he 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 . 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 . 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.
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.
I do not have a whole lot to say about this, but previous linguistic evidence always showed a connection between the Tibetan Plateau and Myanmar (Burma), or at least some populations there. At some point all they link back with Han Chinese as well, but it seems the connection between the Yi and Tibetans is more recent.
The genetic charts below show some type of ancient relationship (or maybe not so ancient) between the Tibetans, Yi, and Turko-Mongol groups, that is not shared in as large an amount with the Han Chinese sampled (Han are a big group, I would like to see it broken out BY "North Han" and "South Han")
Here is also a nice chart:
Edited by LongMa, 03 March 2011 - 04:00 PM.