Scientists look to apes for language origin clues

By Will Dunham

WASHINGTON (Reuters) - A male chimpanzee may beg for food from another chimpanzee by gesturing with an extended arm and open hand.

Under different circumstances, the same chimpanzee may use the same gesture to try to coax a female chimpanzee to have sex. And the same gesture may be used after two males fight as a signal of reconciliation.

In research published on Monday, scientists seeking clues to the origins of human language analyzed the way two types of apes genetically closely related to people -- chimpanzees and bonobos -- use such hand and limb gestures to communicate.

They found that the apes use such gestures much more flexibly -- in different contexts with apparently different meanings -- than they used facial expressions and vocalizations. The findings, they believe, lend support to the idea that human language started with such gestures rather than speech.

"We are a naturally gesturing species that may have first developed language in the gestural domain, and once the brain parts related to language were well developed, then started using speech," primatologist Frans de Waal of Emory University and Yerkes National Primate Research Center in Atlanta said in a telephone interview.

De Waal conducted the study, published in the Proceedings of the National Academy of Sciences, with fellow Yerkes researcher Amy Pollick, who observed and videotaped 13 bonobos at the San Diego Zoo and 34 chimpanzees at Yerkes.

De Waal and Pollick tallied 31 hand and limb gestures and 18 facial expressions and vocalizations. Both types of apes used facial and vocal signals in similar and predictable ways. Screaming was used by both, for example, in fear and pain.

But a particular gesture appeared to communicate wholly different messages depending on the social context in which it was used -- for example if food was involved or mating.