Study finds evolution of human speech by studying orangutan communication

A new study finds a key piece of the puzzle about how human speech and language evolved to be what it is today. This comes after researchers spent decades studying non-human primates and might have found the answer in tree-dwelling apes like orangutans, rather than ground-dwelling apes (gorillas, bonobos and chimpanzees).

Published in the Trends in Cognitive Sciences on Tuesday, the study was conducted by a researcher from the University of Warwick, United Kingdom. The study found that orangutans produce consonant-like calls more often and of a greater variety than their ground-dwelling cousins, which could also be becausehumans and orangutans share at least 97 per cent of their DNA.

While the study attributes this tothe orangutans’ arboreal lifestyle which has seemingly driven them to develop different vocal repertoires, with large and varied inventories of consonant-like calls. Therefore, the study also suggests that our ancestors were more tree-dwelling than previously thought.

In a statement, the author of the study and associate professor of psychology at the University of Warwick, Dr Adriano Lameira, said, “Existing theories of speech evolution have thus far, focused exclusively on the connection between primate laryngeal anatomy and human use of vowels.” He added, “This doesn’t explain, though, how voice-less, consonant-like sounds became a fundamental component of every language spoken around the globe.”

This is of course in reference to how all spoken languages are composed of both vowels and consonants, while the former is always produced by the larynx, a cartilaginous segment of the throat, while the latter is typically more voiceless and produced moving lips, tongue, and mandible (lower jaw).

Therefore, in order to understand the origins of speech and the root-cause of consonant sounds in humans, the researcher compared patterns of consonant-like vocal production in the three aforementioned major great ape lineages. Additionally, unlike most primates and similar to human languages the great ape communication also consisted of both consonant-like and vowel-like calls, said the study.

“Wild gorillas, chimpanzees and bonobos don’t use a huge variety of consonant-like calls…Gorillas for example, have been found to use a particular consonant-like call, but this is only prevalent in some gorilla populations and not others,” Lameria noted.

Meanwhile, some chimpanzee populations produce one or two consonant-like calls associated with a single behaviour, like grooming, he added. However, these same grooming calls are uncommon in other chimpanzee populations.

On the other hand, wild orangutans use “consonant-like calls universally and consistently across different populations and for multiple behaviours, much like humans do with speech”, said the researcher. He also describes the orangutans’ vocal repertoire as a “rich display of smacking, clicks, kiss-sounds, splutters and raspberries.”

The author also believes that orangutans’ arboreal lifestyle and their limitation of using at least one limb constantly to provide stability among the trees to them overtime developing “greater control over their lips, tongue and jaw and can use their mouths as a fifth hand to hold food and manoeuvre tools.”

He also gives an example of how arboreal-dwelling apes can peel an orange using just their lips, “so their oral neuro-motoric control is far superior to that of African apes which evolved to become an integral part of their biology”. Therefore,research suggests that living in trees could have been a preadaptation fororangutans’ consonant-like calls which eventually led tospeech evolution in our human ancestors.

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