What hand gestures tell us about the evolution of language

Imagine that you are visiting a food market abroad and you want to buy a slice of cake. You know how to say “hello” in the native language, but otherwise your knowledge of the language is limited.

When it is your turn to order, you greet the vendor and point at the cake of your choice. The vendor then places his knife on the cake and looks at you to see if you approve of the size of the slice. You quickly shake both of your hands and indicate that you would like a smaller width for the slice using your thumb and index finger. The vendor then cuts a smaller piece for you and you happily pay for your cake. In this example, you achieved successful communication with the help of three gestures: a pointing gesture, a conventional gesture, and an iconic gesture.

As humans, we are the only species that engage in the communication of complex and abstract ideas. This abstractness is even present in a seemingly simple example such as indicating the size of a slice of cake you desire. After all, size concepts such as ‘small’ and ‘large’ are learnt during development. 

What makes this sort of communication possible are the language and gestures that we have at our disposal. How is it that we came to develop language when other animals did not, and what is the role of gesture in this? In this blogpost, I introduce one historically dominant theory about the origins of human language – the gesture-primacy hypothesis (see Hewes, 1999 for an historic overview).

According to the gesture-primacy hypothesis, humans first communicated in a symbolic way using gesture (eg movement of the hands and body to express meaning). Symbolic gestures are, for example, pantomimes that signify actions (eg, shooting an arrow) or emblems (eg, raising an index finger to your lips to indicate “be quiet”) that facilitate social interactions (McNeil, 1992; 2000). 

The gesture-primacy hypothesis suggests that spoken language emerged through adaptation of gestural communication (Corballis, 2002, Hewes, 1999). Central to this view is the idea that gesture and speech emerged sequentially.

Much of the evidence in favour of the gesture-primacy hypothesis comes from studies on nonhuman primates and great apes. Within each monkey or ape species, individuals seem to have the same basic vocal repertoire. For instance, individuals raised in isolation and individuals raised by another species still produce calls that are typical for their own species, but not calls that are typical for the foster species (Tomasello, 2008, p. 16). 

This suggests that these vocal calls are not learned, but are innate in nonhuman primates and great apes. Researchers believe that controlled, complex verbal communication (such as that found in humans) could not have evolved from these limited innate communicative repertoires (Kendon, 2017). This line of thinking is partly confirmed by failed attempts to teach apes how to speak, and failed attempts to teach them to produce their own calls on command (Tomasello, 2008, p. 17).

However, the repertoire of ape gestures seems to vary much more per individual than the vocal repertoire (Pollick & de Waal, 2007), and researchers have succeeded in teaching chimpanzees manual actions with the help of symbolic gestures that were derived from American Sign Language (Gardner & Gardner, 1969). Moreover, bonobos have been observed to use gestures to communicate more flexibly than they can use calls (Pollick & de Waal, 2007). The degree of flexibility in the production and understanding of gestures, especially in great apes, makes this communicative tool seem a more plausible medium through which language could have first emerged than vocalisation.

In this regard, it is notable that great apes that have been raised by humans point at food, objects, or toys they desire. For example, some human-raised apes point to a locked door when they want access to what’s behind it, so that the human will open it for them (Tomasello, 2008). It is thus clear that human-raised apes understand that humans can be led to act in beneficial ways via attention-directing communicative gestures. 

Admittedly, there does seem to be an important type of pointing that apes seem incapable of; namely, declarative pointing (ie, pointing for the sake of sharing attention, rather than merely directing attention) (Kendon, 2017). Nonetheless, gesture seems to be a flexible and effective communicative medium that is available to non-human primates. This fact, and the fact that vocalisations seem to be relatively inflexible in these species, play a significant role in making the gesture-primacy hypothesis a compelling theory for the origins of human language.

What about human evidence that might support the gesture-primacy hypothesis? Studies on the emergence of speech and gesture in human infants show that babies produce pointing gestures before they produce their first words (Butterworth, 2003). Shortly after their first birthday, when most children have already started to produce some words, they produce combinations of pointing gestures (point at bird) and one-word utterances (“eat”). These gesture and speech combinations occur roughly three months before producing two-word utterances (“bird eats”). 

