UGI External Seminar - Dr Maximilian Larena - Uppsala Universitat

Abstract : Multiple lines of evidence show that modern humans interbred with archaic Denisovans. Although the intertwined demographic history between Denisovans and Australasians is being uncovered, our knowledge of their specific interactions in Island Southeast Asia (ISEA) remains limited. This is especially important given that some present-day populations of the Philippines, who self-identify as “Negritos” and who are genetically related to Australopapuans, display significant levels of Denisovan ancestry.To deepen our understanding of past Denisovan-Australasian interactions in the ISEA region, we comprehensively investigated the archaic ancestry of > 1,000 individuals from 118 distinct ethnic groups of the Philippines, including 25 ethnolinguistically diverse Negrito populations. We show that Ayta Magbukon possess the highest level of Denisovan ancestry in the world-∼30%-40% greater than that of Australians and Papuans-consistent with an independent admixture event into Negritos from Denisovans. Together with the recently described Homo luzonensis, we suggest that there were multiple archaic species that inhabited the Philippines prior to the arrival of modern humans and that these archaic groups may have been genetically related. Altogether, our findings unveil a likely complex presence of diverse Islander Denisovan populations, who differentially admixed with incoming Australasians across multiple locations and at various points in time. Consequently, this led to variable levels of Denisovan ancestry in the genomes of Philippine Negritos and Papuans. In ISEA, Philippine Negritos later admixed with East Asian migrants who possess little Denisovan ancestry, which subsequently diluted their archaic ancestry. Some groups though, such as the Ayta Magbukon, minimally admixed with the more recent incoming migrants. For this reason, the Ayta Magbukon retained most of their inherited archaic tracts and left them with the highest level of Denisovan ancestry in the world.