Orangutans and Humans Share Similar Speech Origins

Author: University of Warwick
Published: 21 Dec 2022
Peer Reviewed Publication: Yes

Contents: Synopsis - Definition - Introduction - Main - Related Publications

Synopsis: Research finds orangutans communicate using a complex repertoire of consonant-like calls, more so than African apes, which provides clues about how consonants became a part of the human language.

Topic Definition: Orangutan

The name orangutan means "man of the forest" in Malay. Known for their distinctive red fur, orangutans are the largest arboreal mammal, spending most of their time in trees. Long, powerful arms and grasping hands and feet allow them to move through the branches. These great apes share 96.4% of human genes and are highly intelligent creatures.

Introduction

Arboreal Origin of Consonants, and Thus, Ultimately, Speech

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).

Main Content

This contrasts with the expectation that, while closely related to humans, African apes should have call repertoires more like our speech. Arboreal versus terrestrial lifestyles has 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 ground-dwelling apes. The study suggests that our evolutionary ancestors 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. In contrast, voiceless sounds take the form of consonants.

Non-human primates have been studied for decades to find 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 how voice-less, consonant-like sounds became a fundamental component of every language spoken around the globe."

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.

Unlike other primates, but similar to spoken human language, great ape call repertoires consist of both consonant-like and vowel-like calls. However, there are inconsistencies within great apes' use of consonant sounds in nature.

"Wild gorillas, chimpanzees, and bonobos don't use a huge variety of consonant-like calls," he explains.

"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. Some chimpanzee populations produce one or two consonant-like calls associated with a single behavior, for example, while grooming. Still, these same grooming calls are uncommon in other chimpanzee populations."

"Wild orangutans, however, use consonant-like calls universally and consistently across different populations and for multiple behaviors, much like humans do with speech. Their vocal repertoire is a rich display of smacking, clicks, kiss-sounds, splutters, and raspberries."

Professor Lameira has observed orangutans in their natural habitat throughout the last 18 years and says their arboreal lifestyle and feeding habits could help explain their consonant-like calls' complexity and sophistication.

"All apes are accomplished extractive foragers. They have developed complex mechanisms to access protected or hidden foods like nuts or plant piths, which often require meticulous use of hands or tools. Apes such as gorillas and chimpanzees need the stability of the ground to handle these foods and use tools successfully. However, orangutans are largely tree-dwelling and access their food up in the canopy, where at least one of their limbs is constantly used to provide stability among the trees."

"It is because of this limitation that orangutans have developed greater control over their lips, tongue, and jaw and can use their mouths as a fifth hand to hold food and maneuver tools. Orangutans are known for peeling an orange with just their lips, so their fine oral neuro-motoric control is far superior to that of African apes, and it has evolved to be an integral part of their biology," states Dr. Lameira.

The research suggests that living in trees could have been a preadaptation for the emergence of consonants, and by extension, for speech evolution in our human ancestors.

The paper, Arboreal origin of consonants, and thus, ultimately, speech, has been published in Trends in Cognitive Sciences.

Attribution/Source(s): This peer reviewed publication was selected for publishing by the editors of Disabled World (DW) due to its relevance to the disability community. Originally authored by University of Warwick and published on 21 Dec 2022, this content may have been edited for style, clarity, or brevity.