Another aspect thought to be unique to humans has been spotted in baboons.

Baboons can make five different vowel-like sounds when they're grunting, barking, wahoo-ing, calling, and yakking, according to an international team of researchers.

Scientists thought that the uniquely low location of the human voice box was what let us make vowel sounds, and eventually speak, but analysis of over 1,300 sound clips from baboons has found that they make five sounds that are similar human-made vowels. 

Many scientists believe that language originated emerged recently, within the last 70,000 –100,000 years, so little research on links between the vocalisation of nonhuman primates and human speech has been undertaken.

To investigate, researcher Louis-Jean Boë from France’s Grenoble Alpes University and colleagues analysed 1335 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.

They found that people form each vowel sound with a precise control of tongue position in the vocal tract, and that baboon tongues have the same muscles as human tongues.

This suggests that these monkeys likewise use tongue movements to form each of the vowel-like sounds.

Taken together, these findings suggest that spoken language in people may have evolved from abilities that were already possessed by our last common ancestor with baboons, about 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,” says co-author Joel Fagot.

The full study is accessible here.