Abstract
A key challenge for primates living in large, stable social groups is managing social relationships. Chimpanzee gestures may act as a time-efficient social bonding mechanism, and the presence (homogeneity) and absence (heterogeneity) of overlap in repertoires in particular may play an important role in social bonding. However, how homogeneity and heterogeneity in the gestural repertoire of primates relate to social interaction is poorly understood. We used social network analysis and generalized linear mixed modelling to examine this question in wild chimpanzees. The repertoire size of both homogeneous and heterogeneous visual, tactile and auditory gestures was associated with the duration of time spent in social bonding behaviour, centrality in the social bonding network and demography. The audience size of partners who displayed similar or different characteristics to the signaller (e.g. same or opposite age or sex category) also influenced the use of homogeneous and heterogeneous gestures. Homogeneous and heterogeneous gestures were differentially associated with the presence of emotional reactions in response to the gesture and the presence of a change in the recipient's behaviour. Homogeneity and heterogeneity of gestural communication play a key role in maintaining a differentiated set of strong and weak social relationships in complex, multilevel societies.
Highlights
One of the most intriguing questions in the science of human origins involves the definition of language, its fundamental2017 The Authors
This study examines how the homogeneity of gestural repertoire and heterogeneity of gestural repertoire are related to social bonds of wild chimpanzees, measured by the duration of social bonding behaviours per hour pairs of chimpanzees spend in the same party
We examined the influence of these factors on dyadic and group-level homogeneity and heterogeneity in the gestural repertoire in the Sonso group of wild East African chimpanzees (Pan troglodytes schweinfurthii) in Budongo Forest, Uganda, Africa
Summary
One of the most intriguing questions in the science of human origins involves the definition of language, its fundamental2017 The Authors. Viewed as a system of 2 cognition and communication, one key selection pressure for the evolution of language may have been to facilitate social bonding and group cohesion in increasingly large groups of hominins [7,8]. Because language and accent are inseparable from the person and difficult to falsify, they may have been an important social marker through the course of human evolution, facilitating the development of ‘tag-based’ cooperation across increasingly large and dispersed social groups [9,11,14,15]. Examining how repertoire homogeneity in non-human primates relates to social bonding can provide insights into the importance of overlap in communication repertoire in facilitating both dyadic interactions and large-scale sociality through the course of hominin evolution [15]
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