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There were possibly late archaic introgression events in Eurasia

A few weeks ago I posted on the strong likelihood that there were at least two Denisovan admixture events in Eurasia into modern humans. That’s probably the floor, not the ceiling. We have an Altai Denisovan genome, but the proportion is so low in most of South and Southeast Asia I don’t think we have a good grasp of how that component differs from the Oceanian fraction, which is much higher.

At the AAPA meeting last week I noticed something strange in one of the presentations: introgressed Denisovan variants which were present among East Asian populations, but lacking elsewhere. The fractions were not >50%, but they were >10%. The Denisovan variants were nearly absent outside of this core zone of East Asians.

There are two possible reasons for this distribution. One reason is that Denisovan variants were segregating in East Asians for thousands of years, and a common bottleneck, or, more likely selection, drove them up in frequency. Another, not exclusive, explanation is that admixture occurred in East Asia relatively late. The Denisovan signature is totally absent in the New World. Either that’s selection or drift eliminating variation, or, it’s the fact that this admixture event happened in East Asia less than about 30,000 years ago when Native American populations’ East Asian-like source population began to divergence from that of East Asians.

One thing that we know from paleontology is that species exist before the remains we find, and persist after the remains we find. It’s quite possible that small relic populations of Denisovans persisted for thousands of years after modern humans came to dominate the East Asian landscape.

3 thoughts on “There were possibly late archaic introgression events in Eurasia

  1. How likely is it that there was hybridization between homo erectus and the Denisovans and/or between homo sapiens and homo Erectus?
    The Ngandong skulls look more modern, and there is genetic evidence of introgression from a more diverged hominin in Denisovan DNA.
    It’s hard to know where to look next, I get the feeling that a lot of the really interesting stuff has been washed out by very recent replacement. Maybe the best evidence will come from barely prehistoric DNA where refugia allowed some modern populations with exotic lineages to survive.

  2. The Denisovans probably lived very high in the mountains, which explains the known ‘high altitude’ genes that made their way into Tibetans.

    Before modern humans acquired those genes, it would have been all theirs.

  3. My 2 cents: as Neanderthals/Denisovans and moderns seem to have been on the cusp of speciation, with reduced male fertility in hybrids, interbreeding between erectines and moderns seems to me like a long shot.

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