According to a study published in the journal PLoS Biology, two closely related great ape species — the bonobo (Pan paniscus) and the common chimpanzee (Pan troglodytes) — share not only the physical form of the gestures but also many gesture meanings.
Chimps and bonobos use gestures to initiate and change positions during grooming. Image credit: Catherine Hobaiter.
Chimpanzees and bonobos use gestures in a variety of different situations and for multiple purposes, such as to initiate and change positions during grooming.
These species are closely related, having separated about 1-2 million years ago, and scientists already know that they share many of the same gestures, but the degree of similarity between the meanings of the chimpanzee and bonobo gestures is a new discovery.
“The overlap in gesture meanings between bonobos and chimpanzees is quite substantial and may indicate that the gestures are biologically inherited,” said study first author Dr. Kirsty Graham, from the Department of Psychology at the University of York, UK.
In the study, Dr. Graham and co-authors from the University of St Andrews and Kyoto University first defined the meaning of each bonobo gesture by looking at the reaction that it elicits and whether the bonobo who gestured was ‘satisfied’ with the reaction.
If, for example, the first bonobo presents an arm in front of a second bonobo, the second bonobo responds by climbing onto the first bonobo’s back and the first bonobo then stops gesturing, the researchers infer that the first bonobo was satisfied, and therefore that the meaning of that single gesture is ‘climb on me.’
Taken over many observations, the team was able to systematically define the sets of meanings of 33 bonobo gesture types and compare them to gesture meanings already known for chimpanzees.
It appears that many gesture meanings are shared by both species, and perhaps may have also been shared by our last common ancestor.
“In future, we hope to learn more about how gestures develop through the apes’ lifetimes,” Dr. Graham said.
“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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K.E. Graham et al. 2018. Bonobo and chimpanzee gestures overlap extensively in meaning. PLoS Biol 16 (2): e2004825; doi: 10.1371/journal.pbio.2004825
