London: Scientists have discovered that lar gibbons use the same vocal techniques as human soprano singers to make their calls.
Researchers in Japan found that the apes also known as white-handed gibbons were able to control the natural frequencies of their "vocal tracts", a control exemplified by sopranos, and thought to be unique to humans.
The researchers analysed the calls` frequencies when the apes made calls while in an atmosphere rich in helium, BBC News reported.
The "vocal tract" - the upper oesophagus and trachea and the mouth, are well known in humans to shape sung notes and subtle vowel sounds.
In humans the vocal tract acts as a filter on the sound from the source, and the "source-filter theory" held that the separate, fine control of the vocal tract to be the product of a long evolution in the development of the subtleties of speech.
Soprano singers reach their piercing high notes by precisely controlling the shape of their vocal tract to match its natural, resonant frequency with multiples of the one being produced by their vocal folds.
Takeshi Nishimura of Kyoto University`s Primate Research Institute and colleagues tested whether lar gibbons have this same separate control - by using helium.
Presence of helium raises the pitch of the voice. It increases the natural resonant frequency in the vocal tract because the speed of sound in helium is very different from that in air.
The team recorded calls in helium and examined separately the sounds of gibbons` "pure-tone" vocalisations from the vocal folds as well as how they were modified in the vocal tract.
The study found that the gibbons modified their vocal tracts to match multiples of the vocal folds` frequencies - just like soprano singers.
"The findings upended a long history of research suggesting the control humans enjoy is the product of a long line of physiological and anatomical changes under the influence of evolution," Nishimura told BBC News.
The study was published in the American Journal of Physical Anthropology.