Key to Tibetans' altitude adaptation may lie in extinct denisovans

A new study has found that the altitude adaptation in Tibet might have been caused by the introgression of DNA from extinct Denisovans or Denisovan-related individuals into humans.

According to the scientists, this work sheds new light into understanding human's adaptation to diverse environments including temperature extremes, new pathogens, and high altitude.

The evolutionary adaptation has allowed Tibetans to have no trouble living at 13,000 feet all the year round. 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 have 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.

As per the previously reported findings, scientists found the evidence for Denisovan admixture throughout Southeast Asia. Given to this conclusion and their findings, researchers have 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.

This study presented by researchers from BGI and University of California, was published online in Nature.