Even if the complexity or expressions fall short of human languages, it is well known that some animal species use incredibly complicated languages of their own. Baboons, which have already shown the ability to distinguish real words from gibberish, have now been found to also use vowel-like sounds in their speech, an ability that was thought to exist only in humans.

A theory of human speech evolution used our anatomy — specifically the low-situated larynx — to explain why we, as a species, could produce distinct vowel sounds, while other primates, with their high larynxes, could not. Using this reasoning, it is believed that language evolved relatively recently, about 70,000 to 100,000 years ago. But a study published Wednesday in the journal PLOS ONE challenges that theory, and by extension, the time frame of when human speech is thought to have evolved.

Titled “Evidence of a Vocalic Proto-System in the Baboon (Papio papio) Suggests Pre-Hominin Speech Precursors,” the study by Louis-Jean Boë and colleagues from Grenoble Alpes University, France, looks at the links between speech patterns of humans and other non-human primates.

According to a press release, the researchers “analyzed 1,335 spontaneous vocalizations produced by 15 male and female Guinea baboons in different social contexts, and studied the anatomy of vocal tracts from two baboons that died of natural causes.”

Based on acoustic analysis and studying tongue anatomy, they found that baboons make five distinct sounds that have “important similarities” with vowels used in human speech. The researchers surmised that the languages spoken by humans may have evolved from capacities of vocal articulation that existed in the last common ancestors we share with baboons, which existed 25 million years ago.

“Similarities between humans and baboons suggest that the vowels of human speech probably evolved from ancient articulatory precursors that were passed on and refined all along the hominid line,” study co-author Joel Fagot said.