Helium-huffing gibbons sing like human sopranos

Humans were believed to have evolved our unique speaking ability through an evolutionary change in our anatomy, but an analysis of how gibbons sing under the effects of helium gas suggests otherwise. The study by Japanese scientists demonstrates that gibbons share the same vocal structure as humans, indicating that humans have simply learned to use our voices in a more complex way.

In their songs, gibbons use the same difficult vocal technique that soprano singers learn which allows them to put more power behind higher notes than lower ones, the researchers found. Dr Takeshi Nishimura, who led the study, said: "This is the first evidence that gibbons always sing using soprano techniques, a difficult vocalization ability for humans which is only mastered by professional opera singers.

"This gives us a new appreciation of the evolution of speech in gibbons while revealing that the physiological foundation in human speech is not so unique." Gibbons use their songs to communicate with neighbors and potential mates across up to two miles of jungle, producing a loud melody which is acoustically different to other primates. Researchers from Kyoto University recorded 20 calls made by gibbons in a zoo, and compared them with 37 calls made when the animals had breathed in helium.

The gas makes voices appear high-pitched and squeaky by altering the way our vocal tract processes the sounds we produce. In normal air the lowest frequencies of a gibbon's song are the loudest, but under the effect of helium the tuning of their vocal cords and resonance of the vocal tract changed to amplify higher frequencies. The results showed that gibbons are capable of consciously manipulating their vocal chords to make their signature calls. This suggests gibbons produce sounds in the larynx but use a filter to manipulate them, in the same way humans craft basic sounds into speech.

This is what a gibbon normally sounds like. And this is the sound of a gibbon after huffing helium. (Both links go to mp3s).