A study published last month in the journal Animal Cognition looked at gestural communication and its cognitive and developmental bases in a wild population of bonnet macaques, a monkey species endemic to peninsular India.
Bonnet macaques were found to employ four different gestures to solicit grooming from other monkeys and even to indicate the parts of their bodies they want groomed.
This might be an indication that primitive language-like capacities arose in the primate lineage even before apes evolved, since Bonnet macaques are Old World monkeys, which are evolutionarily older than the anthropoid apes.
Scientists seeking to understand the origins of human language have long known that ape’s communicative gestures share striking similarities with those of humans. These gestures are believed to shed light on just how symbolic representation through language might have emerged in the primate lineage in the first place.
Apes gesture with their limbs and bodies to communicate with other members of their species, just as we humans do. Scientists have even found evidence that apes can use indicative gestures to refer to other objects in order to achieve some goal — for instance: “Don’t scratch me there, scratch me here.” Thus, referential gesturing can direct the attention of the receiver to the sender’s object of interest or desired outcome.
These “indicative gestures” require a much more complex understanding of others as intentional beings for effective communication to be achieved. But recent research on a range of species has suggested that the sorts of sophisticated cognitive skills necessary for indicative gesturing, which scientists widely consider to be the precursor to symbolic language in humans, may not have arisen solely in our closest ape relatives — and might have even older evolutionary roots than was previously believed.
For instance, a study published last month in the journal Animal Cognition looked at gestural communication and its cognitive and developmental bases in a wild population of bonnet macaques, a monkey species endemic to peninsular India.
Shreejata Gupta, a post-doctoral researcher at Duke University in the United States, and Anindya Sinha, a professor at the National Institute of Advanced Studies in Bengaluru, India, found that bonnet macaques employ four different gestures to solicit grooming from other monkeys and even to indicate the parts of their bodies they want groomed. The recipient of these gestural communications understood the intention, too, Gupta and Sinha said, as they immediately began to groom the indicated body part, even if it meant stretching awkwardly or changing positions to do so.
Such indicative gestures in the context of grooming amongst individuals of the same species, the researchers note, have been reported earlier, in various primates raised by humans and even in wild chimpanzees, but never from any monkey species living in the wild.
There are two important aspects of primate communication that have been studied over the years, Gupta explained to Mongabay: vocal communication and gestural communication. Vocal communication has mostly been explored in non-ape species, while gestures have mainly been studied among the apes.
“What we now understand, summarizing rather simply, is that primate gestures appear to lie at the roots of human language evolution, [with] this hypothesis largely supported by evidence of shared neuronal and cognitive underpinnings,” Gupta said.
But past studies have generally not examined non-ape primate species and their communicative gestures, which could help further our understanding of shared language-like capacities across the entire primate lineage and pinpoint their origins more precisely. “Our study is possibly a first step towards fulfilling this gap,” Gupta added.
It has traditionally been accepted that the fairly sophisticated abilities required to produce referential gestures were restricted to humans and to apes, our closest phylogenetic kin. But Gupta said that recent studies have systematically examined and found such abilities in other species, including dolphins, some coral reef fish, horses, and ravens.
Using methodologies that are typically used to study ape gestures, Gupta and Sinha were able to show that similar communicative behaviors are exhibited by the bonnet macaque, an Old World monkey species. That could mean that the roots of human language stretch even farther back into history than we thought.
“Our study clearly illustrates that wild bonnet macaques possess the ability of referentially gesturing towards one another, an indication that such primitive language-like capacities arose in the primate lineage even before apes evolved, Old World monkeys being evolutionarily older than the anthropoid apes,” Gupta said.
- Gupta, S., & Sinha, A. (2016). Not here, there! Possible referential gesturing during allogrooming by wild bonnet macaques, Macaca radiata. Animal Cognition, 1-6. doi:10.1007/s10071-016-1012-3