Threat Vocalisations are Acoustically Similar between Humans (Homo sapiens) and Chimpanzees (Pan troglodytes)

Abstract

In behavioural contexts like fighting, eating, and playing, acoustically distinctive vocalisations are produced across many mammalian species. Such expressions may be conserved in evolution, pointing to the possibility of acoustic regularities in the vocalisations of phylogenetically related species. Here, we test this hypothesis by examining the degree of acoustic similarity between human and chimpanzee vocalisations produced in 10 equivalent behavioural contexts. We use two complementary analysis methods: Pairwise acoustic distance measures and acoustic separability metrics based on unsupervised learning algorithms. Acoustic features of vocalisations produced when threatening another individual were distinct from other types of vocalisations and highly similar across species. Using a multimethod approach, these findings demonstrate that human vocalisations produced when threatening another person are acoustically similar to chimpanzee vocalisations in the same situation, likely reflecting a phylogenetically ancient vocal signalling system.