. If you look at the genetic evidence, we have many early branches from Eurasia and only one from Africa. You have complexity and branching in Eurasia that's sampled in the DNA record, DNA from Denisovans, DNA from unknown archaic lineages that contributed to Denisovans, Neanderthals. All of those are represented in the Eurasian record, not in the African record. Part of that is the fact that ancient DNA is preserved in Eurasia. Maybe there's a period when our lineage resides in Eurasia. It's not obviously wrong. That hypothesis is out there as a possibility."
- Time: 1 h 32 min. On what is lacking in the field: "The basic answer is that we need DNA from Africa. We need old DNA from 50,000 years ago, 100,000 years ago, 200,000 years ago, from all over Africa. Because it's super clear that our lineage is complicated within Africa. There's archaic forms in the archaeological record. Modern human data is extremely substructured, with evidence of having come together from many different lineages, which must have been different archaic forms in Africa contributing to people living today. Having that would crack our understanding of how modern human lineages braided together and relate to the other archaic lineages we have data from. That's obviously extremely helpful."
Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia Copyright 2009-2026 by Austin Whittall ©
