What do monkey gestures say about human language? Some argue the origin of human language lies in vocal calls while others nod towards gestures.
Animals do the most amazing things. Read about them in this series by Janaki Lenin.
If my husband wanted his back scratched, he’d instruct, “Little bit to the right. Go up.” Being humans endowed with language, we can communicate. People with hearing and speech disabilities use hand signals. Linguists use the term ‘reference’ for such verbal and sign communication. Researchers from India now reveal how bonnet macaques communicate without words.
An adult male bonnet macaque parted the fur of a female, picking nits and removing tangles. The latter held her tail out, and the male immediately started examining it. She displayed referential gesturing, like our use of words, say researchers.
When primates move their hands, heads, or bodies to signal to each other, it’s called a referential gesture, Shreejata Gupta, the main author of the paper, told The Wire. Such communication however simple requires complex cognitive ability until now thought to be possessed only by chimpanzees and bonobos in the wild.
In Kibale National Park, Uganda, wild chimpanzees scratch the part of their body where they’d like to be groomed. Their partners appear to know what the gesture means and proceed to comb the indicated spot. Many other species of primates gesture in captivity, but they haven’t been seen doing so in the wild.
Much of our understanding of gestural communication and the evolution of language is based on studies of African apes. “Other non-ape primate species have been largely ignored in this context,” says Gupta.
Gupta, then a doctoral student, and her supervisor, Anindya Sinha, of the National Institute of Advanced Studies, Bengaluru, say bonnet macaques are the only wild monkey species known to use gestures to communicate with their mates. She studied four troops of macaques for a year and a half at Bandipur National Park, Karnataka.
The researchers noticed the macaques using four distinct gestures to show where they wanted to be groomed. These included changing the position of the body or a body part, moving head or neck, and presenting their rear ends. Their partners got the message nearly 95% of the time. In the rest of the cases when their mates didn’t respond correctly, the macaques persistently indicated the itchy spot until their partners paid attention to it.
A sceptic might say the groomers poked around the closest body part. But the researchers show that on some occasions, the monkeys combed through the indicated section that was farther away from them.
A gesture has no value if the other animal doesn’t understand it. “When one macaque offers a body part, the other stops grooming and reaches the indicated spot, often putting itself in an awkward position,” Anindya Sinha told The Wire. “This is the clinching evidence for intentional referential gestures.”