Bonobo and chimpanzee gestures share multiple meanings

Chimpanzees and bonobos use gestures in a variety of different situations and for multiple purposes, such as to initiate and change positions during grooming.

The two species separated approximately 1-2 million years ago, and although it is already known that they share many of the same gestures, the degree of similarity between the meanings of the chimpanzee and bonobo gestures is a new discovery.

Published in PLOS Biology, researchers from the Universities of York, St Andrews, and Kyoto 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.

Dr Kirsty Graham, Research Associate at the University of York's Department of Psychology, said: "The overlap in gesture meanings between bonobos and chimpanzees is quite substantial and may indicate that the gestures are biologically inherited."

The team observed various behaviors such as a bonobo presenting its arm in front of a second bonobo; the second bonobo would respond by climbing onto the first bonobo's back. The first bonobo then stops gesturing, suggesting the reaction from the second bonobo was the correct one.

From this the researchers were able to infer that this single gesture meant "climb on me."

Taken over many observations, the researchers were 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.

Dr Graham said: "In 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."