When language first emerged in humans is a popular topic of debate. At present, the most popular theory dates it to between 70,000 and 100,000 years ago, but evidence is increasingly showing its origins go back much further, with researchers now finding the capacity for language was present some 25 million years ago.
Louis-Jean Boe and colleagues were looking at baboon vocalisations to establish whether or not they have the capacity to produce vowel-like sounds that involves the control of their vocal tract. Previously, it was thought the high positioning of the larynx in their vocal tract meant baboons were incapable of doing this. Furthermore, the low position of the larynx in humans was thought to be the reason we are able to speak.
"This theory has often been used to buttress the theoretical claim of a recent date for language origin, e.g. 70,000–100,000 years ago," they wrote in the journal PLOS One. "It also diverted scientists' interests away from articulated sound in nonhuman primates as a potential homolog of human speech."
The team carried out an acoustical analysis of 1,335 different grunts, barks, wahoos, copulation calls, and yaks from male and female Guinea baboons in various social contexts. They found that baboons are able to produce five distinct vowel-like sounds.
Researchers then studied the anatomy of the baboon vocal tracts, the tongue muscle and the vocal fold lengths. "Compared with humans, baboons have a child-like vocal tract but adult-like vocal folds," they wrote. The dissection indicated the vowel-like sounds were produced by a specific motion "in a manner clearly comparable to the two articulatory-acoustic dimensions universal to human speech".
As a result, the researchers say the capacity for spoken language dates back to at least 25 million years ago – when the last common ancestor we shared with baboons lived.
The findings do not suggest baboons could ever develop some form of language. Study author Joel Fagot told IBTimes UK: "Our study shows that their spontaneous vocalisations contains sounds which are comparable to the human vowels. However, spoken languages require much more than the sole capacity to make vowels, and the ability to produce vowels is only one of the many building blocks of spoken language. Spoken languages in humans requires in particular cognitive competences that our monkeys might miss, or might have but to a much more limited extent than humans.
"The main message of our study is that the baboons at least is capable of producing five different sounds comparable to vowels, in spite of their high larynx. This suggests that this capacity has a long evolutionary history of at least 25-30 million years, and it independent of the position of the larynx."
In terms of when humans first began talking, Fagot said it is still a mystery: "The first author of our group has already that the vocal tract of Neanderthal has the potential for producing the sounds of speech, but it is unfortunately impossible to know if they use theses sounds in their daily life."