April 11 (UPI) -- The Denisovan family tree was more diverse than previously realized. Through the analysis of ancient and modern DNA, scientists discovered a previously unidentified Denisovan lineage.
"We compared the genomes of modern -- living -- people in Indonesia and New Guinea and found pieces that match the Denisovan genome," Murray Cox, professor of computational biology at Massey University in New Zealand, told UPI. "However, they didn't match perfectly, which is what we would expect if the Denisovans from the cave and the Denisovans that mixed into Papuans came from the same group."
Instead, Cox and his research partners found the genetic signatures of two Denisovan-related groups, both different than the original cave dwelling Denisovans.
"One of these groups is as different from Denisovans from the cave as from Neanderthals, and so should probably be given its own name," Cox said.
That new species, found on the island of Luzon, is much older than the groups of Denisovans described in Cell, but both discoveries highlight the importance of Southeast Asia in the story of human evolution.
Until now, most scientists assumed the hominin diversification played out across Europe and Eurasia, but the latest findings suggest researchers were misled by ancient DNA. Because ancient DNA breaks down in hot climates and is more likely to be preserved in cold climates, more ancient DNA has been recovered in Europe and Eurasia.
"The oldest DNA from the tropics is only about 6,000 years old, which isn't helpful for questions about archaic hominins," Cox said. "It's unlikely that we will ever go back much further than that."
However, by comparing what DNA scientists can salvage from tropical hominin remains with modern human genomes, researchers can gain new insights into the complexity of human evolution in Southeast Asia.
"If you look at modern human diversity, and biological diversity in general -- plants and animals, for example -- most diversity is in the tropics," Cox said. "This study -- and the Luzon hominin -- fits into a much bigger body of scientific findings that show that this was also true for archaic hominins; their center of gravity was in the tropics too."
According to Cox, the latest findings wouldn't have been possible without the work of scientists at the Eijkman Institute for Molecular Biology in Indonesia, especially Herawati Sudoyo, co-director of the institute. Just as ancient DNA is biased toward Western sources, so too is the work of deciphering the story of human evolution.
"There has been a lot of criticism lately of western scientists taking from developing countries and not giving back," Cox said. "We purposely work very differently. I've had a genuine partnership with the Eijkman for nearly 20 years, and Indonesian researchers played key lead roles in this project."