How did language begin? In crude depictions of early human life our ancestors are portrayed as monosyllabic grunters, communicating simple ideas with a few guttural grumbles.
But is this really how language evolved? A new study suggests not.
Publishing their findings in Proceedings of the Royal Society B: Biological Sciences, researchers from the University of Western Australia and the Australian National University outline their experimental support for an alternative theory of language evolution that focuses on the hands, not the mouth, as the birthplace of complex communication.
The primary function of language is to convey meaning, so the researchers argue that whichever non-verbal mode of communication – sound or gesture – is easiest to interpret is the one most likely to have been used as a precursor to oral language. Over the course of two experiments, the researchers aimed to test whether gestures or non-linguistic sounds were more effective at getting a message across.
“Basically, it’s a communication game, similar to charades, where people try to communicate a variety of words using either gesture or non-linguistic vocalisation – sounds that are not words,” says lead author Dr Nicholas Fay of the University of Western Australia.
“The interesting twist is that we had people play the game cross-culturally, with participants from both Australia and Vanuatu, and cross-experientially with blind and sighted participants.”
Their first experiment, which examined the influence of culture, tackled the question of universality. If gestures are the primary mode of language creation, say the researchers, then communication success should be higher for hand signals than for grunts both within and across cultures. Similarly, if gestures are a universal form of communication, then the spontaneous signals we come up with to convey meaning should be more similar in form than our vocalisations.
The results clearly supported gestures as superior conveyors of meaning, with twice as many words successfully communicated with hands than with noises.
More on language: More words don’t convey more information
In their follow-up experiment, the researchers then asked participants with severe vision impairments to follow the same procedure. People with very little eyesight can’t rely on socially learned gestures to convey meaning, so the kinds of gestures they create to represent words can tell us a lot about the importance of our physical interactions with the environment in developing language.
Incredibly, despite the much greater overlap in the auditory rather than visual environments of seeing and visually impaired participants, gestures continued to be significantly more successful than sounds in this second experiment. Indeed, visually impaired participants came up with gestures that were strikingly similar to those of sighted participants, despite their lack of shared experience.
“The visually impaired people are especially interesting because their success with gesture can’t be due to social learning,” says Fay.
“Instead, we argue that because they share the same body plan as sighted people and use their body to interact with and understand the world in similar ways, they represent the world in similar ways in the gesture modality, hence their success. For example, like sighted people, blind people often communicated the word ‘drink’ by manually simulating raising a container to their mouth and drinking from it.”
This holds true so long as we interact with our environment in similar ways, say the researchers. Despite strong commonalities, the influence of culture can be picked up for some words: participants from both Australia and Vanuatu used near-identical gestures to represent the word “lock” (miming the turning of a key) but differed in their displays for “chain” (where Aussies mimed the hauling of a heavy object, Ni-Vanuatuans simulated the throwing of an anchor, an action much more commonly used in their culture).
Although these new results add to a growing body of evidence that supports the gesture-first theory of language evolution, such as the similarities between gestures made by young children and those of chimpanzees, the researchers say the full picture is likely to be nuanced, with both gesture and speech together forming early communication systems.
All modern-day spoken languages have integrated gesture-systems. We don’t often think about them consciously, but the movements of our bodies add rich layers of meaning to our speech. But interestingly, some evidence suggests that while gesture aids speech, adding speech to gesture does little to improve communication success.
So why use an oral language at all?
“There are a variety of explanations for this, all of which are speculative,” says Fay.
“There is some evidence that speech is more efficient, so it makes sense for speech to take over from gesture once the communication system is established. The explanation I prefer is that, unlike the mouth, the hands are important to so many different activities, like cooking or childcare, that it makes sense for the mouth to take over and free the hands up.”
Jamie Priest is a science journalist at Cosmos. She has a Bachelor of Science in Marine Biology from the University of Adelaide.
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