Genetic analysis has found clear traces that humans and Denisovans interbred in the past. The Philippine ethnic group known as the Ayta Magbukon has the highest level of Denisovan ancestry in the world.
The Negritos group in the Philippines comprises some 25 different ethnic groups, scattered throughout the Andaman archipelago in South-East Asia. They were once considered to be a single population, but the more researchers looked into it, the more they found that Negritos are actually very diverse.
In the new study, Maximilian Larena of Uppsala University and colleagues set out to establish the demographic history of the Philippines. Their project involved indigenous cultural communities, local universities, as well as official and non-governmental organizations from the area. With everyone working together, they were able to analyze 2.3 million genotypes from 118 ethnic groups in the Philippines — including the diverse Negrito populations.
The results were particularly intriguing for a population called the Ayta Magbukon, which still occupy vast swaths of their ancestral land and continue to coexist with the lowland population surrounding them. The Ayta Magbukon seem to possess the highest level of Denisovan ancestry in the world.
“We made this observation despite the fact that Philippine Negritos were recently admixed with East Asian-related groups—who carry little Denisovan ancestry, and which consequently diluted their levels of Denisovan ancestry,” said Larena “If we account for and masked away the East Asian-related ancestry in Philippine Negritos, their Denisovan ancestry can be up to 46 percent greater than that of Australians and Papuans.”
This finding, along with the recent discovery of a small-bodied hominin called Homo luzonensis, suggests that multiple hominin species inhabited the Philippines prior to the arrival of modern humans — and these groups likely interbred multiple times.
The Denisovans are a mysterious group of hominins identified in 2010 based on mitochondrial DNA (mtDNA) extracted from a juvenile female finger bone from the Siberian Denisova Cave. Although researchers haven’t found numerous traces of DNA, they’ve discovered traces of their DNA in modern populations. Apparently, this group in the Philippines has the highest percentage of Denisovan DNA in the world — at least that we’ve found so far.
“This admixture led to variable levels of Denisovan ancestry in the genomes of Philippine Negritos and Papuans,” co-author Mattias Jakobsson said. “In Island Southeast Asia, 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 were left with the highest level of Denisovan ancestry in the world.”
Researchers hope to sequence more genomes and better understand “how the inherited archaic tracts influenced our biology and how it contributed to our adaptation as a species,” Larena concludes.
Journal Reference: “Philippine Ayta possess the highest level of Denisovan ancestry in the world”