Gorillas and chimpanzees possess a rudimentary speech centre within their brains that until now was thought to be unique to humans, scientists have found.
Brain scans of the apes – man's closest living relatives – have revealed a small, lopsided structure buried in the front part of the head which in humans is critical for language.
The structure, Brodmann's area 44, is part of the language centre known as Broca's area, and the scans reveal that it is larger and more developed in the left half of the ape's brain than in the right hemisphere – just as it is in humans.
Claudio Cantalupo and William Hopkins, who conducted the study at the Yerkes Primate Research Centre at Emory University in Atlanta, Georgia, were surprised such a critical feature within the ape's brain had gone unnoticed.
Unlike humans, apes do not have language, and communicate by grunts and hand movements. The scientists believe their brains show that the evolution of language is rooted in a common ape-human ancestor who lived more than five million years ago.
Mr Cantalupo and Mr Hopkins say in the journal Nature: "The part possession by great apes of a homologue of Broca's area is puzzling, particularly considering the discrepancy between sophisticated human speech and the primitive vocalisations of great apes."
Chimpanzees and gorillas nevertheless share one thing in common with human communication – they tend to use their right hands when grunting, which are controlled by the left-side of the brain.
"Our findings suggest that the neuro-anatomical substrates for left-hemisphere dominance in speech production were evident at least five million years ago and are not unique to hominid evolution," the scientists say. "Whatever the function of area 44 in great apes, our finding that these species show a human-like asymmetry ... indicates that the origin of asymmetry in language-related areas of the human brain should be interpreted in evolutionary terms rather than being confined to the human species."
The latest study follows work published in 1999 showing that wild chimpanzees have a relatively sophisticated culture in which they are able to pass on ideas and inventions to their offspring through teaching and learning.
Other studies at Georgia University's Language Research Centre have indicated that some chimpanzees can understand simple English sentences. Panbanisha, a hand-reared female pygmy chimpanzee, can communicate in basic phrases using a keyboard and a computer screen displaying symbols that she can press to produce a rudimentary response to a human voice.Reuse content