Connecting primate gesture to the evolutionary roots of language: A systematic review

Abstract

Comparative psychology provides important contributions to our understanding of the origins of human language. The presence of common features in human and nonhuman primate communication can be used to suggest the evolutionary trajectories of potential precursors to language. However, to do so effectively, our findings must be comparable across diverse species. This systematic review describes the current landscape of data available from studies of gestural communication in human and nonhuman primates that make an explicit connection to language evolution. We found a similar number of studies on human and nonhuman primates, but that very few studies included data from more than one species. As a result, evolutionary inferences remain restricted to comparison across studies. We identify areas of focus, bias, and apparent gaps within the field. Different domains have been studied in human and nonhuman primates, with relatively few nonhuman primate studies of ontogeny and relatively few human studies of gesture form. Diversity in focus, methods, and socio‐ecological context fill important gaps and provide nuanced understanding, but only where the source of any difference between studies is transparent. Many studies provide some definition for their use of gesture; but definitions of gesture, and in particular, criteria for intentional use, are absent in the majority of human studies. We find systematic differences between human and nonhuman primate studies in the research scope, incorporation of other modalities, research setting, and study design. We highlight eight particular areas in a call to action through which we can strengthen our ability to investigate gestural communication's contribution within the evolutionary roots of human language.

Intentional gestural communication amongst red-capped mangabeys (Cercocebus torquatus)

“…Due to this choice of markers, it conquers recent debates concerning the validity of using only one or a restricted set of markers when assessing animals’ intentional communication skills (see, e.g. Liebal et al 2013 ; Townsend et al 2017 ; Graham et al 2020 ; Ben Mocha and Burkart 2021 ; Rodrigues et al 2021 ). The different markers of intentionality jointly assess several aspects of both the communicative and goal-directed properties of socially produced behaviour, with each marker contributing its own added value to this assessment (Ben Mocha and Burkart 2021 ).…”

“…The different markers of intentionality jointly assess several aspects of both the communicative and goal-directed properties of socially produced behaviour, with each marker contributing its own added value to this assessment (Ben Mocha and Burkart 2021 ). Ideally, therefore, any study claiming that an animal’s apparently communicative behaviour is ‘intentional’ should clearly account for both the communicative and goal-directed aspects of this behaviour, by providing converging evidence for the use of as many markers of intentionality as possible (Liebal et al 2013 ; Townsend et al 2017 ; Graham et al 2020 ; Ben Mocha and Burkhart 2021 ) and providing as much detail as possible on their frequency and distribution of use (Rodrigues et al 2021 ; Ben Mocha and Burkart 2021 ).…”

Coordinating social action: A primer for the cross-species investigation of communicative repair

“…We use this framework to review existing evidence and exemplify it by analysing examples of video-recorded interactions of chimpanzees, bonobos and humans. In doing so, we hope our research framework can be used as a template to produce systematic, comparative data on joint action in nonhuman animal species, and contribute towards stronger empirical foundations for the cross-species investigation of communicative behaviour [15][16][17]. With more comparative evidence on interactional structures across species, we may be able to trace evolutionary continuities in strategies for the resolution of communicative trouble, and to assess the extent to which repair may be part of a human-unique foundation on which language has evolved [8].…”

Variable expression of linguistic laws in ape gesture: a case study from chimpanzee sexual solicitation

“…We included signaller ID, sequence ID, and gesture type as random effects. We include Category as a variable here to allow for more direct comparison with previous work, which often excludes or differentiates non-manual signals, either in great ape gesture (Heesen et al, 2019;Rodrigues et al, 2021) or in signed languages and fingerspelling (e.g., Börstell et al, 2016).…”