Mark Kaser/University of Durham/PA

An orangutan has shown an ability to emulate human speech for the first time — a feat that gets us closer to understanding how human speech first evolved from the communications of ancestral great apes.

‘Rocky’ the ginger ape has astonished experts by producing sounds similar to words in a “conversational context”.

“This opens up the potential for us to learn more about the vocal capacities of early hominids that lived before the split between the orangutan and human lineages to see how the vocal system evolved towards full-blown speech in humans,” says lead researcher Adriano Lameria, from the University of Durham, UK.

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His team conducted a game in which the ape mimicked the pitch and tone of human sounds and made vowel-like calls.

Comparing his sounds against a large database of recordings of wild and captive orangutans showed they were markedly different.

Rocky was able to learn new sounds and control the action of his voice in the way humans do when they conduct a conversation, the scientists concluded.

“Instead of learning new sounds, it has been presumed that sounds made by great apes are driven by arousal over which they have no control,” says Lameria. “But our research proves that orangutans have the potential capacity to control the action of their voices.”

“This indicates that the voice control shown by humans could derive from an evolutionary ancestor with similar voice control capacities as those found in orangutans and in all great apes more generally,” he says.

Eight-year-old Rocky was studied at Indianapolis Zoo in the US, where he still lives, between April and May 2012.

In the “do-as-I-do” game he attempted to copy random sounds made by the experimenter which included variations in tone and pitch.

His calls were compared with sounds collected from more than 12,000 hours of observations of more than 120 orangutans from 15 wild and captive populations.

A previous study led by Lameira when he was based at the University of Amsterdam found that a female orangutan called Tilda was able to make sounds that had the same rhythm and pace as human speech.

Journal reference: Scientific Reports, DOI: 10.1038/srep30315

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