Tuesday, August 28, 2007
Chimps, baboons, use hands to communicate
"A study of how baboons gesture with their hands suggests gesturing may have been a precursor to human language, scientists say.
The findings could help to explain why humans often gesture with their hands, and particularly the right hand, when they speak.
The right hand is controlled by the brain's left hemisphere, which is the source of most linguistic functions.
Scientists believe communication by hand probably existed in apes 30 million years ago and was a forerunner to spoken and written language.
French researchers Adrien Meguerditchian and Professor Jacques Vauclair studied a particular hand gesture in 60 captive baboons.
The gesture consists of quick and repetitive rubbing or slapping of the hand on the ground, and is used to threaten or intimidate others.
The researchers, from the University of Provence, say this motion "might be comparable in humans to the slap of ... one hand toward the palm of the other hand".
For the study, which is published in the journal Behavioural Brain Research, the researchers observed this gesture as it occurred naturally.
They also triggered it by having a human abruptly shake his head and then glance at a baboon. Head shaking is another threatening move in the ape and monkey world, which includes all sorts of communicative gestures.
"A nonhuman primate can effectively raise an arm to ask a social partner to groom it ... give another a little slap as an invitation to play, touch furtively the hand or genitals of another to greet it, slap the ground to threaten," the researchers say.
Among the baboons in the test group that favoured a certain hand, 78% were right-handed and tended to gesture with this hand. Other studies have shown that most human babies and deaf individuals also communicate with their right hands.
"There is little chance that our [primate] cousins will evolve language skills in the near future," the researchers say.
"Monkeys and apes and their specific communication systems result from other evolutionary roads than those of humans ... It is very unlikely that the natural selection for primate species will reproduce exactly the same phylogenetic path that gave linguistic skills to humans."
William Hopkins, a US psychology professor at Berry College and an expert on the evolution of brain development in primates, says:
"I agree with the findings and think this is a very good and interesting paper. In many ways the results are nearly identical to those we have previously found in chimpanzees."
He explains that both chimps and baboons seem to use right-hand gestures for communication. This suggests the brain is asymmetrical when it comes to language, meaning that the left hemisphere tends to dominate.
"It will be interesting to see whether the asymmetries in hand use seen in the baboon link at all to brain asymmetries as we have found in the chimpanzees," Hopkins adds.
Source: News in Science
Posted by h.l. at 3:02 AM