Language is illustrated as the passing of thoughts and ideas through intelligible sounds. Although its evolutionary origins were previously unknown, a new study suggests it started at least 30 to 40 million years ago - during the time of the common ancestor of men, monkeys, and apes.
Humanity's capacity for language is based on understanding combinations and patterns of words, as well as the relationship between them. It has allowed humankind to flourish through the development and communication of ideas, culture, and technology in a more complex way not found in other species. Understanding how, why, and when it developed into its current form helps better answer what separates humans from other species.
The research paper was published in the journal Science Advances on Wednesday, October 21, by an international group of researchers led by Simon Townsend from the University of Warwick in the UK.
Adjacent and Non-Adjacent Dependency
One of the key cognitive abilities that serves as a foundation for language is the ability to take and process relationships between the words in a sentence. In language, words next to one another create what is called an "adjacent dependency," while those apart from each other is a "non-adjacent dependency."
Dr. Stuart Watson, author of the study from the University of Zurich, explains that while animals "do not produce non-adjacent dependencies in their own natural communication systems," researchers wanted to inquire whether they can still understand these setups.
To do this, researchers devised an experimental approach for the study. Researchers created "artificial grammars" : a series of meaningless tones instead of words used to observe the subjects' ability to process the relationship between these sounds. They used a combination of two or three elements taken from six different categories of sound types. To see whether the nonhuman subjects - marmosets and chimpanzees - could process the grammar, they measured the time that these animals spent looking toward the speaker. They included human subjects in the study, using only non-adjacent dependency-based grammar, as a control. Human participants were meant to ensure that the grammars made in the study was readily learnable for a linguistically capable species.
Back to a Common Ancestor
Through this setup, researchers were able to compare the ability of three different primate species to recognize non-adjacent dependencies despite not sharing a common language. Nonhuman subjects were able to detect when the established grammar was not followed, suggesting that these animals were able to understand the structural relationship between the tones.
Researchers discovered that all three species were able to process the relationship between the sounds, in both adjacent and non-adjacent dependencies. It suggests that non-adjacent dependency processing is widespread among the primate family. Through this, researchers were able to identify that this crucial cognitive facilitator of language might actually be an ancestral trait that evolved at least 40 million years before modern language as we know it.
"This indicates that this critical feature of language already existed in our ancient primate ancestors, predating the evolution of language itself by at least 30-40 million years," Professor Townsend said.
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