Apes communicate with their own sign language, which can even differ between groups of the same kind. Photo: PNAS
Read aloud Great apes communicate with their own sign language, which can even differ between individual groups. An American researcher has found this out in the observation of several chimpanzee and bonobo groups. While facial expressions and tonal sounds are the same in both species, the use of gestures between the two species varied greatly. The results support the long-standing theory that gestures are the most original form of language and probably preceded human language ability, the researchers said. While all primates communicate with vocal sounds and facial expressions, only humans and apes use their limbs as a means of communication. The gestures in humans probably developed even before the spoken word and are therefore considered the origin of human language. How hands and feet are used exactly and how the other person reacts to such gestures is still largely unclarified.

The American research duo now observed two chimpanzee and bonobo groups each with a total of 47 animals. The biologists divided the hand and foot marks and the facial and sound signals into several classes and examined in which situation and with which purpose the monkeys used a certain sign. The researchers found that facial expressions and vocal sounds are strongly linked to their context and thus have approximately the same significance in both species. On the other hand, the monkeys used their hands and feet very flexibly, and the signals even differed between the groups of the same kind. The same hand gesture could therefore mean something completely different in another situation or within another group, while a scream, for example, always responded to a Attack or a threat, the scientists explain.

Interestingly, bonobos received a more frequent response from their peers when mimicking facial expressions, gestures, and vocal sounds, rarely using such combined signals. The miniature chimpanzees are likely to use the respective means of communication deliberately, rather than simply merge them rashly, the researchers said. The communication between bonobos is therefore likely to better characterize the communication between man's early ancestors, the scientists speculate. They now hope to be able to draw conclusions from the results on the origin of language in humans.

Amy Pollick & Frans de Waal (Emory University, Atlanta): PNAS, online pre-release, DOI: 10.1073 / pnas.0702624104 ddp / science.de? Claudia Hilbert ad

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