The Origins of Human Rhythm

ongoing

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, I zoom in on key rhythmic properties: isochrony, an even occurrence of events in time, and meter, a relative accentuation of events. Second, I compare hypotheses on rhythm origins, selecting the most relevant ones to music and speech and testing them against each other. Third, I target rhythm precursors in other species as predicted by these alternative hypotheses. I test four hypotheses, which propose that 1) gait or 2) breathing control, and the ability to 3) learn new sounds or 4) sing in a chorus are evolutionary precursors to human rhythm. I will use different measures including behavior, electrophysiology, gait tracking, breathing, and computational modeling to test whether the four features above predict rhythmic capacities. Comparative animal work is needed to test whether similar evolutionary pressures lead to similar rhythmic traits. I will collect data from humans and four more species. I will test seals, displaying vocal learning, and porpoises; both mammals have developed breathing control. I will also test siamangs, displaying rhythmic locomotion, and indris; both primates naturally sing in choruses, a rare trait in non-human mammals. Finding rhythm in other species will provide a test bench to reconstruct the origins of human rhythm. Resting on my background in bioacoustics and mathematics, the project expands in new challenging directions, such as neurophysiology of marine mammals, automated gait analyses, and biomusicology. In brief, I will show which species have rhythm, and why humans evolved to be such chatty, rhythmic creatures.