11.05.2021 Andrea Ravignani

Understanding the origins and evolution of human speech and musical rhythm requires multidisciplinary approaches. One approach consists in investigating animals’ capacities for sound production, and its recently hypothesized link to rhythm cognition. In particular, the function, ontogeny, mechanisms and phylogeny of flexible vocal production in other animals can elucidate early stages of vocal production and rhythm cognition in the human lineage. Historically, comparative animal work in speech and music has been performed on either non-human primates or birds. However, at least four other taxonomic groups show greater phylogenetic proximity to humans than birds, and more developed vocal and rhythmic capacities than primates. These groups are pinnipeds (true seals, sea lions, fur seals, and walrus), bats, cetaceans, and elephants. Here I focus on pinnipeds and argue that, although this research lags decades behind avian and primate work, pinniped research has much to offer to understand the origins of human speech and music. In this contribution, I will first critically review available evidence on mammals’ capacities for vocal production learning and rhythm. I will then present: (1) longitudinal data on vocal development in seal pups, suggesting how acoustic features in seal vocalizations change with age and sex, while factoring out maturational influences due to body growth and vocal tract characteristics, (2) a case study of spontaneous vocal imitation, and a systematic experiment of noise-induced frequency shit, suggesting seal pups can modulate their fundamental frequency and formants, (3) experimental data from two groups of seals exposed to conspecific repertoires of different sizes, suggesting that limited auditory input induces less variability in an individual repertoire, (4) daily tracking of acoustic temporal structure, suggesting that pup calls become more rhythmically structured over ontogeny, (5) preliminary evidence on pinnipeds’ abilities for interactive vocal timing, obtained from group recordings, playback experiments, and computational modelling, suggesting some limited abilities for ‘turn-taking’ and ‘antisynchrony’ in pups. Taken together, this on-going research suggests that pinnipeds’ abilities to produce sounds, and to time them precisely, are more developed than previously surmised. It also supports a link between rhythmic capacities and vocal plasticity. Seals, especially in their puppyhood, can be good model species to better understand the evolution of the human speech and rhythm

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