The Denisova cave is located in the Altai region. It has yielded highly fragmentary human remains associated with lithic industries from the Middle Paleolithic. The significance of these remains could only be understood after the ancient DNA contained within them had been sequenced. Morphologically, the most remarkable aspect of these remains is the considerable size of the dental crowns and the complex topography of the occlusal surfaces of the molars. Nuclear DNA analysis shows a kinship with Neanderthals, of which Denisovans are the Asian sister group. As with Neanderthals, genetic diversity is very low. The date of separation of the ancestral populations of the two lineages is estimated at around 400,000 years. The mitochondrial DNA of Denisovans is close to that of the common ancestor with Neanderthals. However, in Neanderthals, mitochondrial DNA seems to have undergone introgression towards the end of the Middle Pleistocene, from a group related to ancient Homo sapiens. In the Denisova cave, Denisovans, Neanderthals and modern humans succeeded one another, and an introgression of Neanderthal nuclear DNA into that of the Denisovans is attested.
Traces of Denisovian nuclear DNA are found in today's populations, mainly in Australia and Melanesia. At the time of the arrival of modern humans, this suggests a geographical extension of Denisovian populations over a large part of continental Asia, as far as the shores of the Indian Ocean. A number of Chinese fossils dated between 300 and 50,000 years ago, for which no ancient DNA has been analyzed, very probably belong to this sister group of European Neanderthals.
