Orangutans and human speech

A recent study, led by scientists from the University of St Andrews and Indianapolis Zoo, has found that great apes are able to control their voice in a similar way as humans do, thus unveiling insight into the evolution of human language.

The study, which was conducted in collaboration with the University of Durham, involved studying two orangutans, and how they use their voices to play a basic musical instrument. Active voicing, which consists in ‘voluntary control over vocal fold oscillation’, is deemed to be essential for speech. Traditionally, it was presumed uniquely human, however nowadays, there is a growing volume of multidisciplinary data evidencing voice control in great apes.

The team of researchers were able to successfully develop a diagnostic test for active voicing in orangutans by using a membranophone, which is a musical instrument where ‘a player’s voice flares a membrane’s vibration through oscillating air pressure’. This musical instrument was chosen for the study because it is strictly and solely activated by the player’s voice, thus controlling for any potential external effects or factors. By giving these to the orangutans, the team determined that the apes have good levels of voice control, which allowed them to produce voiced sounds beyond their natural repertoire. This basic capacity is known as what allows human beings to learn the vowels of our mother tongues, as well as the new voiced sounds of second languages.

The study hence concluded that voice control in great apes differs from humans only in degree, not kind. Commenting on these ground-breaking results, the study’s lead researcher, Dr Adriano Lameira, has said that ‘language defines human communication, but its evolution defies scientific explanation. Great apes, our closest relatives, may hold the key to how language evolved in our lineage’.

Students planning to apply for Linguistics can consider how such research can contribute to helping us redefine our understanding of how spoken language may have evolved, more precisely by tracing these changes.