Human Population Genetic History and Evolutionary Dynamics on the Eastern Tibetan Plateau.

The origins of Tibeto-Burman populations on the eastern Tibetan Plateau (TP), especially within the Tibetan-Yi Corridor, remain unresolved. We sequenced whole genomes of 293 individuals from 21 Tibeto-Burman-speaking groups and genotyped 799 individuals from 60 Sino-Tibetan-speaking groups to reconstruct regional population history. Our analyses reveal fine-scale substructure and extensive admixture along the underrepresented Tibetan-Yi and Hexi corridors, driven by gene flow from Eastern Eurasian rice/millet farmers and Western Eurasian steppe pastoralists. We estimate that Tibetans diverged from their common ancestors with Han Chinese in the early Neolithic (∼9.9 kya), followed by differentiation among Tibetan-Yi Corridor populations in the middle Neolithic (∼4.6 kya). These splits coincide with distinct cultural trajectories that produced a pronounced north-south genetic structure among Tibeto-Burman groups. QpAdm modeling indicates that northern Tibeto-Burman speakers derive most of their ancestry from Neolithic millet farmers. Along the Hexi Corridor, an essential axis of Eurasian connectivity, fine-scale analyses show a dominant legacy of millet-farming populations with additional ancestry from incoming Eurasian herders. Together, these findings clarify the settlement history of eastern TP populations and underscore the role of geographic and cultural corridors in structuring ancient intercontinental gene flow across Eurasia.