London: Scientists have claimed that human evolution also occurred outside Africa, after they found evidence that people in East Asia share genetic material with Denisovans, known as the mysterious cousins of Neanderthals.
A team at Uppsala University in Sweden says that hybridisation took place at several points in evolution and the genetic traces of this can be found in several places in the world, `The Daily Telegraph` reported.
"We`ll probably be uncovering more events like these. Previous studies have found two separate hybridisation events between so-called archaic humans -- different from modern humans in both genetics and morphology -- and ancestors of modern humans after their emergence from Africa.
"There was hybridisation between Neanderthals and the ancestors of modern humans outside of Africa and hybridization between Denisovans (who got the name from the cave in Siberia where they were first found) and the ancestors of indigenous Oceanians.
"The genetic difference between Neanderthals and Denisovans is roughly as great as the maximal level of variation among us modern humans," Prof Mattias Jakobsson, who led the team, was quoted as saying.
For their research, the scientists use genetic data from more than 1,500 modern humans from all over the world.
Prof Jakobsson said: "We found that individuals from mainly Southeast Asia have a higher proportion of Denisova- related genetic variants than people from other parts of the world, such as Europe, America, West and Central Asia, and Africa. The findings show that gene flow from archaic human groups also occurred on the Asian mainland."
Added team member Pontus Skoglund: "While we can see that genetic material of archaic humans lives on to a greater extent than what was previously thought, we still know very little about the history of these groups and when their contacts with modern humans occurred."
Because they find Denisova-related gene variants in south east Asia and Oceania, but not in Europe and America, the scientists suggest that hybridisation with Denisova man took place about 20 million years ago, but could also have occurred earlier.
This is long after the branch that became modern humans split off from the branch that led to Neanderthals and Denisovans some 300,000 to 500,000 years ago.
Prof Jakobsson said: "With more complete genomes from modern humans and more analyses of fossil material, it will be possible to describe our prehistory with considerably greater accuracy and richer detail."
The findings have been published in the `PNAS` journal.