It’s not all in your head: How hands helped shaped human intelligence/cognition

The question of how humans develop our characteristic intelligence has traditionally been explained by our brains and its exceptional cognitive power. Recently, however, new theories and evidence of the evolutionary origin of human intelligence are discovering how  hands help the brain think in the way it does today.

While a strange idea at first, children clearly ‘think’ with their hands while learning to count and we all keep using them, like when trying to think of the fifth digit of our phone numbers, for example. Indeed, Vallée-Tourangeau [1] found that people working with manual models scored better than people working with a visual-only tablet option when solving arithmetic tasks. 

Similarly, James and Swain [2] found that children who actively interacted with objects while learning new words had larger brain activations and better performances in word-related tasks when compared to a similar group of children learning through passive observation. Lastly, even the word handle and its double meaning as the thing we use to open a door and the cognitive ability of handling a difficult situation tells the story of the intimate connection between hands and thought.   

In line with these simple examples, two long lines of research link hand dexterity – the ability to perform coordinated palm and finger movements – to the evolution of toolmaking and language, two key aspects of Homo Sapiens particular kind of intelligence.   

Approximately 2.5 years ago, and without any of our modern technology, it is evident how hands were a fundamental ingredient to start making tools. Less evident, however, is how the process of making tools might have also helped the evolution of other human assets such as memory, long-term planning, or social organization. 

To understand this idea, it is important to keep in mind that toolmaking is more than transforming raw materials into something else. To make an arrow out of a rock, for example, spatial memory is necessary to remember where the good rocks are, long term-planning is necessary to dedicate precious time to an activity with no immediate rewards, and social structure of older generations teaching the younger ones is necessary to show why, how, and where they should make arrows.

Conventionally, the story of this process started in the brain and finished in the hands. In other words, the toolmaking theory proposes  that humans first evolved bigger brains and then used the memory, planning, and social abilities derived from it to develop technology. 

Challenging this idea, however, Heldstab [3] compared how different species of primates develop hand dexterity and concluded that most infant primates use their hands in a similar way. With higher hand dexterity appearing in species with longer developmental periods – such as chimpanzees or humans – whose infants take a long time to develop the necessary skills of an adult. 

In evolutionary science, this kind of character, one that is shared among many species and with different developmental periods, is a well-known sign of ancient traits. Like mammary glands in mammals or gill in fish, dexterous hands appeared and stayed in primates long before human intelligence evolved. This evolutionary fact, alongside new research on chimp tool-use to crack nuts or fish for termites (see photo above), has transformed what we once knew about toolmaking. 

Specifically, if hand dexterity came before higher cognition and bodies came before brains (evolutionary speaking), how come we keep thinking that key markers of intelligence like toolmaking are the sole product of our brains?

Including the hands, the story of toolmaking evolution now considers not only the top-down mental mechanisms of brains directing the hands to make tools, but also the possibilities that the hands themselves offered to primates,  at least 30 million years ago. Namely, two dexterous limbs allowed us to discover and interact with the environment, imagine possibilities, and transform the environment surrounding us.

A second line of research examines the role of hands in communication and language. Although sign language and countless gestures make the expressiveness of hands hard to deny, the full extension of the  potential of the hands might not be so clear. 

While both sign language and gestures make use of hands to communicate, they do so in a different way, as seen in Goldin-Meadow [6] work with deaf children. In her study, she noticed that even when children had not been exposed to sign language, they spontaneously learned to use their hands in a language-like style: showing differentiation of words (e.g. nouns, verbs, adjectives), recombination (different ways of saying the same thing) and syntactic structure (sentence formation) in a different way than their speaking parents’ use of gestures. This outstanding skill suggests that, while in combination with speech, hands can complement speech by adding unspoken elements to it, in the absence of speech they can go as far as to functionally replace spoken language with hand signs. 

In an evolutionary approach that considered  the ancient origin of hand dexterity, researchers proposed a vital role of hands in the evolution of language. With further support of this idea, neurobiological evidence shows an overlap in the brain areas (Broca’s area; Figure 1) associated with hand-dexterity and language. This is evident in patients with both language disorders and reduced motor abilities in their hands [7]. 

According to this theory, language as we know it today evolved from a proto-sign language, which in turn derived from the primate tendency to imitate motor movements of other group members – much like children babble trying to imitate their parents’ words [8]. 

Like toolmaking, language also requires memory, future planning and a social structure to function. In other words, languages need consistent social groups to support the long periods where infants learn languages and languages profit from the long-term benefits a communication system offers to the social group. 

In this key aspect of human evolution, science is just starting to recognize what common language has long told us: being touched, in its metaphorical meaning, is more than the physical act and speaks to one of the most intimate forms of human connection.

Since hands are clearly integral to intelligence, it is time to acknowledge the full potential of our motor system and its ability to help shape and sustain some of our most precious cognitive abilities, like language and toolmaking. 

As Anaxagoras replied to Aristotle, “humans don’t possess hands because they are intelligent, they possess intelligence because they have hands”. So next time your brain feels overwhelmed, remember you also have two hands to help you think. Let’s all silence that inner voice saying ‘do not touch’ Let us touch, write, draw and count – exploring and imagining the world as our ancestors (and younger selves) did.  

References 

1. Vallée-Tourangeau, F., Steffensen, S. V., Vallée-Tourangeau, G., & Sirota, M. (2016). Insight with hands and things. Acta psychologica, 170, 195–205. https://doi.org/10.1016/j.actpsy.2016.08.006

2. James, K. H., & Swain, S. N. (2011). Only self-generated actions create sensori-motor systems in the developing brain. Developmental science, 14(4), 673–678. https://doi.org/10.1111/j.1467-7687.2010.01011.x

3. Heldstab, S. A., Isler, K., Schuppli, C., & van Schaik, C. P. (2020). When ontogeny recapitulates phylogeny: Fixed neurodevelopmental sequence of manipulative skills among primates. Science advances, 6. DOI: 10.1126/sciadv.abb4685

6. Goldin-Meadow, S. (2006). Talking and Thinking With Our Hands. Current Directions in Psychological Science, 15(1), 34–39. https://doi.org/10.1111/j.0963-7214.2006.00402.x

7. Ansar Uddin Ahmmed (2020) Manual dexterity and outcomes in a commonly used test battery to assess auditory processing disorder (APD) in children, Hearing, Balance and Communication, 18:2, 127-135, DOI: 10.1080/21695717.2019.1644862

8. Arbib M. A. (2005). From monkey-like action recognition to human language: an evolutionary framework for neurolinguistics. The Behavioral and brain sciences, 28(2), 105–167. https://doi.org/10.1017/s0140525x05000038