For most humans, speech flows naturally. A child's first words are celebrated, but once we are lingual, we just open our mouths and speak. But how did we come to have smooth, spoken language?

Scientists have turned to our relatives, non-human primates, for answers. In the hunt for what makes us unique, researchers have some ideas. One distinction they have long highlighted is the position of humans' voice box. Humans have a low larynx, while other primates have a high larynx. And scientists have thought that a low larynx is required to produce a variety of distinct vowel sounds, thought to be necessary for spoken language.

But now scientists are shifting their thinking. Vowel sounds might not be such a unique characteristic of human vocalizations, as a new study of baboons finds that they, too, produce five vowel sounds in their calls.

Not only could this upend researchers' ideas of what makes human vocalization unique, it could also suggest the roots of human speech lie much further back in the primate family tree.

Vowels are produced by manipulating the vocal tract and are thought to be particularly difficult to produce for animals with vocal tracts distinct from ours, explains Thore Jon Bergman, an evolutionary biopsychologist at the University of Michigan who was not part of the baboon study. "The idea was that, based on their anatomy, primates just didn't have the ability to produce a wide range of formant positions, which are needed to make the vowel sounds – which is clearly not true."

That's not to say that a baboon can actually speak smoothly like a human and has just been holding out on us. This paper is probably suggesting that "if you somehow were able to wire a human brain up to a baboon vocal tract, you would be able to probably make yourself understood," Dr. Bergman tells the Monitor in a phone interview, though the sounds could be slurred and mushy.

Read the full article "Can baboons make human-like vowel sounds?" at The Christian Science Monitor.