Origin of Tibetans (Wang et al. 2011)

The correspondence of language-ethnic affiliation with genomic data is quite striking as can be seen in the neighbor-joining tree (bottom). From the paper:

The migration routes of the Chinese population as a single group have been outlined based on Y chromosome haplotype distributions. After the ancestors of Sino-Tibetans reached the upper and middle Yellow River basin, they divided into two subgroups: Proto-Tibeto-Burman and Proto-Chinese [2]. These two subgroups were similar to the two ancestral components of EA populations at K = 2 (Figure S1B). The ancestral component which was dominant in Tibetan and Yi arose from the Proto-Tibeto-Burman subgroup, which marched on to south-west China and later, through one of its branches, became the ancestor of modern Tibetans. Proto-Tibeto-Burmans also spread over the Hengduan Mountains where the Yi have lived for hundreds of generations [28]. Taking the optimal living condition and the easiest migration route into account, we favor the single-route hypothesis; it is more likely that their migration into the Tibetan Plateau through the Hengduan Mountain valleys occurred after Tibetan ancestors separated from the other Proto-Tibeto-Burman groups and diverged to form the modern Tibetan population.

I recently uncovered a genetic component specific to Altaic populations, and this paper shows that within the Sino-Tibetan group, a component centered on Tibeto-Burmans can be uncovered as well. Genomics is already contributing greatly to our understanding of ancient languages, and it is perhaps time for geneticists to use their tools in order to date the breakup of these language groups, providing important new data on which to base linguistic theories.

PLoS ONE 6(2): e17002. doi:10.1371/journal.pone.0017002

On the Origin of Tibetans and Their Genetic Basis in Adapting High-Altitude Environments

Binbin Wang et al.

Since their arrival in the Tibetan Plateau during the Neolithic Age, Tibetans have been well-adapted to extreme environmental conditions and possess genetic variation that reflect their living environment and migratory history. To investigate the origin of Tibetans and the genetic basis of adaptation in a rigorous environment, we genotyped 30 Tibetan individuals with more than one million SNP markers. Our findings suggested that Tibetans, together with the Yi people, were descendants of Tibeto-Burmans who diverged from ancient settlers of East Asia. The valleys of the Hengduan Mountain range may be a major migration route. We also identified a set of positively-selected genes that belong to functional classes of the embryonic, female gonad, and blood vessel developments, as well as response to hypoxia. Most of these genes were highly correlated with population-specific and beneficial phenotypes, such as high infant survival rate and the absence of chronic mountain sickness.

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