The percentage of Denisovan DNA is the highest among the indigenous tribal communities in India, finds the GenomeAsia 100K Pilot study. A significantly high amount of DNA of these archaic humans is also found in non-Indo-European-speaking populations of the sub-continent.
The Denisovan ancestry, however, is considerably less among Asians of clear Indo-European descent, show data from the study of 1,739 Asian individuals from 219 populations, which has recently been published in Nature.
This lends further credence to the theory that the Indo-European-speaking migrants have entered the Indian subcontinent from the northwest.
The Denisovans were added much more recently to the human family tree after the discovery of the fossilised remains of this extinct species of humans in the Siberian mountains.
However, the Denisovan ancestry present among the indigenous populations of the Indian sub-continent was that of the Sundae Denisovans, and not that of Siberia. The ancestry remains strongest in the Sunda landmass of Southeast Asia.
So, the study concludes that admixture between Sunda Denisovans and the earliest anatomical modern humans to reach the region most likely occurred somewhere in the vicinity of the former Sunda that comprises the Malay Peninsula and the Malay Archipelago islands.
The Denisovan DNA in the South Asian populations was consistent with that found also among the Melanesians of Papua New Guinea and the Aeta, a Negrito tribal society from Luzon Island in the Philippines, even though, with them, the level of Denisovan ancestry was considerably higher.
While high levels of Denisovan ancestry was found in Philippine Negrito groups, it was not the same in Malay or Andaman Negritos.
The study also found that the average level of Denisovan ancestry was significantly different between tribal (Adivasi), lower-caste, high caste and Pakistan groups. This is consistent with the scenario that the Indo-European migrants admixed with an indigenous South Asian (ancestral South Indian) group who had high levels of Denisovan ancestry.
These findings are significant because they help understand the admixture between Denisovans and modern humans, as well as the details where and when exactly this might have taken place.
It underscores the fact that there are different ancestral groups or lineages in Asia in sharp contrast with people of European descent, and they could not all be grouped into just one ancestral lineage.
The mitochondrial DNA (mtDNA) of Denisovans was found to be genetically distinct from Neanderthals. The mtDNA from the remains discovered in Denisova Cave differs from that of modern humans by 385 nucleotides out of approximately 16,500. Modern humans differ from Neanderthals by around 202 bases.