Genetic Origins and Adaptive Evolution of the Deng People on the Tibetan Plateau

The Tibetan Plateau is populated by diverse ethnic groups, but most of them are underrepresented in genomics studies compared with the Tibetans (TIB). Here, to gain further insight into the genetic diversity and evolutionary history of the people living in the Tibetan Plateau, we sequenced 54 whole genomes of the Deng people with high coverage (30-60x) and analyzed the data together with that of TIB and Sherpas, as well as 968 ancient Asian genomes and available archaic and modern human data. We identified 17.74 million novel single-nucleotide variants from the newly sequenced genomes, although the Deng people showed reduced genomic diversity and a relatively small effective population size. Compared with the other Tibetan highlander groups which are highly admixed, the Deng people are dominated by a sole ancestry that could be traced to some ancient northern East Asian populations. The divergence between Deng and Tibetan people (similar to 4,700-7,200 years) was more recent than that between highlanders and the Han Chinese (Deng-HAN, similar to 9,000-14,000 years; TIB-HAN, 7,200-10,000 years). Adaptive genetic variants (AGVs) identified in the Deng are only partially shared with those previously reported in the TIB like HLA-DQB1, whereas others like KLHL12 were not reported in TIB. In contrast, the top candidate genes harboring AGVs as previously identified in TIB, like EPAS1 and EGLN1, do not show strong positive selection signals in Deng. Interestingly, Deng also showed a different archaic introgression scenario from that observed in the TIB. Our results suggest that convergent adaptation might be prevalent on the Tibetan Plateau.

Automated summary

By sequencing and analyzing the genomes of Deng people living on the Tibetan Plateau, it was found that they have reduced genomic diversity compared to Tibetans and have a sole ancestry traced back to ancient northern East Asian populations. The divergence between Deng and Tibetan people is more recent than that between highlanders and the Han Chinese. Adaptive genetic variants in Deng are partially different from those in Tibetans, suggesting convergent adaptation may be prevalent on the Tibetan Plateau.