A mystery in the evolution of humans ignited the interest of scientists when the extinct human genome of Denisovans was found to have interbred with another unknown species.
David Reich, lead author of the study who is also a geneticist and professor in the department of genetics at the Harvard Medical School, had closely examined this extinct human genome and found certain irregularities.
Denisovans are an extinct genome of the hominin species, whose DNA has an entirely different set from its native group. Scientists believe that this is either from an entirely different species altogether or one that is already known from their fossils but not yet closely analyzed because of lack of genetic samples.
The mystery group showed some traces in the Denisovan genome, which is a known extinct human genome found from two pieces of teeth and a piece of finger bone lying in a cave in Siberia. The researchers were able to do sequencing of genomes accurately that allowed them to recreate for the first time the physical appearance of the Denisovans.
Reich's observations supported the general belief that the genome was a close relative of the Neanderthals. The ancestry of the Denisovans had come from our predecessors 400,000 years ago and branched out to separate them from the Neanderthal species.
It could be supposed that both the Denisovans and Neanderthals would have the same extent of distinct features from modern humans. However, according to Reich, the "Denisovans appear more distinct from modern humans than Neanderthals."
The most probable cause for this remarkable discovery is an interbreeding between the Denisovans and another unknown species.
"Denisovans harbour ancestry from an unknown archaic population, unrelated to Neanderthals," said Reich.
But the real mystery lies in which species the Denisovans had interbred with. Some theorize that it could be the H. heidelbergensis or the Homo Erectus. To find answers to this mystery, scientists will need to extract DNA from the mentioned species, which could be very tough since some species thrived in warm environments where DNA could easily disintegrate.
The study was presented on Monday during a DNA discussion at the The Royal Society in London.
