Our ancient relatives, Neanderthals and Denisovans not only introgressed with humans, they also admixed with an archaic hominin population, and passed some of the archaic's DNA to us!
A paper (Mapping gene flow between ancient hominins through demography-aware inference of the ancestral recombination graph, Melissa J. Hubisz, Amy L. Williams, Adam Siepel, BioRxiv, June 30, 2019. doi: https://doi.org/10.1101/687368), used its computer simulation model (ARGweaver-D) to find:
" We identify 1% of the Denisovan genome as introgressed from a super-archaic hominin [Sup], which is double our estimated false positive rate for this event. The fact that we found much less than the ∼6% estimated by previous methods might suggest that the super-archaic divergence time is closer to 1Mya, since we would expect to have more power with a higher divergence time. Still, this analysis resulted in 27Mb of sequence that may represent a partial genome sequence from a new archaic hominin. ARGweaver-D also predicted a small fraction of the Neanderthal genomes as introgressed from a super-archaic hominin (0.75% for Altai and 0.70% for Vindija). These amounts are only slightly above the estimated false positive rates (0.65%), and the Sup→Nea event has not been previously hypothesized."
It adds more information on Denisovan admixture with Super-archaics:
"ARGweaver-D also identified 1% of the Denisovan genome as introgressed from a super-archaic hominin. Previous studies have estimated the total amount of Sup→Den as roughly 6% [8], but this is the first study to be able to identify specific introgressed regions. The fact that we only find a small fraction of the total amount suggests that the introgressing population was not too highly diverged from other hominins; this low power is much more consistent with a divergence time of 1Mya than 1.5Mya. Still, we report 27Mb of putative super-archaic sequence from this previously-unsequenced hominin, and we note that 15% of these regions have been passed on to modern humans through Den→Hum introgression. "
And also mentions Africans admixin with the super-archaic hominins but found it hard to track due to the large size of the "recipient" population (Africans):
"There have been several studies suggesting super-archaic introgression into various African poulations. However, ARGweaver-D only detected a small amount of Sup→Afr introgression, which was somewhat lower than our estimated false positive rate. One aspect to note here is that the power to identify introgression from an unsequenced population is highly dependent on the population size of the recipient population..."
The interesting find is that Neanderthals received an imput from humans in an admixture event some 300 kya.:
" We identify 3% of the Neanderthal genome that is putatively introgressed from ancient humans, and estimate that the gene flow occurred between 200-300kya."
Where did this event take place? Not in Africa because there is no Neanderthal DNA there. So this means ancient humans left Africa and bred with Neanderthals in Asia 200-300,000 years ago, long before any currently accepted Out Of Africa migration date.
Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia Copyright 2009-2019 by Austin Whittall ©
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