There are now eight recognized species of great apes, including humans, that are not extinct. Humans, three species of orangutans from Indonesia, two species of gorillas in Africa, and the chimpanzee/bonobo clade in Africa. Humans share the chimpanzee/bonobo clade vis-a-vis orangutans and gorillas, and are a sister clade to both chimpanzees and bonobos rather than being derived from one or the other of those species.
Six extant species of non-human great apes are currently recognized: Sumatran and Bornean orangutans, eastern and western gorillas, and chimpanzees and bonobos. However, large gaps remain in our knowledge of fine-scale variation in hominoid morphology, behavior, and genetics, and aspects of great ape taxonomy remain in flux. This is particularly true for orangutans (genus: Pongo), the only Asian great apes and phylogenetically our most distant relatives among extant hominids. Designation of Bornean and Sumatran orangutans, P. pygmaeus (Linnaeus 1760) and P. abelii (Lesson 1827), as distinct species occurred in 2001. Here, we show that an isolated population from Batang Toru, at the southernmost range limit of extant Sumatran orangutans south of Lake Toba, is distinct from other northern Sumatran and Bornean populations. By comparing cranio-mandibular and dental characters of an orangutan killed in a human-animal conflict to those of 33 adult male orangutans of a similar developmental stage, we found consistent differences between the Batang Toru individual and other extant Ponginae. Our analyses of 37 orangutan genomes provided a second line of evidence. Model-based approaches revealed that the deepest split in the evolutionary history of extant orangutans occurred ∼3.38 mya between the Batang Toru population and those to the north of Lake Toba, whereas both currently recognized species separated much later, about 674 kya. Our combined analyses support a new classification of orangutans into three extant species. The new species, Pongo tapanuliensis, encompasses the Batang Toru population, of which fewer than 800 individuals survive.
From Alexander Nater, et al., "Morphometric, Behavioral, and Genomic Evidence for a New Orangutan Species", Current Biology (2017).
Meanwhile, a 9.7 million year old great ape tooth has reportedly been found in Germany, outside the range of any previously known great ape population.
5 comments:
"Model-based approaches revealed that the deepest split in the evolutionary history of extant orangutans occurred ∼3.38 mya between the Batang Toru population and those to the north of Lake Toba, whereas both currently recognized species separated much later, about 674 kya."
And:
"we show that an isolated population from Batang Toru, at the southernmost range limit of extant Sumatran orangutans south of Lake Toba, is distinct from other northern Sumatran and Bornean populations".
Makes a massive destruction by the Toba eruption seem very unlikely!
Not at all obvious that they've been in that location continuously since then. Also, Toba destruction was disproportionately to the west and not the east of the explosion. Still, notable.
Difficult to make a convincing case they haven't been! The deepest split is between the new species and the other two at 3.38 my. That really places the two basal lines in close proximity at that time. Perhaps in China, and we won't know that unless we can get DNA from extinct Chinese orang-utans. But the split between Sumatran and Bornean lines is 674 kya, and it is very doubtful that split could have occurred anywhere other than close to those two islands. Especially when we consider that the population derived from the deepest split is still found in Sumatra.
@terryt The possibility that mainland populations went extinct, while only island populations that arrived in the LGM (perhaps repopulating territory vacated in Toba) is certainly plausible.
I very much doubt that scenario. If mainland populations went extinct then we would certainly expect any Sumatran population to be wiped out. Especially if we're going to consider the eruption might have wiped out a human population in India. But the fact that the split between the main Borneo and Sumatran population goes back nearly 700,000 years makes it unlikely that two independent mainland populations independently, and coincidentally, moved onto those separate islands a mere 70,000 years ago. Which islands, incidentally, would have been connected until some time after the Toba eruption. And we have another unlikely event in that the new population, which I agree could be the remnant of a much more widely spread mainland population, must have survived the eruption to be genetically different from the other two.
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