New orangutan species discovered in Sumatra

Orangutans in general are at risk of extinction. Image Credit: CC BY-SA 2.5 Kabir Bakie

Scientists studying apes in northern Sumatra have identified a small population of an entirely new species. Scientists studying apes in northern Sumatra have identified a small population of an entirely new species.The discovery, which has been described as ‘exciting’ by researchers, is particularly important because there were only thought to be two distinct types of orangutan – Bornean and Sumatran.

This third species has been named the Tapanuli orangutan, or Pongo tapanuliensis.
Sadly however, there are thought to be fewer than 800 individuals left, making this the most endangered of all the great apes and the most at risk of going extinct in the near future.
“It is worrying that this species is under so much threat – we have hunting in the area, there is a gold mine [and] there is a hydroelectric plant planned in an area where we find a very high density of the new species,” said study co-author Serge Wich from Liverpool John Moores University.

The researchers also carried out an analysis of the entire genomes of 37 orangutans from across Borneo and Sumatra, allowing them to unpick the animals’ evolutionary “family tree”.

The results suggest that orangutans north of Lake Toba branched off about 3.4m years ago from the more southerly population of ancestral orangutans that first arrived from mainland Asia, giving rise to the Sumatran species. A further split from the population south of Lake Toba occurred about 674,000 years ago, giving rise to the Bornean orangutans as well as the newly discovered species that, like its ancestors, live south of Lake Toba.

“The new species represents the most ancestral line of living orangutans,” said Wich.

The revelations, the team add, have also solved a mystery.

Previous research had found that a type of DNA which is passed down only by mothers, known as mitochondrial DNA, is more similar between Bornean and Tapanuli orangutans, but nuclear DNA – which includes genes from both parents – is more similar between Sumatran and Tapanuli orangutans.
The new study reveals that even after the split between orangutans north and south of Lake Toba, the animals continued to interbreed – likely a result of roving males – resulting in mixing of the nuclear DNA. This was curtailed about 100,000 years ago – a date close to the supervolcanic eruption at Lake Toba – and stopped altogether between 20,000 and 10,000 years ago. Crucially, since the females stayed put, so too did the mitochondrial DNA.

William Amos, professor of evolutionary genetics at the University of Cambridge who was not involved in the study, said it was difficult to be exact when it came to the timings of splits in the evolutionary family tree, but that the evidence for a new species stacked up. “I’m entirely happy that this is at a level where we would recognise [the Tapanuli orangutans] as a different species or at least a subspecies,” he said. “This is clearly a really different population.”

Dr Andrew Marshallof University of York, said that the study highlighted the importance of conservation, and added that there might even be further species of great ape to be discovered.

But Professor Volker Sommer from University College London was less bowled over, pointing out that there is no clear criteria for what constitutes a new species. “Any bunch of expertised biologists can invent a new species, if they get their arguments together,” he said.