Getting a Hand on Language

How wild chimpanzees use basic sign language familiar to any human

  • Roger Di Silvestro
  • May 01, 2007
HAVE YOU EVER extended an open hand to another person in a gesture that says "please give me that"? If so, then you speak chimpanzee.

A new study of captive chimpanzees and bonobos (similar but smaller apes also called pygmy chimpanzees) has found that the two animals communicate through hand gestures, as does their closest living relative, the human. Probably all three species inherited this behavior from a common ancestor (humans split off from chimps about 5.4 million years ago, according to DNA studies, and bonobos split from chimps about 2.5 million years ago).

Conducted by researchers at the Yerkes National Primate Research Center at Emory University in Atlanta, Georgia, the study suggests that hand signals (which the scientists elegantly call "brachiomanual gestures"), rather than vocalizations, were the basis of early language.

In fact, in these apes, vocalizations seem much more fixed than do gestures. Both species used the same vocal expressions in the same context and with the same facial expressions. For example, a scream always indicates that a chimp or bonobo is frightened. In contrast, the meaning of hand gestures varies with the contexts in which they are used. A hand extended by one chimp toward another that has food means give me some of that, while a chimp in danger may extend an open hand to another chimp to say help me out here, I'm in trouble. The fixed nature of vocalizations suggests that in the two apes, sounds may be biologically programmed rather than under conscious control, as gestures appear to be.

The study, which included 13 bonobos in two groups and 34 chimpanzees in two groups, identified 31 hand signals--no, let's make that brachiomanual gestures--and 16 facial/vocal signals, or orofacial movements and vocalizations, as the scientists would say (try expressing that with a hand signal). The bonobos showed more variability in their use of specific hand signals than did chimps and were more likely than chimps to respond to gestures. Moreover, the bonobos used hand and arm gestures to underscore vocal and facial communications, much in the way that a human might say "I will not do that" while slamming a fist down on a tabletop.

Different groups of bonobos also developed different meanings for some gestures and passed these on to one another, suggesting that in the wild, chimps and bonobos from different regions might communicate in different hand dialects.

One primatologist has suggested that in humans, hand gestures were replaced by vocal language in response to increasing tool use, which would have tied up the hands as a form of communications media.

So, what does this have to do with your life personally? Well, the next time you inadvertently cut off another driver on the highway, and that driver responds to you with a certain well-known hand signal, tell yourself that you're not being insulted. No, you're just seeing someone get in touch with his or her inner ape.

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