Recent analysis of DNA extracted from two Eurasian forms of archaic human show that more genetic variants are shared with humans currently living in Eurasia than with anatomically modern humans in sub-Saharan Africa. While these genome-wide average measures of genetic similarity are consistent with the hypothesis of archaic admixture in Eurasia, analyses of individual loci exhibiting the signal of archaic introgression are needed to test alternative hypotheses and investigate the admixture process. Here, we provide a detailed sequence analysis of the innate immune gene, OAS1, a locus with a divergent Melanesian haplotype that is very similar to the Denisova sequence from the Altai region of Siberia. We re-sequenced a 7 kb region encompassing the OAS1 gene in 88 individuals from 6 Old World populations (San, Biaka, Mandenka, French Basque, Han Chinese, and Papua New Guineans) and discovered previously unknown and ancient genetic variation. The 5′ region of this gene has unusual patterns of diversity, including 1) higher levels of nucleotide diversity in Papuans than in sub-Saharan Africans, 2) very deep ancestry with an estimated time to the most recent common ancestor of >3 million years, and 3) a basal branching pattern with Papuan individuals on either side of the rooted network. A global geographic survey of >1500 individuals showed that the divergent Papuan haplotype is nearly restricted to populations from eastern Indonesia and Melanesia. Polymorphic sites within this haplotype are shared with the draft Denisova genome over a span of ∼90 kb and are associated with an extended block of linkage disequilibrium, supporting the hypothesis that this haplotype introgressed from an archaic source that likely lived in Eurasia.
Got a copy of the paper (thanks again) and I would say that these two figures are of special interest:
|Fig. 2 – Median joining network of OAS 1 haplotypes|
|Fig. 3 Geographic distribution of the deep lineage in A) Old World populations and B)
South East Asians and Oceanians.
I find particularly notable that the haplotype has been found at very low frequencies in South Asia and nowhere else West of Wallace Line. It can be backflow but may also be indicator about the possible location of the admixture event.
Certainly nothing seems to suggests in these or other maps (1, 2) of “Denisovan” admixture that the episode could have happened in Altai or nearby areas as some readers, stubborn proponents of obsolete migration models, have insisted on. Instead all the evidence suggests that the admixture episode happened in SE or otherwise Tropical Asia, whether deep in Indonesia or more towards the mainland is debatable indeed.
- Neanderthal gene flow found in modern humans (on Green 2010)
- Exploring the Neanderthal admixture episode (version 1)
- Denisova hominins, Neanderthals, Melanesians and so on… (on Reich 2010)
- Explaining ‘Denisovan’ and also ‘Neanderthal’ admixture: the simplest scenario (where I first hypothesize that H. erectus and also maybe a relative of Neanderthals like the Hathnora hominin, could be the actual culprits).
- Is X-DNA lineage Neanderthal?
- Denisovan admixture widespread beyond Wallace Line, non-existent elsewhere – but then:
- Minimal Denisovan admixture in SE Asians.
- ‘Denisovan’ admixture may actually be from H. erectus.