Roaming the dense jungles of South-East Asia, one might hear a distant call faintly resembling a beatboxer, but rather than emanating from a human, it might just be coming from an orangutan. The great apes have been heard producing vowel and consonant sounds at the same time – a complex feat even for us – shining light on the evolution of human speech.
Adriano Lameira at the University of Warwick in the UK and his colleagues recorded two groups of orangutans in two distinct locations in Indonesia for around 3800 hours.
The researchers found that female orangutans in Sumatra simultaneously make consonant-like kissing sounds and vowel-like hu-hooing sounds to warn their group if predators are around. Similarly, males in Borneo have a call that uses both mouth chomping and guttural grumbles that come from the larynx at the same time.
The sounds they make are striking and complex, says Lameira, comparing them to “beatboxing”. While two separate, far-away populations of orangutans are both employing these “bi-phonations”, it is still unclear whether all orangutans use these types of calls and whether this is a learned or innate facet of language, he says.
Research like this is “opening our eyes to the diversity” of speech patterns and abilities in species other than ours, says Marco Gamba at the University of Turin in Italy.
To better understand how humans have evolved our complex speaking abilities, researchers often look to songbirds, which also deploy similar bi-phonic techniques for their intricate communications. Yet the brain and vocal anatomy of birds are very different from those of humans, so it was hard to draw helpful parallels, says Lameira. Great apes might be that missing link.
“The traditional view is that great apes have very little interesting things to teach us about vocal communication,” says Lameira. “But with every new observation we actually start to build the most concrete image we ever had of what our own ancestors were doing and how it ultimately leads to us speaking right now.”