An article published in the journal “Cell” describes a genetic research that focuses on the interbreeding between Homo Sapiens and Denisovans, a species of hominins known only thanks to a few bones that were preserved in conditions good enough to extract their DNA. A team of scientists at the University of Washington in Seattle compared the DNA of the Denisovans available with those of many modern humans from various different populations, concluding that there were at least two cases of interbreeding between the two species.
The advances in paleogenetics, the application of genetics to extinct species, allowed the reconstruction of the DNA of various hominins at least in part. This allowed to start studying the cases of interbreeding between modern humans and some other species similar enough to generate fertile hybrids, so much so that traces of “alien” DNA remained in humans living today as shown in the image (courtesy Browning et al./Cell. All rights reserved).
The case of interbreeding, technically called genetic admixture, best known is the one with Neanderthals, but genetic research already revealed traces of an interbreeding with the Denisovans. Those traces are present in particular in some populations of Oceania and in a lesser way in other Asian populations. This new research was conducted by comparing over 5,600 modern human genomes worldwide with that of the Denisovans developing a new method of analysis to compare whole genomes.
Today’s Papuans have about 5% of Denisovan DNA. The interesting thing is that the comparison of their genomes with those of other populations of Asia and Oceania revealed that some populations of East Asia show the genetic traces of a second admixture with the Denisovans independent from that occurred with the Papuans and the populations of the South Asia.
This conclusion came about by detecting different similarities between the DNA of the various populations and that of the Denisovans. Many genetic sequences of Papuans were very similar to those of Denisovans but in some populations of South Asia some genetic sequences were even more similar. Specifically, the populations in which those correspondences were found are the Chinese Han and Dai and the Japanese.
According to the reconstructions, the genetic admixture with the Denisovans took place quite early after the migration of modern humans out of Africa, about 50,000 years ago. The problem is to understand where those interbreedings occurred. For this reason, the researchers intend to carry out further genetic studies to better trace the interbreedings with the Denisovans and perhaps also with other hominins because in recent years there have been some surprises.