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Denisovan or Denisova hominin ( ) is an extinct species of human in the genus ''Homo''. The species is sometimes given the name ''Homo sp. Altai'',〔(【引用サイトリンク】title=Exploring Taxonomy )〕 and ''Homo sapiens ssp. Denisova''.〔(【引用サイトリンク】title=Taxonomy - Homo sapiens ssp. Denisova (Denisova hominin) )〕 In , scientists announced the discovery of a finger bone fragment of a juvenile female who lived about 41,000 years ago, found in the remote Denisova Cave in the Altai Mountains in Siberia, a cave which has also been inhabited by Neanderthals and modern humans. Two teeth belonging to different members of the same population have since been reported. More recently, in November 2015, a tooth fossil containing DNA was reported to have been found and studied. Analysis of the mitochondrial DNA (mtDNA) of the finger bone showed it to be genetically distinct from the mtDNAs of Neanderthals and modern humans.〔 Subsequent study of the nuclear genome from this specimen suggests that this group shares a common origin with Neanderthals, that they ranged from Siberia to South-East Asia, and that they lived among and interbred with the ancestors of some modern humans, with about 3% to 5% of the DNA of Melanesians and Aboriginal Australians deriving from Denisovans.〔name="Callaway.〕〔"〕〔"About 3% to 5% of the DNA of people from Melanesia (islands in the south-west Pacific Ocean), Australia and New Guinea as well as aboriginal people from the Philippines comes from the Denisovans." (Oldest human DNA found in Spain ) --Elizabeth Landau's interview of Svante Paabo, accessdate=2013-12-10〕 DNA discovered in Spain suggests that Denisovans at some point resided in Western Europe, where Neanderthals were previously thought to be the only inhabitants. A comparison with the genome of a Neanderthal from the same cave revealed significant local interbreeding with local Neanderthal DNA representing 17% of the Denisovan genome, while evidence was also detected of interbreeding with an as yet unidentified ancient human lineage. Similar analysis of a toe bone discovered in 2011 is underway, while analysis of DNA from two teeth found in layers different from the finger bone revealed an unexpected degree of mtDNA divergence among Denisovans.〔 In 2013, mitochondrial DNA from a 400,000-year-old hominin femur bone from Spain, which had been seen as either Neanderthal or ''Homo heidelbergensis'', was found to be closer to Denisovan mtDNA than to Neanderthal mtDNA. ==Discovery== The Denisova Cave is located in south-western Siberia, in the Altai Mountains near the border with China and Mongolia. It is named after Denis, a Russian hermit who lived there in the 18th century. The cave was originally explored in the 1970s by Russian paleontologist Nikolai Ovodov, who was looking for remains of cave bears. In 2008, Michael Shunkov from the Russian Academy of Sciences and other Russian archaeologists from the Institute of Archaeology and Ethnology of Novosibirsk investigated the cave. They found the finger bone of a juvenile hominin, dubbed the "X woman" (referring to the maternal descent of mitochondrial DNA〔) or the Denisova hominin. Artifacts, including a bracelet, excavated in the cave at the same level were dated using radiocarbon and oxygen isotopes to around 40,000 BP.〔http://siberiantimes.com/science/casestudy/features/f0100-stone-bracelet-is-oldest-ever-found-in-the-world/〕 Excavations have since revealed human artifacts showing an intermittent presence going back 125,000 years.〔Marshall, Michael (April 2014), "Mystery Relations" in ''New Scientist'' (5, April 2014)〕 A team of scientists led by Johannes Krause and Svante Pääbo from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, sequenced mtDNA extracted from the fragment. The cool climate of the Denisova Cave preserved the DNA.〔 The average annual temperature of the cave remains at 0 °C, which has contributed to the preservation of archaic DNA among the remains discovered. The analysis indicated that modern humans, Neanderthals, and the Denisova hominin last shared a common ancestor around years ago. The mtDNA analysis further suggested that this new hominin species was the result of an earlier migration out of Africa, distinct from the later out-of-Africa migrations associated with modern humans, but also distinct from the earlier African exodus of ''Homo erectus''.〔 Pääbo noted that the existence of this distant branch creates a much more complex picture of humankind during the Late Pleistocene. This work shows that the Denisovans were actually a sister group to the Neanderthals,〔''Nature'' Vol 468, p.1053〕 branching off from the human lineage 600,000 years ago, and diverging from Neanderthals, probably in the Middle East, 200,000 years later.〔Marchall, Michael (April), op cit p.36〕 Later in 2010, a second paper from the Svante Pääbo group reported the prior discovery, in 2000, of a third upper molar from a young adult, dating from about the same time (the finger was from level 11 in the cave sequence, the tooth from level 11.1). The tooth differed in several aspects from those of Neanderthals, while having archaic characteristics similar to the teeth of ''Homo erectus''. They performed mitochondrial DNA analysis on the tooth and found it to have a sequence different from but similar to that of the finger bone, indicating a divergence time about 7,500 years before, and suggesting that it belonged to a different individual from the same population. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Denisovan」の詳細全文を読む スポンサード リンク
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