Bonobos communicate a lot like humans
- Bonobos have been found to communicate in complex ways similar to humans, using combinations of calls that convey meaningful information.
- A new study used novel methods from linguistics to demonstrate that bonobo vocal communication relies on compositionality, a key feature of human language.
- The researchers created a “bonobo dictionary” by quantifying the meaning of individual bonobo calls and then investigating call combinations to understand how their meanings relate to each other.
- The study found numerous call combinations whose meaning is related to the meaning of their single parts, suggesting that compositionality may be an evolutionary trait shared with humans.
- The findings suggest that our ancestors likely used compositionality in their vocal communication at least 7 million years ago, and that bonobo vocal communication shares more similarities with human language than previously thought.
Bonobos—our closest living relatives—create complex and meaningful combinations of calls resembling the word combinations of humans, researchers report.
The new study investigated the vocal behavior of wild bonobos in the Kokolopori Community Reserve in the Democratic Republic of Congo.
Researchers at the University of Zürich and Harvard University used novel methods borrowed from linguistics to demonstrate for the first time that, similarly to human language, bonobo vocal communication relies extensively on compositionality.
Compositionality is the capacity to combine meaningful words into phrases whose meaning is related to the meaning of the words and the way they are combined.
In more trivial compositionality, the meaning of the combination is the addition of its parts: for example, “blond dancer” refers to a person who is both blond and a dancer. However, in more complex, nontrivial compositionality, one part of the combination modifies the other. For example, “bad dancer” does not refer to a bad person who is also a dancer: “bad” in this case does not have an independent meaning but complements “dancer”.
In a first step, the researchers applied a method developed by linguists to quantify the meaning of human words.
“This allowed us to create a bonobo dictionary of sorts—a complete list of bonobo calls and their meaning,” says Mélissa Berthet, a postdoctoral researcher at the evolutionary anthropology department of the University of Zurich and lead researcher of the study.
“This represents an important step towards understanding the communication of other species, as it is the first time that we have determined the meaning of calls across the whole vocal repertoire of an animal.”
After determining the meaning of single bonobo vocalizations, the researchers then moved on to investigating call combinations, using another approach borrowed from linguistics.
“With our approach, we were able to quantify how the meaning of bonobo single calls and call combinations relate to each other,” says Simon Townsend, a University of Zurich professor and senior author of the study.
The researchers found numerous call combinations whose meaning was related to the meaning of their single parts, a key hallmark of compositionality. Furthermore, some of the call combinations bore a striking resemblance to the more complex nontrivial compositional structures in human language.
“This suggests that the capacity to combine call types in complex ways is not as unique to humans as we once thought,” says Berthet.
An important implication of this research is the potential light it sheds on the evolutionary roots of language’s compositional nature.
“Since humans and bonobos had a common ancestor approximately 7 to 13 million years ago, they share many traits by descent, and it appears that compositionality is likely one of them,” says Harvard Professor Martin Surbeck, coauthor of the study.
“Our study therefore suggests that our ancestors already extensively used compositionality at least 7 million years ago, if not more,” adds Townsend.
The findings also indicate that the ability to construct complex meanings from smaller vocal units existed long before human language emerged, and that bonobo vocal communication shares more similarities with human language than previously thought.
The research appears in Science.
Source: University of Zurich
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