Humans are particularly rhythmic animals. Why did the human sense of rhythm develop? Many hypotheses try to explain the origins of our acoustic rhythm capacities, but few are empirically tested, compared, and comparatively investigated. This project searches for the evolutionary roots of human rhythmicity, breaking new ground through three concerted approaches. First, it zooms in on core, measurable rhythmic properties, such as isochrony. Second, it compares hypotheses on the origin of human rhythm, selecting the most relevant ones to music and speech and testing them against each other. Third, it targets rhythm precursors in other species as predicted by these alternative hypotheses. The four hypotheses, tested against each other, propose that 1) gait or 2) breathing control, and the ability to 3) learn new sounds or 4) sing as part of a coordinated chorus are evolutionary precursors to rhythm, in human evolution and potentially in other species. We analyze behavioral, electrophysiological and physiological measures, to test whether the four features above predict rhythmic capacities, and combine them to inform computational models of the evolution of rhythmic abilities. Comparative animal work is key to test whether similar evolutionary pressures lead to similar rhythmic traits. We aim to collect data from humans and other key mammalian species. These species, chosen among primates and aquatic mammals, exhibit—each to varying degrees—the previously mentioned traits hypothesized to be precursors of rhythm: capacity to learn new sounds, developed breathing control, rhythmic locomotion, and propensity to sing in choruses. Finding rhythmic abilities and their potential precursors across species will provide a test bench to reconstruct the origins of human rhythm. The project moves the state of the art on rhythm processing abilities in new challenging directions. By connecting fields from the social sciences (experimental psychology and cognitive neuroscience), humanities (speech sciences, music theory and bio-musicology), and the “hard sciences” (bioacoustics, primatology and marine biology), we aim at showing which species have rhythm, and why humans evolved to be such chatty, rhythmic creatures.
