How Did Humans Evolve to Use Everyday Tools?

An anthropologist explains why we experience many objects, from tennis rackets to cars, as extensions of our bodies

Roger Federer
Roger Federer hits a forehand shot at Wimbledon. The tennis great has called his racket an extension of his arm. Julian Finney / Getty Images

In the emerald countryside of Wales sits a manor named Nantclwyd Hall. Built 400 years ago, the luxurious two-story brick sanctuary is painted peach and capped with a gently sloping slate-gray roof. Surrounding it are acres of neatly geometric gardens, adorned with ornate temples and whimsical structures that stand like stone jewels amid long fields of trimmed grass.

One December evening in 1873, Nantclwyd Hall hosted a garden party. While staying at the manor, Major Walter C. Wingfield, an inventor and soldier who had served in India and then China during the Second Opium War, used the occasion to introduce a new game to his fellow guests. He called it sphairistike, roughly translated from ancient Greek for “the art of playing ball.”

Inspired by a ball game played indoors by aristocrats for centuries, Wingfield’s innovation was to move the game outside and replace the leather ball with a bouncing rubber one. The game was a hit. Within months, Wingfield had patented sphairistike. He began a business, published two books to promote the game and sold playing sets. Presented in a handsome, long wooden box, a typical set included written instructions, a long net, court markers, a rubber ball, pegs and tape to mark the court, and four lopsided rackets—to better to hit the low-bouncing ball. In the first year, Wingfield sold a thousand sets that quickly spread across the British Empire and beyond. Just three years later, in 1877, the first tournament of champions for lawn tennis, as the sport became known, was held at Wimbledon.

Although the major’s game of tennis is rarely recognized as a product of hominin evolution, the ability to strike a bouncing ball with a racket is evidence of an ancient symbiosis between human and tool. Consider what happens when you pick up a tennis racket the first time. At that moment, the racket is just a thing. An external object in the world. Next, a ball is tossed in your direction to strike. Perhaps you use both hands, keeping your feet firmly planted, and swing at the wrong angle, with the racket’s face parallel to the ground. You miss. But a coach gives you some instruction and then tosses another ball your way. Now you turn your body to the side, step forward, grip the racket at the right angle and swing to the ball with the racket’s wide face perpendicular to the ground. The racket releases a fulfilling thwock! The ball sails over the net.

With more practice, each swing becomes more natural, each ball hit more precisely as your hand feels ever more at home wrapped around the grip. As the literary scholar Steven Connor has noted in A Philosophy of Sport, one possible origin for the word “racket” is rachette, Middle French for the palm of the hand. This etymology suggests how the racket becomes a part of the hand itself. “If I wish the racket to become me,” Connor writes, “I must first become it.” Or, as one of the greatest living tennis players, Roger Federer, once said, “I love my racket, and it’s the extension of my arm, and it does all the magic for me.”

One study has shown how Federer’s sense of bodily extension is not magic but an acutely human experience. In 2017, researchers at the University of Genoa in Italy published a study in which they tested how tennis players perceived the space around their bodies when holding rackets. They had subjects hold their own tennis racket and then a racket they had never used before. The subjects were asked to verbally respond to a tiny electrical current to their hand and a random sound that was played by a speaker positioned at either the hand or the end of the racket. The purpose was to measure the subjects’ reaction time to the vibrations and sounds. When subjects were holding their own racket, they reacted much more quickly. This suggests that the subjects had embodied their own rackets more fully than the unfamiliar ones.

Such an experience is not limited to tennis rackets but includes every tool humans create and master: brooms, rakes, spoons, fishing rods, needles, saws, pencils, paintbrushes, saxophones, computer mice, prosthetics, wheelchairs and far more. We are all having this experience every day of our lives. We adopt tools as extensions of our arms, legs, eyes, brains and more as we navigate our daily to-dos. If you wear glasses every day, you are more likely to notice when you’re not wearing them than when you are.

How does this happen? One theory looks at what first happens to us as babies. Human infants are great explorers. We touch and feel everything. As we do this, we develop a sense of what belongs where. These explorations trace the topographies of our bodies and our relationship with things, how our bodies interact with the spaces and objects surrounding us. This theory posits that in the neocortex of a human child’s brain is something called a “somatosensory map.” This atlas of the body, as known through the senses, tells a child where skin ends and the world begins. Unlike most maps, though, this one is not fixed. It changes constantly and rapidly as we use things and then leave them behind. So, when a child wipes their nose, then scribbles with a crayon, then uses a wooden hammer to hit a pretend nail, the map of their bodies and tools is like a dry-erase board that is constantly being written and rewritten.

Sometimes we rewrite the map from necessity. After all, the human body itself is endlessly changing. Young people’s bodies flower; older people’s bodies decline. As an infant grows into an adolescent, the mind is endlessly adjusting to the body’s development—or trying to, if you’ve ever seen a stumbling toddler or gangly teenager. Through trial and error, and practice and repetition, with tools we can purposefully rewrite the map. The map is more than a metaphor. When a violinist practices six hours a day, they can increase the relative size of the area in their neocortex that corresponds to their fingers.

