A international team of researchers studying DNA patterns from modern and archaic humans has uncovered new clues about the movement and intermixing of populations in Asia more than 40,000 years ago.
     Scientists from Harvard Medical School and the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, found that Denisovans - a recently identified group of archaic humans whose DNA was extracted last year from a finger bone excavated in Siberia - contributed DNA not just to present-day New Guineans, but also to aboriginal Australian and Philippine populations.
     According to David Reich, professor of genetics at Harvard Medical School, "Denisova DNA... is so recognisable that you can detect even a little bit of it in one individual. This shows the power of sequencing ancient DNA as a tool for understanding human history."
     The patterns the researchers found can only be explained by at least two waves of human migration: the first giving rise to the aboriginal populations that currently live in Southeast Asia and Oceania, and later migrations giving rise to relatives of East Asians who now are the primary population of Southeast Asia.
     According to Mark Stoneking, professor at the Max Planck Institute and senior author of the paper, Denisovans must have inhabited an extraordinarily large ecological and geographic range, from Siberia to tropical Southeast Asia. "The fact that Denisovan DNA is present in some aboriginal populations of Southeast Asia but not in others... can most easily be explained if Denisovans lived in Southeast Asia itself."
     Denisovans were a distinct group of archaic humans that lived more than 30,000 years ago and contributed genes to present-day New Guineans. Denisovans were neither Neandertals nor early modern humans, though they shared a common ancestry.
     The paper helps fill in some pieces in the evolutionary puzzle that began after early humans left Africa, and reinforces the view that humans have intermixed throughout history.
     The researchers conclude that Denisovans interbred with modern humans in Southeast Asia at least 44,000 years ago before the time of the separation of the Australians and New Guineans, and that Southeast Asia was first colonised by modern humans unrelated to present-day Chinese and Indonesians - that these and other East Asians arrived in later migrations.

Edited from EurekAlert! (22 September 2011)