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Much as we might preferred in the world of radios, speech is not the only way to communicate. There are also waves, and handshakes, and the finger. Researchers at Emory University is studying how language evolved by observing the way that apes used gestures.
Michelle Trudeau reports.
MICHELLE TRUDEAU: Watch a group of apes for a while, you'll inevitably see them gesturing using their hands to communicate that they want something from another, like food or to play or to be groomed or to have sex. Researchers Frans de Waal and Amy Pollick studied gestures in two groups of chimps and two groups of bonobos. Just to clarify, chimps and bonobos are two separate species of apes. Genetically, they are human's closest relatives. So the researchers video taped hundreds of hours of the chimps and bonobos, which revealed that these primates used over 30 distinct gestures like waving a hand, raising an arm, dabbing with the finger, reaching out. The researchers linked each gesture with the context of what was going on at the moment.
Here's primatologist Frans de Waal.
Mr. FRANS DE WAAL (Primatologist, Emory University): So for example, someone has food. Let's say some other chimp has a pineapple.
TRUDEAU: And the second chimp approaches and extends an open hand.
Mr. DE WAAL: The open hand begging gesture is also a universal human gesture used for begging for money and for food. And the apes used that in that particular context to beg for food.
TRUDEAU: But in a different context, the open hand gesture conveys something totally different.
Mr. DE WAAL: So let's say I have a fight with you and my best friend is coming around the corner and I go to my best friend and I hold out the open hand. In that case, it seems to mean like why don't you come help me? And so the same gesture can be used for very different reasons.
TRUDEAU: The apes in the study also started using an old gesture in a completely novel situation.
Mr. DE WAAL: So for example, the bonobos, they clap their hands sometimes while they groom each other. There are no other bonobos in the world that I know of who do that.
TRUDEAU: And de Waal adds if one ape starts using a gesture in a unique context, others in the group are apt to copy it, leading to what's called cultural transmission, like the group develops its own dialect of gestures.
Mr. DE WAAL: In the chimpanzees, we have one group - not the other, just one group - where the chimpanzees hold hands, two hands together, above their heads, when they groom each other with the other hand. It's a very strange posture. It was developed by one female named Georgia and she introduced her family members to it, and now all the chimps in the group are doing it.
TRUDEAU: The researchers also compared gestures with two other ways that apes communicate, through vocalizations and facial expressions, and found that only gestures varied between the four groups and between the two species. Vocalizations and facial expressions were pretty much fixed. So for example, a particular vocalization like a pant hoot was used by all four groups in the same kind of situation. So the point is gestures are flexible. Apes used them to communicate different things in different situations.
Language researcher Susan Goldin-Meadow from the University of Chicago finds this flexibility intriguing. It suggests that gestural communication may be a precursor to human language.
Ms. SUSAN GOLDIN-MEADOW (Language Researcher, University of Chicago): These species can be modifying their gestures and perhaps teaching their gestures to one another or learning their gestures, so that it has a sort of flexibility that might allow the communication system to grow ahead of it. It looks like it may be the beginning.
TRUDEAU: Spoken language in humans is infinitely flexible, she says. So the flexibility of gestures may be the first primitive step toward the evolution of human language. The research appears in the current of the proceedings of the National Academy of Sciences.
For NPR News, I'm Michelle Trudeau.
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