Orangutans are an endangered species, with populations in some areas critically endangered. The new species, Pongo tapanuliensis, or the Tapanuli orangutan, was described as living only in an area of forest about 425 square miles in size. The team researching the Tapanuli orangutan contends that it’s the most endangered of all surviving great apes, with only about 800 left.
In 2013, researchers involved in conservation efforts in an area of North Sumatra province known as the Batang Toru ecosystem recovered parts of a skeleton from an adult male orangutan killed by local residents. They were surprised to find singular characteristics that consistently differed from other Sumatran orangutans, including in the measurements and overall shape of its skull, jaw and teeth, said Matthew G. Nowak, a conservation biologist with the Sumatran Orangutan Conservation Program, an organization involved in the research.
“When we realized that Batang Toru orangutans are morphologically different from all other orangutans, the pieces of the puzzle fell into place,” said Dr. Michael Krützen, a professor at the University of Zurich and a member of the research team.
Researchers then conducted what they called the “largest genomic study of wild orangutans to date,” comparing the genes from the recovered orangutan with data collected in the past from other field sites on Sumatra. They found that the Tapanuli population had become isolated from other Sumatran orangutan populations sometime in the last 10,000 to 20,000 years.
They also found that the Tapanuli’s orangutan’s lineage was ancient — between three and three and one-half million years old — and that they appeared to be direct descendants of the orangutan ancestors that crossed into what is now Indonesia and Malaysia from mainland Asia.
“We have learned how little we actually knew about orangutan evolution despite many decades of research and how much more there is to learn,” Dr. Meijaard said. “Orangutans are ancient creatures, as old as the very first members of our own genus Homo.”
The researchers acknowledged that there are limitations in their study, as they had access to only a single skeleton and two individual genomes. But they noted that other species have been defined with a single specimen.
Dr. Biruté Mary Galdikas, a Canadian primatologist who has studied orangutans for 46 years and led conservation efforts on the neighboring island of Borneo, said she was pleased – but not necessarily surprised – by the announcement.
“It was the talk 50 years ago, that there were two types, including one that had long fingers,” she said of descriptions made by residents of that area of Sumatra. .
“So what they have done is solidified the evidence, using anatomical evidence and genetic evidence, and evidence from the population.”
Dr. Galdikas, president of Orangutan Foundation International, said she hoped media attention over the announcement will further efforts to protect remaining orangutan populations in Borneo and Sumatra.
She also said she hoped it would spark new scientific debate on whether the three subspecies of the Bornean orangutan should themselves be elevated to full species of great ape, in particular the orangutan of eastern Borneo.