The Population History Of Tibet

The Sino-Tibetan languages originate in lowland northern China in the Neolithic era, and not in Tibet. 

Archeologically attested human occupation on the Tibet Plateau (TP) can be traced back to 160 thousand years ago (kya, Xiahe) via archaic people and 30~40 kya via anatomically modern human in Nwya Devu. However, the past human movements and peopling of the TP keep in its infancy in the modern/ancient DNA studies. Here, we performed the first modern/ancient genomic meta-analysis among 3,017 Paleolithic to present-day eastern Eurasian genomes (2,444 modern individuals from 183 populations (including 98 U-Tsang/Ando/Kham Tibetans) and 573 ancients (including 161 Chinese ancients first meta-analyzed here)). 

Closer genetic connection between ancient-modern highland Tibetans and lowland island/coastal Neolithic northern East Asians was identified, reflecting the main ancestry of high-altitude Tibeto-Burman speakers originated from the ancestors of Houli/Yangshao/Longshan ancients in the middle and lower Yellow River basin, consistent with the common North-China origin of Sino-Tibetan language and dispersal pattern of millet farmers. Although the shared common northern East Asian lineage between Tibetans and lowland East Asians, we still identified genetic differentiation between Highlanders and lowland northern East Asians, the former harboring more deeply diverged Hoabinhian/Onge ancestry and the latter possessing more modern Neolithic southern East Asian and Siberian ancestry, which suggested the co-existence of Paleolithic and Neolithic ancestries in modern and Neolithic East Asian Highlanders. 

Tibetans from U-Tsang/Ando/Kham Tibetan regions showed strong population stratifications consistent with their cultural backgrounds and geographic terrains (showed as barriers for human movements): stronger Chokhopani affinity in U-Tsang Tibetans, more western Eurasian ancestry in Ando and greater Neolithic southern East Asian ancestry in Kham Tibetan. Modern combined ancient genomes documented multiple waves of human migrations in TP past: the first layer of local Hunter-Gatherer mixed with Qijia Farmer arose the Chokhopani-associated Proto-Tibetan-Burman, admixture with the additional genetic materials from the western Eurasian steppe, Yellow River and Yangtze River respectively gave rise to modern Ando, U-Tsang and Kham Tibetans.

Mengge Wang, et al., "Peopling of Tibet Plateau and multiple waves of admixture of Tibetans inferred from both modern and ancient genome-wide data" bioRxiv (July 3, 2020). doi: https://doi.org/10.1101/2020.07.03.185884