Bonobo and chimpanzee gestures overlap extensively in meaning
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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. Researchers have recently catalogued 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% with that of the chimpanzee, but such overlap might not extend to meanings. Here, we first determine the meanings of bonobo gestures by analysing the outcomes of gesturing that apparently satisfy the signaller. Around half of bonobo gestures have a single meaning, while half are more ambiguous. Moreover, all but 1 gesture type have distinct meanings, achieving a different distribution of intended meanings to the average distribution for all gesture types. We then employ a randomisation procedure in a novel way to test the likelihood that the observed between-species overlap in the assignment of meanings to gestures would arise by chance under a set of different constraints. We compare a matrix of the meanings of bonobo gestures with a matrix for those of chimpanzees against 10,000 randomised iterations of matrices constrained to the original data at 4 different levels. We find that the similarity between the 2 species is much greater than would be expected by chance. Bonobos and chimpanzees share not only the physical form of the gestures but also many gesture meanings.
Graham , K E , Hobaiter , C , Ounsley , J , Furuichi , T & Byrne , R W 2018 , ' Bonobo and chimpanzee gestures overlap extensively in meaning ' PLoS Biology , vol 16 , no. 2 , e2004825 . DOI: 10.1371/journal.pbio.2004825
© 2018 Graham et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: JSPS Core-to-Core Program http://www.jsps.go.jp/english/e-core_to_core/ (grant number 2012-2014, 2015-2017). Japan Society for the Promotion of Science Grant in Aid for Scientific Research (grant number 25304019, 25257407, 26257408). University of St Andrews https://www.st-andrews.ac.uk/study/ug/fees-and-funding/scholarships/600th-wardlaw/ (grant number 600th Anniversary Scholarship). Wenner-Gren Foundation http://www.wennergren.org/ (grant number Gr. 8950).
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