An international team, led by researchers from BGI and University of California, presented their latest significant finding that the altitude adaptation in Tibet might be caused by the introgression of DNA from extinct Denisovans or Denisovan-related individuals into humans.

This work published online in Nature sheds new light into understanding human's adaptation to diverse environments including temperature extremes, new pathogens, and high altitude. Other important collaborators of this study include the scientists from The People's Hospital of Lhasa, South China University of Technology, among others.

The evolutionary adaptations has allowed Tibetans to have no trouble living at 13,000 feet all the year round. How they can conquer the harsh environment of hypoxia is the topic attracting global scientists' attentions.

Recently, the genetic studies on Tibetans' adaptation to high altitude indicated that a hypoxia pathway gene, EPAS1, had the most extreme signature of positive selection in Tibetans, and was shown to be associated with differences in hemoglobin concentration at high altitude.

In this study, researchers re-sequenced the region around EPAS1 in 40 Tibetan and 40 Han individuals, and found this gene in Tibetans harbored a highly differentiated haplotype, which was only observed in Denisovan genome but not in the populations from worldwide, except for a single Southern Han Chinese and a single Beijing Han Chinese individual.

It was previously reported that scientists found the evidence for Denisovan admixture throughout Southeast Asia (as well as in Melanesians). Given this conclusion and their findings, researchers suggested that Tibetans' ancestors may interbred with Denisovan, which could explain why the presence of Denisovan haplotype outside Melanesia.

Moreover, this gene-flow from Denisovan to Tibetans may facilitate Tibetans to adapt the harsh high-altitude environments, which sheds new light on the gene-based study on human evolution and adaptation.

Xin Jin, Research Scientist from BGI, said, "The Denisovan-like DNA we found in the genome of Tibetans implied that the adaptation to local environments could be facilitated by gene-flow from other hominins who have been adapted to such environments. This unique finding may help us re-examine the similar fast-evolution cases in the future."

Asan Ciren, Another researcher from BGI, said, " The genetic relationship or blood relationship between modern human and archaic hominins is a hot topic of the current paleoanthropology. . The finding of Tibetans's selected EPAS1 haplotype in Denisovans not only demonstrates the possibility of ancient gene-flow from Denisovans- or -like population to ancestors of Tibetans , but also shows the importance of such events in local adaptation of modern humans "