Human Speech Evolution: Orangutan Mimics Human Conversation

An ape at the Indianapolis Zoo is giving scientists insight into how human speech may have evolved across time. Scientists from Durham University in the United Kingdom discovered that orangutans might be able to control their voices after an eight-year-old orangutan named Rocky mimicked the pitch and tone made by researchers.

Rocky, now 11 years old, was studied from April to May in 2012 when researchers played a “do-as-I-do” game with the ape. Essentially, a researcher would make a random sound that varied in pitch and tone and Rocky would mimic the noise. The team then compared the more than sounds made by the ape with a database housing thousands of hours of clips of over 120 orangutans in the wild and captive.

By cross-referencing Rocky’s "mimic" vowel-like noises with the database, the researchers were able to verify that none of the "mimic" noises were found naturally within the orangutan population. Thus, the team was able to confirm that Rocky is capable of learning new sounds and controlling his voice instead of merely creating a "normal orangutan call with a personal twist."

"This indicates that the voice control shown by humans could derive from an evolutionary ancestor with similar voice control capacities as those found in orangutans and in all great apes more generally," said Adriano Lameira, who was not on staff during the time of the research but joined the team in 2015, in a university release.

Durham University has released recent footage of Rocky partaking in a game where he can learn more new sounds and further control his voice.

Prior to this study, published in the journal Scientific Reports, researchers debated the evolution of the spoken language and whether early human ancestors could make new noises.

"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, but our research proves that orangutans have the potential capacity to control the action of their voices," said Lameira. "This opens up the potential for us to learn more about the vocal capacities of early hominids that lived before the split between the orangutan and human lineages to see how the vocal system evolved towards full-blown speech in humans."