Home Sciences Chimpanzees “speak” almost like humans

Chimpanzees “speak” almost like humans

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Wild chimpanzees use some 400 “words” to communicate with each other, forming a kind of incomplete language quite similar to human language, although we still don’t know what they mean.

Humans are the only species on earth known to use language. We do this by combining sounds to form words and words to form hierarchically structured sentences. The question, how this extraordinary ability originates, still remains to be answered.

To trace the evolutionary origins of human language, researchers often use a comparative approach: They compare the vocal production of other animals, particularly primates, with that of humans.

Unlike humans, nonhuman primates often use individual calls, of different types, and rarely combine them together to form vocal sequences. Consequently, vocal communication in nonhuman primates appears much less complex than human communication.

human complexity

However, the complexity of human language does not arise from the number of sounds we use when we speak, which is generally less than 50 different sounds in most languages, but from the way we combine sounds in a structured way to form words. and we hierarchically combine these words to form sentences: thus we express an infinite number of meanings.

In fact, non-human primates also use up to 38 different calls to communicate, but they rarely combine them with each other. However, since they have not been analyzed in great detail so far, we may not have a complete picture of the structure and diversity of vocal sequences produced by non-human primates.

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Thousands of vocalizations

Researchers from the Max Planck Institutes for Evolutionary Anthropology and Brain and Cognitive Sciences in Leipzig, and the CNRS Institute for Cognitive Sciences in Bron, Lyon, France, recorded thousands of vocalizations produced by members of three groups of wild chimpanzees in the Taï National Park in Côte d’Ivoire. They identified 12 different types of calls and evaluated how chimpanzees combine them to form vocal sequences.

“Observing animals in their natural social and ecological environment reveals previously undiscovered complexity in the ways they communicate,” says the first author. Cedric Girard-Buttoz.

“Syntax is a hallmark of human language, and understanding how nonhuman primate vocalizations are structured is crucial to elucidating the origin of this human ability,” he adds. Emiliano Zaccarellaanother of the study’s authors.

Hundreds of “words”

The study shows that chimpanzees communicate with each other through hundreds of different sequences, combining up to ten types of calls in the entire repertoire. This is the first documentation of such diversity of vocal production in nonhuman primates.

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Furthermore, the researchers show that the calls, in combination with other specific calls, occurred predictably at certain positions in the sequence, following adjacency rules. These adjacency rules were also applied to sequences with three types of calls.

“Our findings highlight a vocal communication system in chimpanzees that is much more complex and structured than previously thought,” he explains. Tatiana Bortolatowho recorded the vocalizations in the forest.

wild complexity

“This is the first study in a larger project. By studying the rich complexity of vocal sequences in wild chimpanzees, a socially complex species like humans, we hope to provide a new perspective for understanding where we came from and how our unique language evolved.” Catherine Crockfordlead author of the study.

The authors will investigate what these complex and structured vocal sequences mean and whether they allow chimpanzees to increase the range of topics on which they can communicate.

Reference

Chimpanzees produce diverse vocal sequences with ordered and recombinatorial properties. Cédric Girard-Buttoz et al. Communications Biology, Volume 5, Article number: 410 (2022). DOI:https://doi.org/10.1038/s42003-022-03350-8

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