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How politicians ape their primate ancestors

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By Steve Connor, Science Editor – The Independent 01 May 2007

The hand gesturing of politicians can be traced back to the manual signals first used by our ape-like ancestors, according to a study into how chimpanzees communicate with one another.

Apes and humans both share the ability to communicate with their limbs as well as their vocal cords and scientists believe it may be the result of a common origin that evolved millions of years before the development of language. It could explain why politicians like to emphasise a point with a clenched fist, explain a failed policy with an upturned palm or bat away an unpleasant question with a raised hand.

The study looked at gestures among chimpanzees and bonobos, a closely related species of pygmy chimp, and found they both used movements of arms and legs to communicate.

Amy Pollick and Frans de Waal, of Yerkes National Primate Research Centre at Emory University, in Atlanta, Georgia, believe both species acquired the gestures through a common ape ancestor. “The natural communication of apes may hold clues about language origins, especially because apes frequently gesture with limbs and hands, a mode of communication thought to have been the starting point of human language evolution,” the scientists say in their study in the journal, Proceedings of the National Academy of Sciences.

The researchers studied two groups of chimps and two groups of bonobos – 47 individuals in total – and found that the apes used 31 manual gestures and 18 facial or vocal signals to communicate. They found that vocal calls such as a scream were closely tied to a particular emotion whereas hand or limb gestures were used in a looser manner. “A chimpanzee may stretch out an open hand to another as a signal for support, whereas the same gesture toward a possessor of food signals a desire to share,” said Dr Pollick. “A scream, however, is a typical response for victims of intimidation, threat or attack. This is so for both bonobos and chimpanzees, and suggests the vocalisation is relatively invariant.”

Monkeys – a primate group that diverged from apes much earlier – do not show any of the sophisticated hand gestures seen in chimpanzees and bonobos, which suggests that manual gesturing is relatively recent.

“A gesture that occurs in bonobos and chimpanzees as well as humans is likely to have been present in the last common ancestor,” said Dr Pollick. “A good example of a shared gesture is the open-hand begging gesture. This gesture can be used for food but it also can be used to beg for help, for support and so on.”

Bonobos used gestures in a more flexible manner and were able to combine different gestures with various vocal calls to communicate in a wider context. The researchers suggested this could be what happened when our early ancestors were developing language. “Different groups of bonobos used gestures in specific contexts less consistently than did different groups of chimpanzees,” said Dr Pollick. “While chimpanzees produce more of these combinations, bonobos respond to them more often. This finding suggests the bonobo is a better model of symbolic communication in our early ancestors.”

Written by huehueteotl

May 1, 2007 at 10:40 am

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