A team of researchers has found that macaque monkeys have the proper vocal anatomy for producing human-like speech but lack the necessary brain development. The findings will help scientists better understand the evolution of primate speech. The details are in a paper that was just published in the journal Science Advances.
Human speech is a unique ability that allows for complex communication. In the past, scientists have suggested that speech is a feature of human anatomy. Nonhuman primates, such as chimpanzees and monkeys, lack the proper anatomical features to be capable of human-like speech. Specifically, past research has focused on the vocal tract—which supposedly wouldn’t allow monkeys to speak due to differences in anatomy. This idea was based on a single study that used monkey cadavers, however, and a team of scientists set out to see if the theory still held up.
Researchers from Princeton University, the University of Vienna, and the VUB Artificial Intelligence Laboratory in Belgium collaborated to better determine whether or not nonhuman primates had the proper anatomy for true speech. The team analyzed x-ray videos of macaque monkeys vocalizing or otherwise using their mouths to study the vocal tract. This information was added to a computer model that could demonstrate the complete vocal range of macaques.
The team found that the macaque vocal tract anatomy could actually support human speech. They could make a wide range of sounds that could be used to form a complex spoken language. In fact, the team concluded that macaques could even form intelligible sentences. This means that lack of human-like speech is not due to vocal tract anatomical limitations but rather the primate brain. Macaques technically have the ability to produce speech but don’t have the proper brain development to support human-like speech.
The research team’s findings provide new insights into the evolution of human speech. Nonhuman primates have the anatomy for speech but not the brain structures. Scientists still aren’t sure what makes the human brain “special” in this regard but further research may uncover this mystery.
Fitch et al. Monkey vocal tracts are speech-ready. Science Advances (2016).