Proto-Shaman
09-08-2018, 10:31 PM
Pääbo extracted the mtDNA and then the whole genome from the finger bone. It was one of the best samples of ancient DNA ever discovered. Reich was asked to help with the analysis. It was found that the bone had a genome different from both Neanderthal and modern human DNA. It represented a previously unknown type of human, soon given the name ‘Denisovians’. (The name was chosen deliberately to avoid designating a new species, in recognition that the notion of distinct human species had been confounded by the interbreeding of Neanderthals and modern humans.) The Denisovians weren’t just genetically distinct; on the evidence of huge molar teeth also found in the cave, they would also have looked and behaved quite differently. By considering the number of mutations that differentiated Neanderthals, Denisovians and modern humans, and estimating the rate at which such mutations occurred, Reich and his colleagues concluded that the modern human lineage had split off between 770,000 and 550,000 years ago, and then the remaining lineage had split into Neanderthals and Denisovians between 470,000 and 380,000 years ago.
Then came another surprise: the Denisovians known from Siberia were found to be genetically closer to people from New Guinea than to anyone from mainland Eurasia. New Guinea! Nine thousand kilometres away and with a tropical climate. Reich weaves an explanation according to which the Denisovians separated into two lineages between 400,000 and 280,000 years ago, after which one branch – the Australo-Denisovians – interbred with the modern humans who were the direct ancestors of present-day New Guineans. The Australo-Denisovians are what Reich describes as a ‘ghost population’ – known only from genetics, since there are no identifiable skeletal remains. When in 2016 his laboratory assembled genome data from 51 ancient modern humans who lived in Europe between 47,000 and 7000 years ago, ‘a whole mob of ancient ghosts whirled out.’ These tell a story of successive populations arising, dispersing and mixing up their genomes. Some of them appear to be associated with Ice Age cultures defined by tool types, confirming Childe’s notion that such cultures equate to a ‘people’. The story culminates in a population dispersal from the south-east about 14,000 years ago that spread a relatively homogenous population across Europe and the Near East.
https://www.lrb.co.uk/v40/n17/steven-mithen/neanderthals-denisovians-and-modern-humans
Then came another surprise: the Denisovians known from Siberia were found to be genetically closer to people from New Guinea than to anyone from mainland Eurasia. New Guinea! Nine thousand kilometres away and with a tropical climate. Reich weaves an explanation according to which the Denisovians separated into two lineages between 400,000 and 280,000 years ago, after which one branch – the Australo-Denisovians – interbred with the modern humans who were the direct ancestors of present-day New Guineans. The Australo-Denisovians are what Reich describes as a ‘ghost population’ – known only from genetics, since there are no identifiable skeletal remains. When in 2016 his laboratory assembled genome data from 51 ancient modern humans who lived in Europe between 47,000 and 7000 years ago, ‘a whole mob of ancient ghosts whirled out.’ These tell a story of successive populations arising, dispersing and mixing up their genomes. Some of them appear to be associated with Ice Age cultures defined by tool types, confirming Childe’s notion that such cultures equate to a ‘people’. The story culminates in a population dispersal from the south-east about 14,000 years ago that spread a relatively homogenous population across Europe and the Near East.
https://www.lrb.co.uk/v40/n17/steven-mithen/neanderthals-denisovians-and-modern-humans