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One orangutan at the Indianapolis Zoo is giving researchers insight into human speech evolution.
Through observation, an 11-year-old orangutan named Rocky revealed an unknown level of vocal learning and control for the great apes.
The results—conducted by scientist Adriano Lameira in 2012 and published in “Scientific Reports”— go against the idea that orangutans have little power over their vocalizations, proving they are not only capable of learning new vocalizations—but controlling them in a social setting.
What does this change?
Then: Before the study, researchers thought great apes had little control over the sounds they made. They thought those vocalizations were just a response to something, like excitement, fear or food. It was also believed that those vocalizations had little to no variation in sound and pitch.
Now: After the study, researchers know apes are able to develop new vocalizations not within their existing vocabulary. They can also specifically control how they produce that new vocalization through volume and pitch.
Scientist Adriano Lameira observed Rocky with various social partners, taking turns making vocalizations like a conversation.
In the observations, Rocky instantly imitated the sound his human partner was making, including the vocalization’s soft or loud volume and low or high pitch.
By comparing these vocalizations to more than 12,000 hours of orangutan calls, researchers concluded Rocky’s sounds are much different than ones typically made by orangutans.
Rob Shumaker, the Indianapolis Zoo’s director and publication co-author, says the finding shows great apes are more cognitively sophisticated than many once thought.
“This is not very different than the statement that we used to hear that humans were the only species that used or made tools,” Shumaker said. “It was never true, but we had to learn that. I think this may be similar to that, where we thought humans were the only species that can acquire new vocalizations and directly control those vocalizations. It’s not true. We know that great apes can do that as well.”
"We thought humans were the only species that can acquire new vocalizations and directly control those vocalizations. It’s not true."
—Rob Shumaker, Indianapolis Zoo Executive Vice President Director
The study also calls into question human language evolution dates, as it was previously thought language started to emerge in great apes as long as 10 million years ago.
Now, Shumaker says the researchers think it was closer to 2 million years.
Rocky prompted the study after zoo researchers noticed the unique, “Star Wars” Wookiee-like sound he made toward humans for attention.
“It suddenly dawned on us—this is a brand new vocalization that no other orangutan has ever made, so this must be something that he can control,” Shumaker said. “We wanted to test that.”
Although the research is published, Shumaker says the zoo’s work is far from finished, as the Simon Skjodt International Orangutan Center team is investigating the findings by studying Rocky and other great apes at the zoo.
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