Higher fundamental frequency in bonobos is explained by larynx morphology

Acoustic signals, shaped by natural and sexual selection, reveal ecological and social selection pressures [1]. Examining acoustic signals together with morphology can be particularly revealing. But this approach has rarely been applied to primates, where clues to the evolutionary trajectory of huma...

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Bibliographic Details
Published in:Current biology 2018-10, Vol.28 (20), p.R1188-R1189
Main Authors: Grawunder, Sven, Crockford, Catherine, Clay, Zanna, Kalan, Ammie K., Stevens, Jeroen M.G., Stoessel, Alexander, Hohmann, Gottfried
Format: Article
Language:English
Subjects:
Acoustics
Animals
Larynx - anatomy & histology
Pan paniscus - anatomy & histology
Pan paniscus - physiology
Pan troglodytes - anatomy & histology
Pan troglodytes - physiology
Species Specificity
Vocalization, Animal
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Summary:Acoustic signals, shaped by natural and sexual selection, reveal ecological and social selection pressures [1]. Examining acoustic signals together with morphology can be particularly revealing. But this approach has rarely been applied to primates, where clues to the evolutionary trajectory of human communication may be found. Across vertebrate species, there is a close relationship between body size and acoustic parameters, such as formant dispersion and fundamental frequency (f0). Deviations from this acoustic allometry usually produce calls with a lower f0 than expected for a given body size, often due to morphological adaptations in the larynx or vocal tract [2]. An unusual example of an obvious mismatch between fundamental frequency and body size is found in the two closest living relatives of humans, bonobos (Pan paniscus) and chimpanzees (Pan troglodytes). Although these two ape species overlap in body size [3], bonobo calls have a strikingly higher f0 than corresponding calls from chimpanzees [4]. Here, we compare acoustic structures of calls from bonobos and chimpanzees in relation to their larynx morphology. We found that shorter vocal fold length in bonobos compared to chimpanzees accounted for species differences in f0, showing a rare case of positive selection for signal diminution in both bonobo sexes. Grawunder et al. show that Bonobo males and females have loud calls with nearly double the fundamental frequency and half the vocal length of those of their sister species, the chimpanzee.
ISSN:0960-9822
1879-0445
DOI:10.1016/j.cub.2018.09.030