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onomy and phylogeny See also: Orangutan–human last common ancestor The orangutan was first described scientifically in 1758 in the Systema Naturae of Carl Linnaeus as Homo Sylvestris.:20 It was renamed Simia pygmaeus in 1760 by his student Christian Emmanuel Hopp and given the name Pongo by Lacépède in 1799.:24–25 The populations on the two islands were suggested to be separate species when P. abelii was described by French naturalist René Lesson in 1827. In 2001, P. abelii was confirmed as a full species based on molecular evidence published in 1996,:53 and three distinct populations on Borneo were elevated to subspecies (P. p. pygmaeus, P. p. morio and P. p. wurmbii). The description in 2017 of a third species, P. tapanuliensis, from Sumatra south of Lake Toba, came with a surprising twist: it is more closely related to the Bornean species, P. pygmaeus than to its fellow Sumatran species, P. abelii. Head
shots of male Bornean, Sumatran and Tapanuli orangutans Flanged male Bornean, Sumatran and Tapanuli orangutans The Sumatran orangutan genome was sequenced in January 2011. Following humans and chimpanzees, the Sumatran orangutan became the third species of great ape to have its genome sequenced. Subsequently, the Bornean species had its genome sequenced. Genetic diversity was found to be lower in Bornean orangutans (P. pygmaeus) than in Sumatran ones (P. abelii), despite the fact that Borneo is home to six or seven times as many orangutans as Sumatra. The researchers hope these data may help conservationists save the endangered ape, and also prove useful in further understanding of human genetic diseases. Similarly to gorillas and chimpanzees, orangutans have 48 diploid chromosomes, in contrast to humans, which have 46.:9 According to molecular evidence, within apes (superfamily Hominoidea), the gibbons diverged during the early Miocene between 24.1 and 19.7 million years ago (mya)
, and the orangutans split from the African great ape lineage between 19.3 and 15.7 mya. Israfil and colleagues (2011) estimated based on mitochondrial, Y-linked, and X-linked loci that the Sumatran and Bornean species diverged 4.9 to 2.9 mya.(Fig. 4) By contrast, the 2011 genome study suggested that these two species diverged around 400,000 years ago, more recently than was previously thought. Also, the orangutan genome was found to have evolved much more slowly than chimpanzee and human DNA. A 2017 genome study found that the Bornean and Tapanuli orangutans diverged from Sumatran orangutans about 3.4 mya, and from each other around 2.4 mya. Orangutans travelled from Sumatra to Borneo as the islands were connected by land bridges as parts of Sundaland during recent glacial periods when sea levels were much lower. The present range of Tapanuli orangutans is thought to be close to where ancestral orangutans first entered what is now Indonesia from mainl