Orang-utan calls 'like human talk'
Lip-smacking calls made by orang-utans show striking similarities to human spoken languages, scientists have learned.
The discovery may highlight a possible starting point for the evolution of speech, the researchers believe.
Dr Adriano Lameira, from the non-profit Pongo Foundation, which conducts orang-utan studies, 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."
How humans developed the power of speech remains one of science's great unsolved mysteries.
The new research reported in the journal Public Library of Science ONE shows that orang-utans, and perhaps other great apes, can learn to produce new calls which have much in common with human spoken words.
Dr Lameira added: " 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 change all of this as we can now see fundamental similarities."
Co-author Professor Serge Wich, from Liverpool John Moores University, said: " This research highlights that studying orang-utan calls is very relevant to our understanding of the evolution of the production of human speech.
"Orang-utans 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."