Present day humans in Southeast Asia have about one percent of DNA originating from Denisovans, an extinct species from the Homo genus. The researchers, from Uppsala University in Sweden, examined 1,500 worldwide human genome scans to search for genes unique to Denisovans; ones that weren't found in Neanderthals or chimpanzees.
Professor Mattias Jakobsson, co-author, told the Telegraph: 'The findings show that gene flow from archaic human groups also occurred on the Asian mainland'.
Interbreeding, also called hybridisation, has been found between ancestors of modern humans and Neanderthals. This is said to have occurred in Europe and Asia, after the great migration out of Africa, and between one and four percent of the DNA of non-Africans might have come from Neanderthals.
It was known that hybridisation occurred between Denisovans and humans in the tropical Pacific Ocean region, Oceania, but this study suggests there was also hybridisation on the Southeast Asia mainland.
Professor Jakobsson said: 'Previous studies have found two separate hybridisation events between so-called archaic humans – different from modern humans in both genetics and morphology – and the ancestors of modern humans after their emergence from Africa.
'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'.
Hybridisation is not uncommon in evolution, and can be found through genetic tracing, he explained, saying: 'We'll probably be uncovering more events like these'.
The study, published in the Proceedings of the National Academy of Sciences, found that mating occurred between our human ancestors and Denisovans approximately 20,000 years ago, or perhaps even earlier.
Graduate student Pontus Skoglund said: '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'.The Denisovans were discovered first in 2008, in the Denisova Cave in Siberia, which gave the species its current, temporary name. A bone fragment was found dating back 30,000 to 50,000 years. The Denisovans are part of the Homo genus, but do not yet have an official species name. Little is known of this species, as all the evidence comes from a finger bone and a molar tooth.