for National Geographic News
Human activity is directly responsible for the rapid, large-scale decline of orangutan populations in parts of Asia, according to a new gene study.
The findings represent the first time scientists have used genetic evidence to link human actions to fewer numbers of the endangered ape.
The study also suggests that the decline may be steeper than previously thought and that the apes could soon be extinct.
"It is clear that the remaining population of orangutans [in the Malaysian region of Sabah] is a very small fraction of what originally existed," said Benoit Goossens, a study co-author and wildlife geneticist at Cardiff University in Wales.
"If the decline continues at the same speed, the population will be extinct within a few decades."
Intertwined Genetic Records
Conservationists have long believed that orangutan declines in Indonesia and Malaysia are linked to habitat loss due to logging and the subsequent conversion of forests into oil-palm plantations.
But precisely measuring this connection via gene studies has been tricky.
One technique is to look at patterns of genetic variation in a population, which might provide a clue about that species history.
But the genetic structure of most species contains records of population fluctuations tied to eons of climate change and other factors. This makes it hard to flesh out a more recent record of decline or increase.
For their study, Goossens and his colleagues sampled DNA from the hair and feces of 200 wild orangutans in Malaysia's Kinabatangan Wildlife Sanctuary. The scientists found a pattern of genetic variation typical of decreasing populations.
The researchers then plugged their data into computer models and subtracted out the effects of hunting by early humans and climate change.
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