The Tapanuli orangutan ( Pongo tapanuliensis) lives in the Batang Toru area in North Sumatra, Indonesia, south of and isolated from Sumatran orangutans (Pongo abelii.) It is genetically, physically, and even behaviorally different than the other two species of orangutans.
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.
Following the discovery of the skeletal material, believed to have come from a Tapanuli orangutan killed in a human-animal conflict in 2013, an global team of researchers set out to understand more about the distant ape relative of humans. Sumatran and Bornean orangutans separated around 674,000 years ago, the team estimates. The results confirmed their observations, with another surprising revelation: not only did they uncover three very old evolutionary lineages, but the newly discovered population was the oldest.
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".
"Great apes are among the best-studied species in the world", said Erik Meijaard of the Australian National University in a press release.
By the latest estimate, there should be no more than 800 individuals belonging to the new orangutan species. If after 200 years of serious biological research we can still find new species in this group, what does it tell us about all the other stuff that we are overlooking: hidden species, unknown ecological relationships, critical thresholds we shouldn't cross?
He added: "It has a smaller skull, but larger canine teeth than other orangutan species".
"If steps are not taken quickly to reduce current and future threats to conserve every last remaining bit of forest we may see the discovery and extinction of a great ape species within our lifetime", they said.
Wiratno, director-general of natural resources conservation and ecosystem at Indonesia's Ministry of Environment and Forests, who like many Indonesians only uses his first name, said Batang Toru is not included in the protected forest area.
"It is very exciting to discover a new great ape species in the 21st century".