Chimpanzees Saying “Mama” May Reveal Neural Building Blocks for Speech

Old recordings of captive chimpanzees saying the word “mama” indicate that our nearest living relatives may, after all, possess the neural foundations needed for speech.

For decades, researchers have assumed that differences in primate brains account for humans being uniquely able to form meaningful sounds. However, after examining two chimpanzees featured in a publicly available home video and a newsreel from the 1960s, phonetician and cognitive scientist Axel Ekström of KTH Royal Institute of Technology and his colleagues argue that this assumption may rest on a false premise.

Chimpanzees and the neural basis for speech

“The hypothesized missing link precluding chimpanzees from voluntary jaw-voice coupling evidently does not exist,” the researchers declare in their paper.

While searching archived public videos, Ekström’s team identified two unrelated chimpanzees (Pan troglodytes) on separate continents producing a sound resembling ‘mama’. It is claimed that the animals had been taught the word by their English-speaking carers.

“It has been argued that ‘mama’ may have been among the first words to appear in human speech,” explain the researchers.

The ‘m’ sound occurs widely in human languages and is commonly among the earliest sounds made by human infants. As a result, an ‘m-vowel-m’ sequence is comparatively straightforward for humans to form.

Evidence of chimpanzee vocal learning

Together with an earlier study in which Ekström examined an audio recording of a third chimpanzee in a 1960s television film saying the words ‘papa’ and ‘cup’, the new findings suggest that chimpanzee brains can deliberately reproduce at least certain sounds they hear.

“These results corroborate a growing body of evidence that great apes are vocal production learners,” the researchers write.

This would mean that the neurological audiovocal system shared by humans - and which has also arisen independently in songbirds - may be far more ancient than previously believed. The human and chimpanzee branches of the primate family tree last shared a common ancestor millions of years ago.

One video showed Johnny, a chimpanzee at Florida’s Suncoast Primate Sanctuary.

“Johnny called everyone Mama”, said the video account owner. He “knew that [saying] Mama would get him anything he wanted as long as it was on his diet…”

Although wild chimpanzees generally rely more on gestures than sounds when communicating with one another, they nevertheless make a variety of vocalisations. Their gesture-based language is also organised in the same way as our spoken language. Gibbons, meanwhile, are known to make more than 20 distinct sounds with separate meanings.

Reassessing historic great ape language studies

Earlier accounts of primate speech were “dismissed in the absence of rigorous analysis”, but Ekström and his team say this merely demonstrates that a lack of evidence is not evidence of absence. In their view, researchers have put too much faith in classic studies with seriously questionable ethics, which probably distorted the findings.

Animals involved in the well-known great ape language projects 50 years ago were kept in unnatural circumstances, including social isolation and neglect, frequently after being traumatically separated from their mothers. Such treatment would not have enabled these necessarily social and highly intelligent primates to demonstrate their capabilities fairly.

Efforts to avoid attributing human qualities to animal subjects have sometimes instead produced bias at the other extreme, helping to drive major underestimations of animal intelligence.

Yet, just as science advances human understanding step by step, human intelligence is also built on foundations that existed before our species.

“Great apes can produce human words,” Ekström and colleagues conclude. “The failure to demonstrate this half a century ago was the fault of the researchers, not the animals.”

The research was published in Scientific Reports.