Before most of us could talk, we were communicating with gestures — holding, pointing and reaching at objects, for example, to communicate our wants and needs to others.
These referential gestures (known as deictic gestures to those in the know) are thought to play an important foundational role in the development of higher forms of communication like speech, and are believed to be relatively rare in the animal kingdom. But now, scientists have found the first evidence that ravens, widely recognized as some of nature's smartest birds, use deictic gestures too — a discovery that researchers say could help shed light on the mysterious origins of human language.
Until recently, deictic gestures had only been observed in humans and a few of our closest evolutionary relatives, like chimpanzees — who have been observed signaling to other chimps where on their bodies they would like to be groomed. But according to researchers Simone Pika and Thomas Bugnyar (experts in gestural communication and raven behavior, respectively), virtually nothing is known about comparable skills in non-primate species.
In the interest of filling this investigative gap, Pika and Bugnyar spent two years observing the social interactions of seven pairs of ravens to determine if the birds engaged in referential gestures similar to those seen in humans. They discovered that ravens will use their beaks to present their counterparts with moss, stones and twigs; that these gestures are typically directed towards ravens of the opposite sex; and that they are only performed when another bird is watching.
In the latest issue of Nature Communications, Pika and Bugnyar conclude that these gestures may function as "testing-signals," allowing a raven to evaluate the interest of a potential partner, or to reinforce the strength of an already existing bond.
"If communication is governed by cooperation, then this could be what prompted the evolution of language [in both humans and ravens]" explains Pika. She continues:
Gesture studies have too long focused on communicative skills of primates only. The mystery of the origins of human language, however, can only be solved if we look at the bigger picture and also consider the complexity of the communication systems of other animal groups.