Grooming is not the only regulator of primate social interactions

Language as a tool for social bonding: evidence from wild chimpanzee gestural, vocal and bimodal signals

The evolution of language has fascinated anthropologists, psychologists and biologists for centuries, seeking to infer language origins from the communication of primates, our closest living relatives. Capacity for intentional signalling is a key feature of transition to language in our hominin ancestors, facilitating complex social dynamics in complex social groups. However whether vocal, gestural and bimodal signals are differentiated according to intentional use and hence complex sociality has not been studied, making unclear the modality of language evolution. We addressed this question in wild chimpanzees. We found that larger social network size was associated with a larger network of gestural but not vocal or bimodal signals. Response waiting was more common in association with gestures than vocalizations, but elaborations were more common in vocal than gestural or bimodal signals. Overall, chimpanzees were more likely to manage weak social bonds through vocalizations, whereas strong social bonds were managed through gestures and bimodal signals. However, when social bonds were weak, gestures accompanied by response waiting were more likely to elicit approaches than vocalizations accompanied by elaboration, which elicited avoidance. This suggests that gestures were the primary modality of language evolution and that the use of more sophisticated gestural signalling led to evolution of complex social groups of hominin ancestors. This article is part of the theme issue 'Cognition, communication and social bonds in primates'.

Neocortical size and language

In my target article, I argued (1) that the relationship between neocortical size and group size in primates implies that there is a cognitive limit on the size of human groups, and (2) that time constraints forced the evolution of language as a more efficient means of bonding the large groups that humans evolved. The doubts about these claims raised by these additional commentaries largely reflect misinterpretation of my original claims.

Does language arise from a calculus of dominance?

Robin Dunbar's hypothesis that language capacity in response to the demands of maintaining large groups suggests a more specific hypothesis that language arose from a cognitive calculus by which animals could predict their status in complex dominance situations.

Another far more ancient tongue

Language started evolving early, before gesture; commonalities of generativity between language and praxis have been over-emphasized. Language did not drive hominid brain evolution, evolving multifactorially and interactively. More than communication, it permits a cognitive modelling of reality and hierarchical data management. As the interactive sum of various cognitive and linguistic systems, and of brain structures each semi-independently evolved, it is not part of a single, general-purpose cognitive processor, nor is it a separately-evolved quasi-independent module.

The origin of language: More words needed

Dunbar's idea that neocortex size limits the number of relationships beings may be able to maintain is an engaging hypothesis for cognitive psychologists interested in a limited capacity model. It is suggested that the thesis would have been enhanced had the author considered the concept of peers as part of an information processing scheme.