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Monday, December 22, 2014

Ancient East European and West Asian admixture deep in Siberia

The full mito sequences from this new Derenko at al. study should come in very handy when many more ancient genomes from across North Eurasia are published. The paper is open access, but here are a few excerpts anyway:

Although the genetic heritage of aboriginal Siberians is mostly of eastern Asian ancestry, a substantial western Eurasian component is observed in the majority of northern Asian populations. Traces of at least two migrations into southern Siberia, one from eastern Europe and the other from western Asia/the Caucasus have been detected previously in mitochondrial gene pools of modern Siberians.

We report here 166 new complete mitochondrial DNA (mtDNA) sequences that allow us to expand and re-analyze the available data sets of western Eurasian lineages found in northern Asian populations, define the phylogenetic status of Siberian-specific subclades and search for links between mtDNA haplotypes/subclades and events of human migrations. From a survey of 158 western Eurasian mtDNA genomes found in Siberia we estimate that nearly 40% of them most likely have western Asian and another 29% European ancestry. It is striking that 65 of northern Asian mitogenomes, i.e. ~41%, fall into 19 branches and subclades which can be considered as Siberian-specific being found so far only in Siberian populations. From the coalescence analysis it is evident that the sequence divergence of Siberian-specific subclades was relatively small, corresponding to only 0.6-9.5 kya (using the complete mtDNA rate) and 1–6 kya (coding region rate).


Overall, the phylogeographic analysis strongly implies that the western Eurasian founders, giving rise to Siberian specific subclades, trace their ancestry only to the early and mid-Holocene, though some of genetic lineages may trace their ancestry back to the end of LGM. Importantly, we have not found the modern northern Asians to have western Eurasian genetic components of sufficient antiquity to indicate traces of pre-LGM expansions, that originated from the Upper Paleolithic industries present both in the southern Siberia and Siberian Arctic, and that date back to ~30 kya, well before the LGM [43]–[45]. Apparently, the Upper Paleolithic population of northern Asia, whose western Eurasian ancestry was approved recently by complete genome sequencing of 24 kya-old individual from Mal’ta and 17 kya-old individual from Afontova Gora in south-central Siberia, did not leave a genetic mark on the female lineages of modern Siberians. It is probable that the initial population expansion in the southern Siberia region involved maternal lineages other than present now, or that there was a substantial gene flow into the region after the LGM, most probably from eastern Asian sources as have been suggested by Raghavan et al. [7].


Derenko et al.: Western Eurasian ancestry in modern Siberians based on mitogenomic data. BMC Evolutionary Biology 2014 14:217. doi:10.1186/s12862-014-0217-9