Language evolved around 30 million years ago, when primates developed the capacity to understand the structure of sentences, scientists have claimed.
Researchers believe the ability humans have to understand relationships between words in a sentence may have come from the last common ancestor of monkeys, apes and humans.
It is now thought this “critical feature” of communication existed long before language more fully took shape with the arrival of so-called anatomically modern Homo sapiens around 200,000 years ago.
The findings were made in a study that examined the language processing abilities in chimpanzees, humans and common marmosets - a Brazilian monkey.
Both apes and monkeys were found to be able to track relationships between sounds the same way as humans, which is an ability distinct from being able to talk, but one crucial to comprehending language.
Professor Simon Townsend at the University of Warwick, who led the study published in Science Advances, said: “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.”
Prof Townsend and his colleagues analysed how primates process relationships between individual tones and a string of sounds, much like words in a sentence.
They did so by looking at words which are next to one another – known as an adjacent dependency – as well as words that are distant to one another – known as a non-adjacent dependency.
The team said that being able to process relationships between words in a sentence is one of the key cognitive abilities underpinning language.
One example was the sentence: “The dog who bit the cat ran away.”
In this sentence, we understand that the dog ran away rather than the cat thanks to our ability to process the relationship between the first and second action described.
Dr Stuart Watson, from the University of Zurich, said: “Most animals do not produce non-adjacent dependencies in their own natural communication systems, but we wanted to know whether they might nevertheless be able to understand them.”
The researchers created “artificial grammars” – where sequences made up of meaningless sounds instead of words were used to examine the abilities of the test subjects to process the relationships between sounds.
They found that all three species were readily able to process the relationships between both adjacent and non-adjacent sound elements.
The study authors wrote: “These notable similarities between monkeys, apes, and humans indicate that nonadjacent dependency processing, a crucial cognitive facilitator of language, is an ancestral trait that evolved at least (around) 40 million years before language itself.”