Evidence of learned social behaviour provides glimpse of human evolution
By ANNE MCILROY
SCIENCE REPORTER
Friday, January 3, 2003 - Print Edition, Page A3
They use leaves as napkins to wipe their hairy faces and blow goodnight "raspberries" to each other as they bed down for the night. It may not be high culture, but researchers say wild orangutans have learned social behaviours that make up an animal culture that was likely a precursor to our own.
The scientists, including Canadian Birutè Galdikas, have all spent years, and in some cases decades, studying orangutans in the wild.
They reached the conclusion that orangutans have developed culture after meeting last year to compare data on the behaviour of the primates at six sites in Indonesia and Malaysia. Their findings were published in today's edition of the prestigious journal Science.
Carel van Schaik of Duke University, who has studied orangutans for 26 years, said that humans and orangutans are both technically great apes. This means, he said, that orangutan culture is the foundation on which human culture is built.
"They allow us to study our own past," he said in an interview. "Human culture didn't just arise de novo, but reaches far back in evolutionary time."
The researchers say their findings push back the origins of culturally transmitted behaviour to 14 million years ago, when orangutans first evolved from their primate ancestors.
By definition, cultural traits should vary from region to region and should not depend on habitat. These orangutans lived in similar habitats and had access to the same kinds of food, but each group displayed distinct regional habits.
Orangutans in Kutai, Borneo, used leaves as napkins to wipe sticky fruit residue off their fur, while those in Sumatra blew raspberries every night as they climbed into their tree nests so loud they could be heard 15 metres away.
In Tanjung Puting, Borneo, the apes play a sport that resembles bungee jumping. The animals would ride falling dead trees, but grab a vine or other vegetation to escape before the tree hit the ground. Researchers call it snag riding.
And while it certainly couldn't be classified as music, the members of each group made distinct variations of a noise the researchers describe as "kiss-squeaks", a sort of mouth fart made either into the air or amplified with a hand or a leaf.
The scientists had previously believed the traits they observed in the individual populations were common to all orangutans. But at last year's meeting, they discovered there were dramatic differences between the groups.
It was these differences that led researchers to the conclusion that the behaviours were evidence of cultural learning, passed down from generation to generation.
Further analysis showed these behaviours tended to be observed in more than one group only when the animals had a chance of running into each other, Dr. van Schaik said.
For years, researchers believed culture, or the ability of a group to adopt new behaviours and pass them on the next generation, was uniquely human. In 1999, chimpanzee researchers concluded there was such a thing as chimp culture using the same method of comparing field data.
But Dr. van Schaik said the orangutan scientists hadn't expected to come to a similar conclusion because orangutans are much less social than chimps.
"Culture requires more than just a mother-infant bond, but also extensive social contact, and orangutans are at the low end of the sociability spectrum. They are more independent than chimps," he said.
Previously, researchers had estimated that culture first evolved with the chimps seven million years ago.