From an ontogenetic standpoint, then, referential behaviour appears in pointing gestures before it shows in speech. Many researchers therefore consider gesture to pave the way for early language development in babies (Butterworth, 2003; Iverson & Goldin-Meadow, 2005).

Further evidence concerns the spontaneous emergence of sign language in deaf communities (Senghas, Kita, & Özyürek, 2004). When sign language is passed on to new generations, children use richer and more complex structures than adults from the previous generation, and so they build upon the existing sign language. 

This phenomenon has led some researchers to believe that the development of sign language over generations could be used as a model for the evolution of human language more generally (Senghas, Kita, & Özyürek, 2004). The fact that deaf communities spontaneously develop fully functional languages using their hands, face, and body, further supports the gesture-primacy hypothesis.

Converging evidence also comes from the field of neuroscience. Xu and colleagues (2009) used functional MRI to investigate whether symbolic gesture and spoken language are processed by the same system in the human brain. They showed participants meaningful gestures, and the spoken language equivalent of these gestures.

The same specific areas in the left side of the brain lit up for mapping symbolic gestures and spoken words onto common, corresponding conceptual representations. Their findings suggest that the core of the brain’s language system is not exclusively used for language processing, but functions as a modality-independent semiotic system that plays a broader role in human communication, linking meaning with symbols whether these are spoken words or symbolic gestures.

In this post, I have discussed compelling evidence in support of the gesture-primacy hypothesis. An intriguing question that remains unanswered is why our closest evolutionary relatives, chimpanzees and bonobos, can flexibly use gesture, but not speech, for communication. 

Further comparative studies could shed light on the evolutionary history of the relation between gesture and speech. One thing is certain: gesture plays an important communicative role in our everyday lives, and further studying the phylogeny and ontogeny of gesture is important for understanding how human language emerged. And it may also come in handy when ordering some cake on your next holiday!

References

Butterworth, G. (2003). Pointing is the royal road to language for babies. In S. Kita (Ed.) Pointing: Where Language, Culture, and Cognition Meet (pp. 9–34). Mahwah, NJ: Lawrence Erlbaum Associates.

Corballis, M. C. (2002). From hand to mouth: The origins of language. Princeton, NJ: Princeton University Press.

Gardner, R. A., & Gardner, B. (1969). Teaching sign language to a chimpanzee. Science, 165, 664–672.

Hewes, G. (1999). A history of the study of language origins and the gestural primacy hypothesis. In: A. Lock, & C.R. Peters (Eds.), Handbook of human symbolic evolution (pp. 571–595). Oxford, UK: Oxford University Press, Clarendon Press.

Iverson, J. M., & Goldin-Meadow, S. (2005). Gesture paves the way for language development. Psychological Science, 16(5), 367–371. Doi: 10.1111/j.0956–7976.2005.01542.x

Kendon, A. (2017). Reflections on the “gesture-first” hypothesis of language origins. Psychonomic Bulletin & Review, 24(1), 163–170. Doi: 10.3758/s13423-016‑1117‑3

McNeill, D. (1992). Hand and mind. Chicago, IL: Chicago University Press.

McNeill, D. (Ed.). (2000). Language and gesture. Cambridge, UK: Cambridge University Press.

Pollick, A., & de Waal, F. (2007). Ape gestures and language evolution. PNAS, 104(19), 8184–8189. Doi: 10.1073/pnas.0702624104

Senghas, A., Kita, S., & Özyürek, A. (2004). Children creating core properties of language: evidence from an emerging sign language in Nicaragua. Science, 17, 305(5691), 1779–82. Doi: 10.1126/science.1100199

Tomasello, M. (2008). The origins of human communication. Cambridge, MA: MIT Press.

Xu, J., Gannon, P. J., Emmorey, K., Smith, J. F., & Braun, A. R. (2009). Symbolic gestures and spoken language are processed by a common neural system. PNAS, 106(49), 20664–20669. Doi: 10.1073/pnas.0909197106