Male and female gibbons sing duets in time with each other

Gibbons emit synchronous, regularly spaced sounds. This is a musical quality previously found only in lemurs and humans.

To James Dineen

Male and female gibbons sing duets with synchronized, regularly spaced notes. These are rhythmic qualities similar to those found in human singing, which may suggest an evolutionary basis for the origin of music.

Andrea Lavignani of the Max Planck Institute for Psycholinguistics in the Netherlands, referring to the ability to sing regularly repeated notes, said, “I am convinced that the gibbons’ isochronous abilities are superior to mine. I will.” This ability is indris (Indri Indri), a type of lemur found in Madagascar and the only other primate with a call exhibiting a distinctive rhythm associated with that found in human music.

Male and female gibbons regularly sing duets to define territories and form social bonds. Ravignani and his colleagues analyzed 215 songs recorded from 12 pairs of gibbons.Hylobates lar) two from Thailand and two from an Italian wildlife sanctuary.

After separating male and female vocalizations based on pitch, the researchers marked the starting point of every sound. They measured how often notes were repeated at regular intervals and how often male and female notes overlapped during a duet.

Regular rhythms were found in all songs of gibbons, but males sang with more regular beats in duets than when singing solo. In duets, the male and female singer’s notes overlapped 16–18% of the time with her, and the rate of synchrony was higher than chance.

Researchers also found a connection between the two rhythmic qualities. If the female’s call overlaps with the male’s, the female will sing less regularly. This shows that gibbons’ rhythms differ according to their social background, he says, Ravignani.

Henkjan Honing of the University of Amsterdam said the findings suggest that evolution may have opted for primate-like rhythmic abilities as a way to coordinate vocal presentations..

However, it is unclear whether the last common ancestor of primates possessed such an ability, or whether it emerged later through convergent evolution “piggybacking on the same kind of cognitive architecture,” says Simon Townsend says.

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