AI outputs that humans have a ‘ghost’ ancestor

#1
https://geneticliteracyproject.org/2019/...thinks-so/

EXCERPT: . . . All non-Africans today have a small percentage of Neanderthal DNA, while Denisovan DNA is particularly common in Asian and Oceanian populations. [...] The idea of a “ghost population” — an unknown species inferred to exist through statistical techniques — had been postulated to account for archaic sections of the human genome that do not match Neanderthal or Denisovan DNA.

This third archaic species was identified using “a demographic model based on deep learning in an Approximate Bayesian Computation framework,” the researchers wrote in their article published in Nature Communications last month. “We have an overwhelming support for the existence of a third extinct branch of the Neanderthal-Denisovan clade,” they said.

The species appears to be responsible for a third unique introgression (the introduction of genes from one species to another via crossbreeding) into the genome of anatomically modern humans, with the first two introgressions resulting from modern humans mating with Neanderthals and Denisovans. The third extinct species is likely a hybrid or close relative of Neanderthals and Denisovans that crossbred with “Out of Africa” modern humans in Asia. (MORE)
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#2
Humans have ghosts as ancestors?? I thought that was only true for MR.

Seriously though, I wouldn't be surprised. My suspicion is that the evolution of human beings was hugely complex. (That's probably true of many species.)

I'm skeptical if anatomically modern humans left Africa all at once in one giant exodus, and then simply drove all the earlier hominins already in Eurasia to extinction, replacing them with no remainder.

I'm more inclined to think that a variety of sorts of hominins kind of leaked out of Africa in small bands over a long period of time (much of human evolution), spreading all over Eurasia where they developed into a variety of variants. There were the early Homo erectus varieties like Peking and Java man, there were the rather late Flores Island Hobbits and the better known later varieties like the Neanderthals and Denisovans. There are probably more that we don't even know about. So I'm not surprised to see evidence that there were.

And how these variants interacted when they came into contact is probably complex too. Interbreeding certainly seems to have happened. Not sure how prevalent it was or how much social taboo there was against it. It may have varied.

So rather than all modern humans being the result of one out-of-Africa surge less than 100,000 years ago, we may be hybrids with very complicated ancestries. I don't know that, but I suspect it's true.
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