  The origin and diversification of Sino-Tibetan populations have been a
long-standing hot debate. However, the limited genetic information of Tibetan
populations keeps this topic far from clear. In the present study, we genotyped
15 forensic autosomal STRs from 803 unrelated Tibetan individuals from Gansu
Province (635 from Gannan and 168 from Tianzhu). We combined these data with
published dataset to infer a detailed population affinities and admixture of
Sino-Tibetan populations. Our results revealed that the genetic structure of
Sino-Tibetan populations was strongly correlated with linguistic affiliations.
Although the among-population variances are relatively small, the genetic
components for Tibetan, Lolo-Burmese, and Han Chinese were quite distinctive,
especially for the Deng, Nu, and Derung of Lolo-Burmese. Southern indigenous
populations, such as Tai-Kadai and Hmong-Mien populations might have made
substantial genetic contribution to Han Chinese and Altaic populations, but not
to Tibetans. Likewise, Han Chinese but not Tibetan shared very similar genetic
makeups with Altaic populations, which did not support the North Asian origin
of Tibetan populations. The dataset generated here are also valuable for
forensic identification.
