We know that songbirds have a sense of rhythm very similar to ours, but it is a trait rarely found in non-human mammals. Now, a team of scientists publishes a paper in the journal Current Biology in which they set out to explore musical abilities in primates. According to the researchers, finding common musical traits between species can shed light on the biology and evolution of rhythm and music.
” There has long been an interest in understanding how human musicality evolved, but this is not limited to humans, ” says Andrea Ravignani, from the Max Planck Institute for Psycholinguistics (MPI), and co-author of the study. species allows us to build an ‘evolutionary tree’ of musical traits and understand how rhythmic abilities originated and evolved in humans. “
To find out if nonhuman mammals have a sense of rhythm, the team decided to study one of the few “singing” primates, the critically endangered lemur Indri indri. The researchers wanted to know if the songs of the indri have a categorical rhythm, a “rhythmic universal” found in all human musical cultures.
Rhythm is categorical when the intervals between sounds are exactly the same length (1: 1 beat) or doubled (1: 2 beat). This type of rhythm makes a song easily recognizable, even when sung at different speeds.
For twelve years, the Turin researchers visited the Madagascar rainforest to collaborate with a local primate study group. The researchers recorded the songs of twenty groups of indri (39 animals) that lived in their natural habitat. Members of an indri family group often sing together, in harmonized duets and choruses.
The team found that indris songs had the classical rhythmic categories (both 1: 1 and 1: 2), as well as the typical “ritardando” or slowdown found in various musical traditions. The male and female songs had a different tempo, but showed the same rhythm.
Universal rhythm in a non-human mammal
According to the first author, Chiara de Gregorio, and her colleagues, this is the first evidence of a “universal rhythm” in a non-human mammal. But why would another primate produce categorical “music-like” rhythms? The ability may have evolved independently among the “singing” species, as the last common ancestor between humans and the Indri lived 77.5 million years ago. Rhythm can facilitate song production and processing, or even learning, the authors note.
“Categorical rhythms are just one of six universals that have been identified so far,” Ravignani explains. We would like to look for evidence of others, such as an underlying “repetitive” rhythm and a hierarchical organization of rhythms, both in the indri and in other species”.
The authors encourage other researchers to collect data on the indri and other endangered species, “before it is too late to witness their impressive singing displays.”
