It was only after identifying key differences in the teeth, skull, DNA, diet and calls of the Tapanuli orangutan (Pongo tapanuliensis) that the global team concluded they had found a unique species.
Unfortunately, the population of these newfound orangutans is so small, they've immediately joined the list of some of the most endangered primates in the world.
Previous study results combined with the new genome sequencing of 37 orangutans showed a picture that was consistent with the morphological findings.
Outwardly, the Tapanuli orang utan bears a closer resemblance to its Bornean counterpart, with cinnamon-coloured fur that is frizzier than its Sumatran relative.
The discovery brings the count of orangutan species to three, as the Tapanuli orangutan joins the ranks of Sumatran and Bornean orangutans, which were only distinguished from each other in 1996.
With only a population of 800, the Tapanuli orangutans, which have thick curly hair, became the third species of the giant ape found in the country.
In 1997, a team of Australian researchers discovered an isolated population of orangutans in the Tapanuli districts of North Sumatra, and it was assumed the animals belonged to one of the two known species: Pongo abelii, endemic to Sumatra, and Pongo pygmeaeus of the neighboring island of Borneo.More news: Thornton Police have Walmart shooting suspect in custody
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"We identified three very old evolutionary lineages among all orangutans, despite only having two species now described", Maja Mattle-Greminger, a postdoctoral researcher at UZH, said in the statement. The Bornean and Sumatran species, in contrast, split from each other only around 674,000 years ago.
Dr Maja Mattle-Greminger, of University of Zurich, who led the genomic analysis along with Dr Alexander Nater, said: "For quite some time, we had been working on genomic data to investigate the genetic structure and evolutionary history of all existing orangutan populations". The team of researchers believes that it is the most endangered of all surviving great apes, with only about 800 left. "Humans are conducting a vast global experiment, but we have near-zero understanding of what impacts this really has, and how it could ultimately undermine our own survival".
All three species of orangutan face dire threats to their populations at the hands of humans.
Puji Rianti, a researcher from Bogor Agricultural University, told Anadolu Agency that these physical differences were one of the reasons these orangutans were declared a separate species.
In addition, the new species is also threatened with extinction due to widespread hunting in Batang Toru.
Early research indicated both behavioural and genetic differences, but it wasn't enough to warrant the designation of a new species - since the world only has six great ape species overall, that would be a pretty big deal.
"It isn't an everyday event that we find a new species of great ape, so indeed the discovery is very exciting", says senior researcher, evolutionary anthropologist Michael Krutzen from the University of Zurich in Switzerland.