Humans Still Understand Chimpanzee and Bonobo Gestures

Topic: Deaf Communication
Author: PLOS
Published: 2023/01/24 - Updated: 2023/01/25 - Peer-Reviewed: Yes
Contents: Summary - Definition - Introduction - Main - Related

Synopsis: The discovery of gestures used by great apes provides evidence of intentional communication outside human language; over 80 such signals have now been identified. These gestures are shared across non-human apes, including distantly related apes such as chimpanzees and orangutans. The results suggest that although we no longer use these gestures, we may have retained an understanding of this ancestral communication system.

Defining Great Apes

Great Apes

The first apes evolved about 25 million years ago and were a very diverse group by 20 million years ago. Within the last 10 million years, many ape species became extinct as the earth's climate cooled and dried, and their forested environments changed to woodland and grassland. There are now only about 20 living species of apes, and they are divided into two major groups. These are the:

Lesser Apes, containing the gibbons
Great Apes, containing the orangutans, gorillas, chimpanzees, and humans

The Hominidae, whose members are known as the great apes or hominids, are a taxonomic family of primates that includes eight extant species in four genera: Pongo (the Bornean, Sumatran, and Tapanuli orangutan); Gorilla (the eastern and western gorilla); Pan (the chimpanzee and the bonobo); and Homo, of which only modern humans (Homo sapiens) remain. The 8 Great Apes Are:

Bonobo (also known as pygmy chimpanzee), Pan paniscus
Bornean orangutan, Pongo pygmaeus
Chimpanzee, Pan troglodytes
Eastern gorilla (includes two subspecies: mountain gorilla and Grauer's/eastern lowland gorilla), Gorilla beringei
Human, Homo sapiens. Humans are primates and are classified along with all other apes in a primate sub-group known as the hominoids (Superfamily Hominoidea).
Sumatran orangutan, Pongo abelii
Tapanuli orangutan, Pongo tapanuliensis
Western gorilla, Gorilla gorilla

Introduction

Towards a Great Ape Dictionary: Inexperienced Humans Understand Common Nonhuman Ape Gestures - PLoS Biology.

Humans retain an understanding of gestures made by other great apes, even though we no longer use them ourselves, according to a study by Kirsty E. Graham and Catherine Hobaiter at the University of St Andrews, Scotland, publishing January 24th in the open access journal PLOS Biology.

Main Digest

The discovery of gestures used by great apes provided the first evidence of intentional communication outside human language, and over 80 such signals have now been identified.

Many of these gestures are shared across non-human apes, including distantly related apes such as chimpanzees and orangutans. However, despite humans being more closely related to chimpanzees and bonobos, these ape gestures are no longer thought to be present in human communication.

Continued below image.

Chimpanzees use many different gestures to communicate, like this reach they usually use to ask for food. Participants selected the correct meaning for the reach gesture and were overall able to understand ape gestures - Image Credit: Catherine Hobaiter.

Continued...

Researchers tested people's understanding of the ten most common gestures used by chimpanzees (Pan troglodytes) and bonobos (Pan paniscus) using an online game.

Over 5,500 participants were asked to view 20 short videos of ape gestures and select the meaning of the gesture from four possible answers. They found that participants performed significantly better than expected by chance, correctly interpreting the meaning of chimpanzee and bonobo gestures over 50% of the time.

Providing participants with contextual information about what the apes in the video were doing only marginally increased their success rate in interpreting the meaning of the gesture.

Video playback experiments have traditionally been used to test language comprehension in non-human primates, but this study reversed the paradigm to assess humans' abilities to understand the gestures of their closest living relatives for the first time.

The results suggest that although we no longer use these gestures, we may have retained an understanding of this ancestral communication system. The authors say that it remains unclear whether our ability to understand specific great ape gestures is inherited or whether humans and other great apes share an ability to interpret meaningful signals because of their general intelligence, physical resemblance, and similar social goals.

Continued below image.

The online experiment could be completed on a laptop or tablet. A little cartoon showed participants what gesture they were looking for in the video, and half of the participants were told what the apes were doing - Image Credit: Kirsty E. Graham.

Continued...

Graham adds:

"All great apes use gestures, but humans are so gestural - using gestures while we speak and sign, learning new gestures, pantomiming, etc. - that it's really hard to pick out shared great ape gestures just by observing people. By showing participants videos of common great ape gestures instead, we found that people can understand these gestures, suggesting that they may form part of an evolutionarily ancient, shared gesture vocabulary across all great ape species, including us."

Attribution/Source(s):

This peer reviewed publication was selected for publishing by the editors of Disabled World due to its significant relevance to the disability community. Originally authored by PLOS, and published on 2023/01/24 (Edit Update: 2023/01/25), the content may have been edited for style, clarity, or brevity. For further details or clarifications, PLOS can be contacted at plos.org. NOTE: Disabled World does not provide any warranties or endorsements related to this article.

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