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Popular Archaeology Latest research shows that modern humans and archaic humans, or Denisovans, were mixing it up about 20,000 years ago on the mainland of East Asia. It is well-known today, based on various genetic studies, that some of the ancestors of modern humans interbred with Neanderthals, a closely-related human species or sub-species that lived 130,000 - 30,000 years ago in Eurasia. Less known is information that has recently emerged about the possibility that modern human ancestors were also busy with at least one other archaic human species. Additional information comes from a new study by researchers at Uppsala University. The study yielded findings that indicated people in East Asia share genetic material with archaic humans known as Denisovans, suggesting that the modern human ancestors of East Asians interbred with them about 20,000 years ago. News about the existence of Denisovans came to light when, in March 2010, it was announced that a finger bone fragment of a juvenile that lived about 41,000 years ago had been discovered in Denisova Cave (Altai Krai, Russia), an area that was also inhabited at the same time by modern humans and Neanderthals. The discovery of a tooth and toe bone from two other individuals of the same population added to the evidence. Based on analysis of mitochondrial DNA (mtDNA), researchers determined that the bone finds belonged to a new species of humans that lived contemporaneously with modern humans and Neanderthals. Says Mattias Jakobsson, who conducted the study along with Pontus Skoglund, "our study covers a larger part of the world than earlier studies, and it is clear that it is not as simple as we previously thought. Hybridization took place at several points in evolution, and the genetic traces of this can be found in several places in the world. We'll probably be uncovering more events like these." Previous studies indicated the occurrence of two separate hybridization points between archaic humans, who are genetically and morphologically different from modern humans, and modern human ancestors after leaving Africa. One occurred between Neanderthals and modern humans and the other between Denisovans and ancestors of Oceanians. But the latest study indicates that hybridization also occurred in East Asia. This was determined using genotype data, which greatly expands the database. Recent studies have been limited to using complete genomes of modern humans, only available from comparatively few individuals. Genotype data, on the other hand, is currently available from thousands of individuals. Using advanced computer simulation, the genotype data was compared with the genome sequence data derived from bones recovered archaeologically from Neanderthal locations and the recent Denisovan location. "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," says Jakobsson. "The findings show that gene flow from archaic human groups also occurred on the Asian mainland." But, adds co-researcher 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." The researchers hope that, with the use of more genomes from modern humans and continuing analysis and studies of fossil material, a more detailed and accurate picture may emerge about human prehistory. Details of the study can be found In this week's online edition of the Proceedings of the National Academy of Sciences.
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