04.11.2020

Denisovan Introgression, High Altitude Adaptation, and Tibetan Population History

Colloquium by Dr. Xinjun Zhang

Title: Denisovan Introgression, High Altitude Adaptation, and Tibetan Population History

Speaker: Dr. Xinjun Zhang (Davis University of California)

Date: Wednesday, 4 November 17:00

Venue: Zoom, Link will be published on the day before the talk

Abstract:

The discovery of Denisovans is one of the most exciting findings in human evolution in the past decade. The striking similarity between sequences of the EPAS1 gene in Denisovans and modern Tibetans suggested adaptive introgression that facilitated high altitude adaptation. However, the time and geographic ranges where the admixture between species was made remain unknown. In this talk, I will show that ancestral Tibetans experienced two pulses of Denisovan introgression, among which a group more alike the individual from the Denisova cave introduced the adaptive EPAS1 haplotype around 43,000 years ago. The positive selection on EPAS1, on the other hand, started after the Last Glacial Maximum at around 12,000 years ago. This suggests that the Denisovan EPAS1 variants were not immediately beneficial in Tibetans, likely because introgression occurred at low altitudes. I further leveraged the up-to-date genetic and archaeological evidence and proposed two comprehensive testable models for the peopling of Tibetan Plateau.