New Video from David Reich

[AimSmall]

David Reich – How One Small Tribe Conquered the World 70,000 Years Ago

https://www.youtube.com/watch?v=Uj6skZIxPuI

"Human history has been again and again a story of one group figuring ‘something’ out, and then basically wiping everyone else out.

From the tribe of 1k-10k modern humans who killed off all the other human species 70,000 years ago, to the Yamnaya steppe nomads 5,000 who killed off 90+% of (then) Europeans and also destroyed the Indus Valley Civilization.

So much of what we thought we knew about human history is turning out to be wrong, from the ‘Out of Africa’ theory to the evolution of language, and this is all thanks to the research from David Reich’s lab."

TRANSCRIPT: https://www.dwarkeshpatel.com/p/david-reich

[AimSmall]

But what's become very clear in an important series of papers since that time is that there are exceptions to this. One exception is the mitochondrial sequence, what you get from your mother and what she gets from her mother and so on. The shared ancestor there between Neanderthals and modern humans is only maybe 300,000-400,000 years ago, which is after the split that's well-estimated from the whole genome. We've also learned this is true for the Y chromosome, inherited from father to father. It too is only maybe 300,000 or 400,000 years separated between Neanderthals and modern humans. Like with the mitochondrial DNA, the Denisovans are much more distant, maybe 700,000 years to a million years.


So the story told by these two parts of the genome is really different from the rest of the genome and incompatible with the main story. We know from these papers that maybe a few percent, 3-8%, of Neanderthal DNA comes from a gene flow event into the ancestors of Neanderthals from the modern human lineage a few hundred thousand years ago. It's tempting to think that both the Neanderthal mitochondrial DNA and Y chromosome come from that event. But the probability of that happening by chance is only 5% squared, which is very small.

People have invoked epicycles, like natural selection for the mitochondrial DNA coming from modern humans, or natural selection coming from the Y chromosome coming from modern humans, somehow being more advantageous and pushed up in frequency. But that would have to happen on both these parts of the genome to produce this pattern. It just seems surprising. 
What's been put together is a complicated model and epicycle ideas like natural selection to make it work. It's not impossible. It may be the case. But one wonders whether profoundly different models might actually explain the data. That’s something we and others have been thinking about. Can there be other models? 

One example we've been playing with is one where there’s much more DNA in Neanderthals from modern humans than the 3-5% estimated. We can get such models to fit but here it’s 30% or 50% or 70%. In that view, Neanderthals and Denisovans are not sisters. In fact, modern humans and Neanderthals are just as qualified to be sisters as Neanderthals and Denisovans. In that case, maybe it's not clear what's modern and what's archaic. Are modern humans archaic? Are modern humans modern? Are Neanderthals archaic? Neanderthals are modern. 

Bolding done by me... thought that was very interesting.

[pelop]

It was a very interesting interview but unlike what the youtuber implies, Reich never said that the "Out of Africa" theory is wrong. "Out of Africa" doesn't mean there were no archaic humans living outside of Africa or that some ancestors of modern humans didn't live at some point outside of Africa, it specifically refers to the recent African origin of modern humans.

[ArmandoR1b]

I'm enjoying the video

[AimSmall]

I thought it was a great two hours.