A window into the origin of human language

For decades, the ability to combine words to create new meanings, a characteristic of human language called compositionality in linguistics, has been considered exclusive to humans. For example, the word biology It is formed by morphemes bio-, which means life, and -lodge, which means study or science. Biology is, therefore, the study or science of life. The other, as for example when we say "good soccer player" or "attentive teacher."

In any case, since the first scientific studies in linguistics began in the 19th century, these characteristics have traditionally been considered exclusive to human language. However, several recent studies have shown that this is not entirely the case. Some primates, such as chimpanzees, and even toothed whales, such as orcas and dolphins, also use a certain composition of sounds to communicate with each other.

The most complete work that puts an end to this controversyhas just published the magazine Science. Primatologist Mélissa Berthet and her collaborators, from various Swiss, German, English and American universities and research centers, have shown that bonobos use a language with compound sounds that they structure both trivially – when the meaning of the combination of sounds is the sum of each sound – and also the sum of each sound – as well as the sum of each sound.

Bonobos, which until a few decades ago were considered to be part of the same species as chimpanzees, are, along with these primates, the most similar to the human species, both morphologically and from a cerebral and genetic perspective. It's no wonder we share 98.7% of our genome. Evolutionarily, our species began to diverge about seven million years ago, specializing and adapting to different lifestyles. They are a threatened species due to the loss of their natural habitat due to human activity. It is estimated that fewer than 20,000 remain, living in the wild in protected areas of the Democratic Republic of the Congo. This similarity to our species makes them a window into the study of our past.

The importance of context

In this study, the researchers documented more than 3,600 vocalizations of wild bonobos in the Kokolopori Community Reserve. To determine whether some of their vocalizations are composite and to understand their meaning as much as possible, they spent several months following three specific groups of bonobos. They recorded more than 700 sounds or combinations of sounds, and for each group, they documented around 300 parameters to comprehensively describe the context in which they occurred, such as whether another group of bonobos was nearby, whether they were resting or sheltering, whether there was food in the area or if they were eating in the area, and what happened immediately after the vocalization.

By analyzing the context in which these vocalizations were produced, which included grunts, squeals, high-pitched howls, low-pitched howls, whispers, and hisses, and very diverse combinations of these basic elements, such as grunts + squeal, or whisper + squeal + squeal + they identified 38 different combinations, of which 19 showed clear evidence of compositionality, and which included both trivial and non-trivial compositionality. That is, some combinations had meanings that could be directly deduced from their parts, while others showed more complex modifications, in which one sound altered or completed the meaning of another.

Exclusively human?

This discovery suggests that the ability to combine sounds to create new meanings may have been present in the common ancestor of humans and bonobos, who lived between seven and thirteen million years ago. This fact challenges the idea that complex language is a uniquely human innovation and opens the door to a deeper understanding of how communication has evolved in primates.

However, there is a key difference between the bonobo and human communication systems. In other primates, the meanings conveyed by their vocalizations are always literal. Cognitive linguistic It shows that, on average, 13% of the words we use in conversation are related to some metaphor. The symbolic capacity of the human brain allows us to exponentially increase the communicative power of our language by using the composition of sounds symbolically and metaphorically.