Orangutan DNA boosts survival chances

Orangutans are far more genetically diverse than thought, a finding that could help their survival, say scientists delivering their first full DNA analysis of the critically-endangered ape.

The study, published yesterday in the science journal Nature, also reveals that the orangutan – the man of the forest – has hardly evolved over the last 15 million years, in sharp contrast to Homo sapiens and his closest cousin, the chimpanzee.

Once widely distributed across Southeast Asia, only two populations of the intelligent, tree-dwelling ape remain in the wild, both on islands in Indonesia.

Some 40,000 to 50,000 individuals live in Borneo, while in Sumatra deforestation and hunting has reduced a once robust community to about 7,000 individuals, according to the International Union for the Conservation of Nature.

These two groups split genetically about 400,000 years ago, considerably later than once thought, and today constitute separate albeit closely related species, Pongo abelii (Sumatra) and Pongo pygmaeus (Borneo), the study showed.

An international consortium of more than 30 scientists decoded the full genomic sequence of a female Sumatran orangutan, nicknamed Susie.

They then completed summary sequences of 10 more adults, five from each population.

“We found that the average orangutan is more diverse – genetically speaking – than the average human,” said lead author Devin Locke, an evolutionary geneticist at Washington University in Missouri.

Human and orangutan genomes overlap by about 97 per cent, compared to 99 per cent for humans and chimps, he said.

But the big surprise was that the far smaller Sumatran population showed more variation in its DNA than its close cousin in Borneo.

While perplexing, scientists said this could help boost the species’ chances of survival.

“Their genetic variation is good news because, in the long run, it enables them to maintain a healthy population” and will help shape conservation efforts, said co-author Jeffrey Rogers, a professor at Baylor College of Medicine.

Ultimately, however, the fate of this great ape – whose behaviour and languid expressions can be eerily human at times – will depend on our stewardship of the environment, he said.

“If the forest disappears, then the genetic variation won’t matter – habitat is absolutely essential,” he said. “If things continue as they have for the next 30 years, we won’t have orangutans in the wild.”