Orangutan communication sheds light on human speech origins

New research from The University of Warwick has revealed that orangutans, the most arboreal of the great apes, produce consonant-like calls more often and of greater variety than their African ground-dwelling cousins (gorillas, bonobos and chimpanzees).

This contrasts with the expectation that, whilst being closely related to humans, African apes should have call repertoires which are more like our speech. Arboreal versus terrestrial lifestyles appear to have driven great apes to develop different vocal repertoires, with large and varied inventories of consonant-like calls arising from tree-dwelling apes like orangutans, rather than the ground-dwelling apes. The study suggests that our own evolutionary ancestors might have lived a more tree-dwelling lifestyle than previously thought.

Dr Adriano Lameira, Associate Professor of Psychology at The University of Warwick, investigated the origins of human spoken language, which is universally composed of vowels that take the form of voiced sounds, whereas voiceless sounds take the form of consonants.

Non-human primates have been studied for decades in search for clues about how speech and language evolved in our species. However, the calls of non-human primates are composed primarily or exclusively of voiced vowel-like sounds. “This raises questions about where all the consonants, that compose all the world’s languages, originally come from,” says Dr Adriano Lameira.

“Existing theories of speech evolution have thus far, focused exclusively on the connection between primate laryngeal anatomy and human use of vowels.

“This doesn’t explain though, how voice-less, consonant-like sounds became a fundamental component of every language spoken around the globe.”

In order to understand the origins of human speech and the root-cause of consonant sounds in the human lineage, Dr Lameira compared patterns of consonant-like vocal production in the vocal repertoire of three major great ape lineages that survive today from a once-diverse family — orangutans, gorillas, bonobos and chimpanzees.

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