Human language evolved through gestures

Gestures were the building blocks on which human language evolved, according to the findings by a research team of Yerkes National Primate Research Center, Emory University.

Washington, May 1 : Gestures were the building blocks on which human language evolved, according to the findings by a research team of Yerkes National Primate Research Center, Emory University.

The team found bonobos and chimpanzees used manual gestures of their hands, feet and limbs more flexibly, compared to facial expressions and vocalizations, to express themselves.

The team worked with two groups of bonobos (13 animals) and two groups of chimpanzees (34 animals), to distinguish 31 manual gestures and 18 facial/vocal signals.

They found that while both species used facial/vocal signals similarly, but the same did not hold true for the manual gestures. Rather, both within and between species, the manual gestures were less closely tied to a particular emotion and, served a more adaptable function.

A single gesture could communicate an entirely different message depending upon the social context in which it is used, the researchers said.

"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. A scream, however, is a typical response for victims of intimidation, threat or attack. This is so for both bonobos and chimpanzees, and suggests that vocalization is relatively invariant," said Dr. Amy Pollick, a Yerkes researcher.

The scientists said a study of similar types of communication in closely related species revealed shared ancestry.

"We know gestures are evolutionarily younger than facial expressions and vocalizations, as shown by their presence in apes and humans but not in monkeys. A gesture that occurs in bonobos and chimpanzees as well as humans was likely present in the last common ancestor," said Pollick.

"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," said Frans de Waal, another Yerkes researcher.

The team further found that bonobos used gestures more flexibly than chimpanzees, and both engaged in multi-modal communication, combining their gestures with facial expressions and vocalizations to communicate a message.

"Different groups of bonobos used gestures in specific contexts less consistently than did different groups of chimpanzees. 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," said Pollick.

The findings appear in the current issue of the Proceedings of the National Academy of Sciences (PNAS).

ANI