Songbirds have a good sense of rhythm, but this is a rare feature in non-human mammals. An international team of researchers, led by Marco Gamba, a senior researcher at the University of Turin, and Andrea Ravignani of MPI, set out to search for the musical abilities of primates. Ravignani said: "There has been a long-term interest in understanding how human musicality has evolved, but musicality is not limited to humans. Finding musical traits in other 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 non-human mammals have a sense of rhythm, the team decided to study one of the few "singing" primates, the critically endangered great lemur (scientific name Indri indri). The researchers wondered if the "songs" of the great lemur had classified rhythms, a "universality of rhythms" found in human musical culture. Rhythms are classified when the interval between sounds has exactly the same duration (1:1 rhythm) or double the duration (1:2 rhythm). This type of rhythm makes a song easily recognizable, even if it is sung at a different speed. Will the song of the Big Lemur show this "unique human" rhythm?
Over the course of twelve years, researchers from Turin visited the rainforest of Madagascar to collaborate with a local primate research team. Investigators recorded "songs" from 20 large groups of lemurs (39 animals) living in their natural habitat. Members of the Great Lemur family often sing together in the form of harmonious "duets and choruses". The team found that the "songs" of the Great Lemur had classic rhythm categories (including 1:1 and 1:2), as well as typical "ritardando" or slowing down found in some musical traditions. The "songs" of male and female lemurs have different rhythms, but show the same rhythms.
According to study first author Chiara de Gregorio and her colleagues, this is the first evidence of "rhythmic universality" in non-human mammals. But why would another primate produce a classified "music-like" rhythm? This ability may have evolved independently in the "singing" species, as the last common ancestor between humans and lemurs lived 77.5 million years ago. Rhythm may make it easier to produce and process songs, or even learn them.
"Classified rhythms are just one of the six universal phenomena that have been identified so far," Ravignani explains. "We wanted to look for other evidence, including potential 'repeating' beats and hierarchical tissues of beats – Indians and other species." The authors encourage other researchers to collect data on large lemurs and other endangered species "lemurs before it's too late to witness their breathtaking singing performances."