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The behavior of bonobos, our closest primate relatives, is an important source of information about humans. Why are they so interesting to scientists? First of all, communication and sexual practices, say British psychologists and anthropologist Vyacheslav Ivanov.
Bonobos communicate with each other almost like human children – with the help of screams on a high note (“peep”), the meaning of which depends on the context.
Sometimes bonobos call “peep” very briefly, on a high note and with their mouths closed. They make these sounds in a variety of situations – pleasant, unpleasant or neutral. Researchers from the School of Psychology at the University of Birmingham (UK) studied the characteristics of these calls and found that acoustically the calls do not differ in neutral and joyful situations – for example, monkeys cry the same way during food, travel and rest. “Beeps” made in unpleasant or dangerous situations – with manifestations of aggression or the appearance of predators – are more like typical primate calls: their acoustic structure depends on the emotional state of the monkey.
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“While studying bonobos in their natural habitat in the Congo, I was struck by how often and in how many different situations they make “peep” sounds. It became clear that, since one “peep” is usually indistinguishable from another, it is required to understand the context of the situation in which the monkey screams, ”says study leader Zanna Clay (Zanna Clay)1. It is generally believed that in primates each type of cry is associated with a certain emotional state, and in humans, many of the sounds made are independent of such factors. Infants who have not yet learned to speak make special sounds called protosounds, or protophones, which are independent of their emotional state. These cries are different from typical sounds such as laughing or crying, as well as from the cries of most animals, which are thought to be made only in certain contexts.
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“We thought that it was premature to say that such sounds are characteristic only for humans, since no one has seriously studied similar calls in monkeys. But the more we explore this issue, the more we find in common between humans and animals,” says Zanna Clay.
This type of communication in wild bonobos may be evidence of an important evolutionary transition from “functionally fixed sounds” (tied to a specific context or emotional state) to human-type auditory communication. Such a transition probably occurred 6-10 million years ago in the common ancestors of bonobos and humans.
Gorillas, chimpanzees, bonobos, zoology or anthropology. A fragment of a lecture by Academician Vyacheslav Ivanov, delivered at the Russian State University for the Humanities in the summer of 2014.
Sexual symbolism in bonobo monkeys. A fragment of a lecture by Academician Vyacheslav Ivanov, delivered at the Russian State University for the Humanities in the summer of 2014.
1 Z. Clay et al. «Functional flexibility in wild bonobo vocal behaviour», PeerJ, August 2015.