Orangutan learns to whistle tunes and mimic human speech
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It may seem like something from the Planet of the Apes franchise, but it appears orangutans are capable of learning how to make sounds in a similar way to human speech.
Researchers studying a female orangutan called Tilda at Cologne Zoo, in Germany, discovered she has learned to whistle tunes and makes sounds comparable to human consonants.
Born in the wild in Borneo during the 1960s before she was captured at the age of two, she has spent nearly 50 years in captivity.
Scroll down for video and to hear Tilda make her unusual calls
Tilda, a female orang-utan at Cologne Zoo pictured above, has developed an unusual way of communicating with zookeepers by whistling tunes and producing a series of clicks and grunts that mimic human speech
In that time it appears she has learned that she can attract the attention of zookeepers by producing whistles and a series of rhythmical clicks.
A team of biologists who have now studied her unusual calls have found that she produces the clicks by imitating the mouth movements used in speech.
The movement of her lips and tongue are similar to those used by humans to produce the consonants 't', 'k' and 'p'. She also produces 'faux -speech' grunts that are similar to human vowel sounds.
The researchers found that to do this, Tilda rapidly opens and closes her mouth in rhythms comparable to those used to create human speech.
The rhythms she used were seven times faster than those seen in typical orangutan calls.
Although the sounds she produces are difficult to compare to human speech, the scientists claim the movements she makes require the kind of fine control over her lips and tongue that was thought to be restricted to humans among primates.
They believe the findings may help to explain how human speech first evolved.
Professor Serge Wich, a primatologist at Liverpool John Moores Univesrity who was involved in the study, said: 'This research highlights that studying orang-utan calls is very relevant to our understanding of the evolution of the production of human speech.
'Orangutans seem to have more capabilities to learn and produce calls than we assumed several years ago.
'This indicated how important studies are that examine calls in this relatively silent ape species.'
Zookeepers at Cologne Zoo believe Tilda was initially trained to perform tricks for human entertainment, which may help explain some of her unusual behaviours.
From 1975 she was housed at a Zoo in Switzerland before being transferred to Zoo Krefeld in Germany in 2007 and then a year later being moved to the Cologne Zoo where she remains.
Tilda is thought to have first learned to produce the calls by copying a human trainer at some point in the past.
In the film Rise of the Planet of the Apes (above) primates learn to speak after being exposed to a virus, but the latest study suggests apes can already learn how to mimic the mouth movements that humans use in speech
However, according to Dr Adriano Lameira, from the University of Amsterdam, who led the new research, she now produces these calls without prompting.
He said that she produces them with a specific goal in mind - clapping her hands or pointing at food in the caretakers hands as she vocalises.
In their study, which is published in the journal Public Library of Science One, the scientists analysed video and audio recordings of Tilda communicating.
They looked at the way she opens and closes her mouth and found she used rhythms similar to those used in human speech.
Dr Lameira, who also works for conservation charity the Pongo Foundation, said: 'These calls were produced by quickly opening-and-closing the lips, much alike humans do when talking.
'One of these calls presented similarities with human consonants, and the other with human vowels, the two basic building blocks of human speech.'
Clicks sounds occur as consonants in many languages around the world but the Khoisan languages in southern Africa contain the widest use of clicks.
The Juǀʼhoan language, for example, has 48 click consonants, among nearly as many non-click consonants.
Tilda, above, is thought to be around 50 years old and learned to produce the calls by copying a human trainer
The scientists analysed the sounds and mouth movements of Tilda as she produced her clicks (left hand graph) and vowel like grunts (right hand graph). The dark blue line shows the power of the sound, the light blue line shows the acoustic amplitude and the red line indicates how the distance between her lips changed
Some anthropologists believe these click languages may have been among the first forms of human speech to emerge.
Dr Lameira said: 'Speech underlines every social and community structure in human society, yet the origin of all the world's spoken languages remains a puzzle ever since the publication of Darwin's theory of natural selection.
'The major barrier for our understanding of the evolution of spoken language is the observation that great apes – our closest relatives – exhibit a very rigid use of their calls, and seem to lack the capacity to modify or learn new calls into their repertoire.
'This stands in stark contrast with human spoken languages, which are learned anew every generation, raising therefore critical questions about evolutionary continuity between our vocal repertoire and that of great apes.
'The new findings changes all of this as we can now see fundamental similarities.'
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