Washington: The Denisovans - newly discovered ancient human relative - crossed one of the world`s most prominent marine barriers in Indonesia, and interbred with modern humans moving through the area on the way to Australia and New Guinea, scientists have claimed.
Three years ago the genetic analysis of a little finger bone from Denisova cave in the Altai Mountains in northern Asia led to a complete genome sequence of a new line of the human family tree-the Denisovans.
Since then, genetic evidence pointing to their hybridisation with modern human populations has been detected, but only in Indigenous populations in Australia, New Guinea and surrounding areas.
In contrast, Denisovan DNA appears to be absent or at very low levels in current populations on mainland Asia, even though this is where the fossil was found.
Professor Alan Cooper of the University of Adelaide in Australia and Professor Chris Stringer of the Natural History Museum in the UK said that this pattern can be explained if the Denisovans had succeeded in crossing the famous Wallace`s Line, one of the world`s biggest biogeographic barriers which is formed by a powerful marine current along the east coast of Borneo. Wallace`s Line marks the division between European and Asian mammals to the west from marsupial-dominated Australasia to the east.
Professor Cooper, Director of the University of Adelaide`s Australian Centre for Ancient DNA, said that in mainland Asia, neither ancient human specimens, nor geographically isolated modern Indigenous populations have Denisovan DNA of any note, indicating that there has never been a genetic signal of Denisovan interbreeding in the area.
He said that the only place where such a genetic signal exists appears to be in areas east of Wallace`s Line and that is where we think interbreeding took place - even though it means that the Denisovans must have somehow made that marine crossing.
The study has been published in a Science opinion article.