From the dainty use of a leaf as a napkin to saying goodnight with a lip-quivering raspberry splutter, the orangutan is a cultured ape, able to learn new tricks and pass them along to the next generation, researchers say.
The discovery suggests that early primates, which include the ancestors of humans, may have developed the ability to invent new behaviors, such as tool use, as early as 14 million years ago, some 6 million years earlier than once believed.
“If the orangutans have culture, then it tells us that the capacity to develop culture is very ancient,” says Birute Galdikas, a co-author of a study appearing this week in Science.
In the march of evolution, “orangutans separated from our ancestors and from the African apes many millions of years ago,” she said, and the new study suggests “they may have had culture before they separated.”
Culture, in the scientific sense, is the ability to invent new behaviors that are adopted by the population group and are passed along to succeeding generations. Orangutan culture is crude by human standards, but it is culture nonetheless because it is developed and practiced independently by different groups and succeeding generations in the same way that human societies develop and perpetuate unique forms of music, architecture, language, clothing and art.
Mr. Galdikas, a researcher at the Orangutan Foundation International, and eight other international primate scientists analyzed years of observations of the shy Southeast Asian orangutan and concluded the ape definitely has the ability to adopt and pass along learned behaviors.
The researchers studied results from observations of six widely separated bands of orangutans in Borneo and Sumatra and found that each group practiced unique behaviors.
For instance, members of bands in Borneo and Sumatra make a kiss-squeak noise by compressing the lips and drawing in air. Both groups used leaves to amplify the noise, but only the Borneo group had discovered they could change the sound by cupping the hands over the mouth. The sounds are apparently used for communicating socially. None of the other groups demonstrated this skill.
The opposite of the kiss-squeak is the raspberry breath is blown out through compressed lips to make a splattering sound. Only one of the six groups does this habitually and it seems to be related to a bedtime ritual, Mr. Galdikas said.
A group in Sumatra has learned to use leaves as gloves when handling spiny fruits. None of the others has discovered this yet. Another Sumatra band has learned the unique skill of getting a drink by dipping a leafy branch into a water-filled tree hole and then licking the moisture from the leaves.
Mr. Galdikas said a group in Borneo routinely will force a small tree to the ground, riding it as it falls, grabbing nearby forest limbs before crashing to the ground. Another group, in Sumatra, uses the same technique as a defensive maneuver, pushing over tree snags when they feel threatened.
“They almost got me once doing that,” Mr. Galdikas noted.
Only a single group of the six has discovered how to use sticks to extract insects from tree holes or to wedge out seeds from fruits. Such tool use is common among chimpanzees, but the Sumatra orangutan band puts a unique twist on the practice they grip the stick with their teeth instead of their hands.
The dainty use of a napkin has been discovered by one band. Apes in a Borneo band routinely wipe their faces with leaves and parents teach the social skill to their young.