Evolution of Primate Vocal Repertoires: Vocalization Systems as Embodied Capital for Mediating Within-group Conflict

Phylogenetic studies of communication help us understand evolutionary changes that led to human language – a form of primate communication, extraordinarily complex in terms of its varied vocalizations. Here we describe the macro-evolutionary role of life history traits on primate vocalization systems, informing our understanding of the relationships between social complexity and primate vocal repertoire size. We reviewed the primatological literature and collected information on the vocal repertoire size, social conflict, group size, endocranial volume, and maximum longevity of 42 non-human primate species. We conducted a set of analyses to examine the role of these factors on the macroevolution of vocal repertoire size over the course of primate evolution. Overall, the results strongly suggest that the embodied capital needed to support larger vocal repertoires has been selected for among anthropoid primates, especially hominoids. Large vocal repertoires help species cope with challenges of within-group conflict and cooperation that increase where larger groups have evolved with longer lifespans. While monkeys and apes developed substantially greater vocal complexity during the Late Miocene and the Early Pliocene, human language likely did not emerge until quite late in the primate evolutionary timeline, subsequent to the evolution of early hominins.