KEY POINTS:
The hand gesturing of politicians can be traced back to signals used by our ape-like ancestors, says a study into how chimpanzees communicate with one another.
Apes and humans share the ability to communicate with their limbs as well as their vocal cords, and scientists now 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 manual gestures among chimpanzees and bonobos, a closely related species of pygmy chimp, and found that they used movements of arms and legs in their communication repertoire.
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 that they shared with humans.
"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 two scientists say in their study published 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 the apes used 31 manual gestures and 18 facial or vocal signals to communicate.
One of the main findings was 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, depending on the context and who in the troupe was involved.
"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.
"A gesture occurring in bonobos and chimpanzees as well as humans is likely to have been present in the last common ancestor.
"A good example of a shared gesture is the open-hand begging gesture used by both apes and humans.
"This gesture can be used for food, if there is food around, but it also can be used to beg for help, for support, for money and so on. It's meaning is context dependent."
The study found that bonobos used manual 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 human ancestors were developing language, which even today is often used alongside hand gestures to emphasise a point or explain an argument.
- INDEPENDENT
