A Second Clue: Genome Sequencing
To figure out what was going on, Krützen, Nater and the team knew they needed to know the genetics of not just the maternal line but of the paternal as well. For that, they couldn’t use mitochondrial DNA but instead needed autosomal DNA, which is inherited from both parents and found in the cell’s nucleus. And to get that, old strands of hair wouldn’t do.
Instead, from 2011 to 2016, they sequenced and analyzed the genomes of 37 wild orangutans using blood samples collected at rehabilitation centers across Borneo and Sumatra.
Once again, the scientists were surprised by the results. The DNA showed three distinct genetic lineages: one of Bornean orangutans, another of Sumatran, and a third, which was the oldest: the Batang Toru animals.
This was the moment, Krützen said, “we knew this [Batang Toru] population was special.”
Yet while the geneticists suspected the Tapanuli orangutans could be a new species, they wanted to see if other significant distinctions existed as well.
Anatomical Differences
Enter Indonesian scientist Anton Nurcahyo. He began studying anatomical variations between geographically separate orangutan populations using morphometrics — the quantitative analysis of the size and shape of skulls and bones — for his doctorate at Australian National University.
To detect differences, Nurcahyo needed to analyze orangutan skeletons, and a lot of them. From 2014 to 2015, he traveled to dozens of museums, rescue centers and other institutions across Southeast Asia, Europe and the United States to examine specimens. At each, he spent weeks taking detailed measurements of hundreds of points on a variety of bones. For the skull alone, he made more than 200 separate measurements, including the width, length and position of the eye sockets, the line and height of the mandible, and the size of the brain case.
Information on the origin of the specimens was often vague or incomplete. For instance, Nurcahyo recalls how a Swiss museum listed several of its skulls as coming from the Kapuas River in Borneo. But because there are two such rivers — one in West Kalimantan province and another in Central Kalimantan, called Kapuas Kahayan — Nurcahyo didn’t know which one it referred to. As a result, he had to contact the missionary group that had originally donated the skulls to find out. Indeed, he often had to dig into the diaries of explorers to determine exactly where a specimen had been collected.
Ultimately, Nurcahyo gathered data from about 500 orangutan skeletons. But none were known to be from Batang Toru.
Meanwhile, other researchers were also searching for orangutan skeletons confirmed to be from Batang Toru. Meijaard searched more natural history museums, while another of Rijksen’s former students, Gabriella Fredriksson, now the SOCP’s Tapanuli program coordinator, probed communities living in the Batang Toru area. Yet she had to take care. To make sure nobody mistook her interest as a request to kill an orangutan, Fredriksson and her team hid their objective and only asked indirect questions, like what animals were hunted and what parts were kept. In some villages in Indonesia, hunters kept skulls as trophies. But not these. The local Batak people tended to consume every part of what they hunted.
There was still no orangutan skull from Batang Toru.
But that soon changed.
This story first appeared on Mongabay
South Africa Today – Environment
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