Another theory that explains how objects become part of our bodies is called “radical embodiment.” This view isn’t based on the idea of a map. Instead, objects become part of a whole, unconscious and dynamic human-thing system. This means that our brains actually perceive tools as literal parts of our bodies. When a person rides a bike, there is a beautiful unison where the person and bike become part of the person-bike machine. But a bike that has a flat tire, no handlebars and a broken chain becomes just a bike, and its rider becomes just a person. The same experience unfolds when a driver steps in and out of a car. “Not only do I incorporate the internal space of the car, such that pushing the brakes becomes as ‘natural’ a way of stopping to me as halting in my stride, but I incorporate the external space of the car; its power, velocity and acceleration,” the sociologist Nick Crossley writes. “When I park, overtake or pull onto a roundabout, for example, I ‘know without thinking’ how big the car is and how fast it will accelerate. I feel its size and speed as surely as that of my own body, moving only into those spaces in which I will fit and have the time to reach. I do not think about the car. I think as the car, from the point of view of the car.”

Another example is the person without sight who uses a cane. By tapping and touching, the sightless person does not feel the cane per se but the objects—the curb, the doorway—that are felt through the tool, in the same way sighted people experience these objects through their eyes. And so, in this line of thinking, embodiment occurs when there is a convergence between the tool and its user: The two become one.

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The underlying neural networks for these abilities evolved with the rise of mammals millions of years ago. After primates broke off into their own evolutionary branch, their sensorimotor systems became more elaborate than those of many other mammals. These changes happened long before Lucy’s folks picked up a stone and cut with it. The timing of these changes in the brain suggests to the neuroscientist Alison L. Barth that human “brains were built by ancient evolutionary processes that did not anticipate that we would pick up objects in our environment to extend our physical abilities.”

Aligning with Barth’s arguments, some paleoanthropologists have suggested that our ancestor hominins had relatively well-developed and integrated visuospatial and sensorimotor systems. That means that long before hominin brains started exponentially growing in size and hominin hands started making stone tools, the basic brain architecture for making somatosensory maps was already in place. Once tools were invented, our brains hijacked areas intended for other purposes to help us experience the magic of stretching our bodies into the world through tennis rackets, cars, bikes and canes.

The assimilation of tools into our bodies is fundamentally an inward, immersive experience. This can be seen in the rubber-hand illusion. For this experiment, a subject sits at a table in front of a box with two compartments. The first compartment has a transparent cover, under which is a fake rubber left hand. The second compartment has a nontransparent cover under which the subject puts their real left hand. A drape over the subject’s body helps complete the illusion, so that when the subject looks at the fake left hand it is positioned naturally where their mind perceives their real hand should be. The box is open to the researcher, who sits across from the subject.

A researcher then gently strokes the subject’s real fingers while also visibly stroking the rubber hand. After several minutes, the subject’s mind combines the visual information with the touching sensation and will come to feel that the rubber hand is actually their real hand. Just how real this sensation can be is demonstrated by when the researcher takes a nearby hammer and strikes the rubber hand; the subject often screams in pain because of the mind’s perceived link to the rubber hand. This points to how the map of our body is fluid, fundamentally shaped by physical experience as well as how the mind sees the body.

But the assimilation of tools into our bodies also works the other way: Tools extend and project us out into the world, doing what our bodies otherwise could not accomplish. Imagine a concert violinist who enjoys a sushi lunch, maneuvering a pair of chopsticks; then they practice all afternoon, dancing their bow across the violin’s strings; and then they leave their studio and pull a car out of the garage, swiftly backing up, anticipating what angle to turn the vehicle so that the side mirrors won’t strike the adjacent parked cars. The chopsticks extended their fingers by five inches. The bow lengthened their arm by 29 inches. The car extended their body to 14 feet. As the person expertly maneuvered each tool, their mind, without a conscious thought, allowed their body to grow—all to better eat, create music and transport itself—and then shrink back to its naked, tool-less size.

Finally, we can do this because the body’s experiences and the mind’s perceptions work together to quickly interpret the signals from the tools we use. When autumn comes and you rake fallen leaves, you know without even looking whether the rake’s metal tines are being pulled over grass or gravel. Through vibrations, the rake becomes an ersatz hand. In one study, research subjects tapped objects with a rod while both brain activity and rod vibrations were measured. Researchers found that the rod, on average, vibrated for about 100 milliseconds. But the somatosensory cortex often reacted within 20 milliseconds. In other words, well before the rod even stopped vibrating, the body’s touch sensors had already sent signals about the tool to the brain.

Another study—one looking at how professional athletes in China embody their equipment—made similar findings, though it measured this in experience rather than milliseconds. “The tennis racket is an extension of my arm and hand,” a 24-year-old player told researchers. “Judging from the [ball’s] vibration [as it strikes the racket], I know the ball’s power and spin, and then I can return it.”

Adapted from So Much Stuff: How Humans Discovered Tools, Invented Meaning, and Made More of Everything by Chip Colwell. © 2023 by Chip Colwell. All rights reserved. Reprinted with the permission of The University of Chicago Press.

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