Although their respective lines diverged millions of years ago, bonobos and humans share 98.7% of their genome (like chimpanzees). Bonobos – which are threatened, with less than 20,000 remaining in the protected forests of the Democratic Republic of Congo – are known for their Remarkable ability to communicateEven with humans. Now research published in Science shows that they combine their vocalizations in a way that reflects how humans bring together words to form sentences, allowing them to communicate more complex messages. This capacity was once considered unique to humans.
All human languages adhere to a principle that linguists call compositionality. Approached in the 19th century by the German mathematician and philosopher Gottlob Frege, its simplest version resembles a mathematical formula: the meaning of a combination is the sum of the meanings of its parts. To explain the compositionality, the authors of the study provide a very simple example: the word “biology”, which is composed of two equally significant, organic (life) and logy (science).
Francisco J. Salguero, professor of general linguistics at the University of Seville in Spain, gives a more complete explanation: “What (this principle) says is that the meaning of a complex linguistic expression is a function of the meanings of the simple expressions that compose it and the rules used to combine these simple expressions to build creation.” This principle is adhered to all the human languages that have been studied.
“We wanted to see if bonobos also have this capacity,” explains Mélissa Berthet, principal author of the Science Paper, who studies animal communication in the Department of Evolutionary Anthropology at the University of Zurich in Switzerland.
To do this, the researchers had to understand first of all the meaning of the individual vocalizations of Bonobos. Berthet spent months with three groups in the Kokolopori Bonobo reserve, one of the last sanctuaries in these primates. “There, I followed the bonobos for 12 to 15 hours a day, observing their behavior and their vocalizations,” explains the primatologist. The reserve has three bonobos communities that are used for humans, which means that scientists can study them without interfering with their behavior.
“By following them, I used a microphone to record their vocalizations and systematically document the context in which each vocalization occurred,” explains Berthet. For everyone, she has consulted a list of more than 300 parameters to in depth the context in depth. “For example, I noted if there was a nearby group nearby, if the food was present, if the caller ate, rested or grooming, and what happened immediately after vocalization …”
By analyzing the correlations between the exit and the context of a call, she was able to identify the models. “If a particular vocalization has always been followed by the whole group group, this probably indicates that this call means” travel, “she explains. Using this approach, they were able to discover the meaning of several thousand vocalizations. Now the researchers had to determine whether the bonobos combined the vocalizations and if the combinations had their own meaning.
“More specifically, we have tested several compositionality criteria, examining whether the combination of two vocalizations produced one with a sense that could be understood from the meanings of individual calls,” explains the primatologist.
In previous work, the researchers had identified up to 11 types of individual vocalizations (grunts, low or high hulls, something that looks like a whistle, cries, etc.). In this study, they found and analyzed 38 combinations of two of these individual calls. (They also recorded more complex elements with three, four or more elements, which they will describe in future research.) After analyzing the combinations, scientists have verified that they have respected the simple version of the principle of compositionality.
But there is a more complex dimension to this principle. In the simple version, there is a sum of meanings, as in the case of the word biology. But there is also a “non -trivial compositionality” where, as Salguera explains, the linguistic professor: “One of the elements modifies the other, he finishes the other”.
It offers an example which is linked to another dimension of language: discreet infinity, where a finished set of units (morphemes or words) can generate an infinite number of combinations. “Once I have an expression like” I want water “, I can continue to build:” I want cold water “, I want cold water in a glass”, “I want cold water in a transparent glass”, I want cold water in a clear and clear glass … “” Bonobos, too, would seem to meet this criterion.
“We have excluded rare calls and combinations, so we carried out our study with seven types of calls and 19 combinations. Among them, four was compositional, a trivial and three non-trivial,” writes Berthet in an email.
This may seem a small number (although combinations of more than two vocalizations have to be studied), but it is the first time that a species other than humans has fully corresponded to the principle of compositionality. For example, the combination of a howling, which, depending on the context, points out an appeal to union, associated with an acute hululle, which generally means “paying attention”, results in a call to coordinate and move. Another example is the combination of whistles and kicks, which frequently occur in contexts of social intimacy, as During copulation.
For Professor Salguero, who was not involved in the study, “if this is really present in Bonobos, even at this very basic level of two significant signals, where one depends on the other, it would explain how it is possible that after a long evolutionary period leading to our species, the signs systems have developed this characteristic and more and more complex.”
Professor Simon W. Townsend, an animal communication expert from the University of Zurich, is a main author of the Science study. Regarding his implications beyond Bonobos, he says: “The fact that we find proofs of compositionality in humans, the chimpanzees and now Bonobos suggests that our last common ancestor, which lived about seven million years ago, also had basic composition skills, and therefore this central characteristic of language began to evolve long before the language is emerged.”
In just two months, the most prestigious scientific journals have published studies on whales following the essential laws of human languageand the way the brain processes of the budgetgars during vocalization are Surprisingly similar to those of man.
Ivan G. Torre, a researcher who has trained in animal communication systems and is now working for Oracle development communication systems for machines, recalls that at the end of the 19th and early 20th centuries, when modern linguistic theories were born, they were shaped by “an anthropocentric bias, a reserving language exclusively for humans”.
But there are growing data that contradicts this point of view. For Torre, the key lies in the need for communication, whatever the form or the species. He remembers a study he co-written, published in 2020, which focused on linguistic laws. The study revealed that in the interactions between plants and insects, the system obeyed the law of Zipf, which postulates that the most common elements (words in the case of human communication) tend to be shorter than the least common. In this case, they observed that the most common molecular chains in vegetable-animal interactions are also those formed by fewer atoms.
Ramón Ferrer I Cancho, director of the quantitative, mathematical and computer linguistics laboratory at Polytechnique University in Catalonia, compares the evolution of language to the history of the use of tools, which was once considered unique.
“Later, we learned that the chimpanzees used tools, that the dolphins chased worms under the sand with a stick … We now know the same thing about language, that it is not exclusive to humans,” explains Ferrer I Cancho, one of the main experts in human linguistics and animal communication.
Regarding the question of compositionality, he remembers a classic study in ethology published at the beginning of the century: calls from monkeys with white nose. These monkeys produce two separate alert calls: pyows warn of a leopard, and hacks Report the danger of the sky in the form of an eagle. “Researchers have found that monkeys also produce a third call, pyow-hackAnd observed that he triggers the movement of the group, ”he recalls.
The best is yet to come. Barthet has recorded more than 3,600 vocalizations over 400 hours of observation, many of which consist of more than two vocalizations. We will have to wait and see what the bonobos communicate in their combinations of three, four, five or more sounds which, so far, have seemed to be simple howls.
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