Razib Khan One-stop-shopping for all of my content

May 16, 2019

What might have happened to earlier modern humans

A few years ago a paper came out, Ancient gene flow from early modern humans into Eastern Neanderthals, which recorded evidence of ancestry related to modern humans which evolved in Africa in the Altai Neanderthal genome. There has also been evidence that ancestral Neanderthals had their mtDNA lineages replaced by African lineages more than 200,000 years ago. To my knowledge there isn’t much evidence of modern admixture into Denisovans…but we don’t have that many Denisovan genomes, and the ones we have are from a single location.

After thinking about it seems likely that there was a complex sequence of interactions and gene flow between structured Eurasian and African humans over the last million years. The gene flow may have occurred in pulses, and unevenly. There are some suggestive modern human sites before 60,000 years ago in parts of Asia. The timing here is important since this threshold is when modern humans as we know them really began expanding.

So this is the verbal model:

  • Several modern human populations sampled from the ancient African structured modern human population contributed genetically to different archaic Eurasians at different times
  • Some of these modern populations were the ones that left remains or tools which are identified as modern, but “too old”
  • These populations were absorbed into larger archaic Eurasian hominin populations.
  • Later, these archaic Eurasian hominins were absorbed into the last modern wave out of Africa, but their ancestry was well mixed enough into the archaics that they are seen as part of the archaic background

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