Chimps & Bonobos Share Common Gestures, Researchers Find

Chimpanzees and bonobos use gestures to initiate and change positions during grooming. (Catherine Hobaiter)

(CN) – Bonobos and chimpanzees can probably understand each other’s gestures, a new study finds.

While researchers already know that the two great ape species, which are closely related to humans and each other, share many of the same gestures, the level of similarity between the meanings of their signals is a new finding, according to a report published Tuesday in the journal PLOS Biology.

“Cross-species comparison of great ape gesturing has so far been limited to the physical form of gestures in the repertoire, without questioning whether gestures share the same meanings,” the report states. “Researchers have recently cataloged the meanings of chimpanzee gestures, but little is known about the gesture meanings of our other closest living relative, the bonobo.

“The bonobo gestural repertoire overlaps by approximately 90 percent with that of the chimpanzee, but such overlap might not extend to meanings. Here, we first determine the meanings of bonobo gestures by analyzing the outcomes of gesturing that apparently satisfy the signaler.”

For example, if the signaler presents an arm in front of another bonobo, the second bonobo responds by climbing onto the signaler’s back, who then stops gesturing. The authors would interpret from such an interaction that the signaler was satisfied, and that the meaning of the gesture is “climb on me.”

After recording numerous interactions, the team was able to systematically define the sets of meanings of 33 bonobo gestures and compare them to the meanings of signals already known for chimps.

The authors found that the species share many gesture meanings, which may have also been shared by our last common ancestor, fittingly referred to as the chimpanzee-human last common ancestor.

“The overlap in gesture meanings between bonobos and chimpanzees is quite substantial and may indicate that the gestures are biologically inherited,” says lead author Kirsty Graham, a research associate at the University of York in Great Britain. “In the future, we hope to learn more about how gestures develop through the apes’ lifetimes.

“We are also starting to examine whether humans share any of these great ape gestures and understand the gesture meanings, so watch this space.”

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