Mimicking orangutan provides clues to early human speech

The mimicking abilities of an orangutan not unlike this one could provide clues as to how humans learned to talk(Credit: Kabir Bakie / C.C. 2.5)

It's generally assumed that great apes aren't capable of controlling their voices, and that our ability to do so couldn't actually have originated from them. But a Durham University study has turned that notion on its head, with evidence gathered from an adolescent orangutan strongly indicating that the species is, in fact, able to learn new sounds.

The research focused on a now 11 year-old orangutan, living at Indianapolis Zoo in Indiana. While being sure not to cause any major disruption to the animal's daily routine, the Durham team visited the great ape, named Rocky, in April and May 2012, and on several occasions since.

While with Rocky, the researchers conducted a simple, but extremely insightful test. While working with the ape, they made random sounds with varying tone and pitch. Fascinatingly, Rocky was then observed to mimic the sounds, repeating after the researchers in the same pitch and tone.

While that discovery might not immediately grab you as all that important, it actually contradicts long-term assumptions about the voices of great apes.

"Instead of learning new sounds, it has been presumed that sounds made by great apes are driven by arousal over which they have no control," said Durham University's Dr Adriano Lameira. "But our research proves that orangutans have the potential capacity to control the actions of their voices."

With the findings seemingly disproving the notion that our closest ancestors could not learn to produce new sounds, the research strongly indicates that our ability to speak – the very thing that sets us apart from the rest of the animal kingdom – did in fact stem from great apes.

The team compared recordings of the sounds made by Rocky with the largest available database of orangutan calls, containing sounds gathered from more than 120 apes, over 12,000 hours of observations of both wild and captive populations. The recordings of Rocky were found to be different to those in the database, supporting the notion that he learned the new sounds in a "conversational" context.

The research was published this week in the journal Scientific Reports.

Unsurprisingly, this isn't the only case of the study of nature providing clues to our own past. Take, for example, the recent Dartmouth study of the aye-aye – a type of prosimian – and its love of alcoholic foods. As it turns out, a genetic mutation shared by both those primates and humans could explain our own ancestors' love of alcohol.

Some of Rocky's vocalizations can be heard in the video below.

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