Mothers of Invention

Look at your hand. Hold it up. Flex it. Bend it. Make it act like a puppet. It’s a remarkable piece of engineering. Never before have five digits, fourteen joints, and twenty-seven bones come together in such an interesting and practical way. If you turn it, eight cube like bones connected by a matrix of tendons in your wrist and forearm enable you to rotate your hand 180 degrees. This makes it possible to do things that animals in the natural world, even if they had the inclination, could never possibly carry off, like a swing a baseball bat, pour a glass of milk, play a Duke Ellington piano solo, or paint a portrait.

The fingers of our hands actually have no muscles. They operate by remote control, like marionettes. A web of tendons, anchored in the palm, midforearm, and as far north as the shoulder are the strings that make your digits dance. The whole arrangement provides our hands with an unusually wide range of motion. But anatomical feature that renders your hand especially special is your first digit, its version of a big toe: your thumb.

One of the great beauties of our thumb is their position. Whereas our feet forsook the thumblike position of their first digits and evolution straightened them into one big toes, our hands did not. In fact, they went in the opposition direction, building on their former status as feet specialized for climbing and grasping.

This is why our hands still look remarkably like a gorilla’s foot, with our thumbs sitting down before the other four digits, positioned apart, as if they were reluctant to join the rest of the group. Not that this means, however, that thumbs in any way evolved to play second fiddle to the rest of our fingers.

Compared with the thumbs of other primates, our have acrobatic ranges of motion. Chimp thumbs for example, can’t rotate in great swirling arcs like a human thumb, and that limit their ability to be the thing that all thumbs secretly long to be…opposable. O sau “limits” because, contrary to popular belief, the thumbs of chimps and monkeys are opposable. They just aren’t in the same peculiar way that ours are. What is different is that we can effortlessly swing our thumbs across the palms of our hands to meet our small and ring fingers, and fourth and fifty digits. Nothing like this exists anywhere else in nature. It’s called the ulnar opposition, and this seemingly simple ability gives our hands the power to grasp and grip, turn and twist, manipulate and touch in ways foreign to other creatures. Because of this ability we can pick up and use a hummer or an ax, or turn a stick into a lethal club by cupping it in a position that extends the power of our arm, and, with it, the force of the blow it delivers. It is one thing to flail a stick horizontally for show, like a chimpanzee, another to grip it along the axis of your forearm and bring it down from on high with bone-crushing force.

…………

These abilities exist because we have developed specialized tendons linked to our thumbs. One, a flexor called the pollicis longus, runs from the thumb’s knuckle all the way to the shoulder. Along with three other muscles, it lets us push and mash things as well as open our hands and spread our thumbs away from our palm, movements that come handy when operating a joystick, typing on a keyboard, or thumbing in the numbers on a cell phone. But it is also very useful for gripping and manipulating sticks and stones, natural artifacts that our ancestors used to fashion the first tools into axes, spears, and small knives more than two million years ago.

It’s not simply the speed and flexibility of our thumbs, fingers, and hands that make them special. It’s also their extraordinary sensitivity. Crammed within every square inch of our digits are nine thousand hypersensitive egg-shaped, buds called Meissner’s corpuscles, which lay just below the epidermis, our outermost layer of skin. Inside each but like coiled nerves that sense and snatch up the signals initiated by whatever we touch and send it to the brain for processing. …………. They’re optimized for gathering the finest, most granular pieces of sensual information, and they are why our hands are, as Sir Chalres Bell, put it, “so powerful, so free and yet so delicate.”

Without this combination of dexterity and sensitivity, Michelangelo would never have been able to sculpt the face of his Moses, nor Leonardo paint ‘The Last Supper’. Horowitsh could not even plunk out the most juvenile version of the Emperor Concerto, and Shakespeare would have been incapable of grasping a quill to pen a single word of the thousands he invented for the English language.

The point here is a subtle one. The physical power and dexterity of our thumbs and hands make them central to our humanity. Their biological evolution literally changed our minds. They enabled us to better manipulate the world around, and the manipulation of things then came to also mold our minds. This is what prompted novelist Robertson Davies to observe in his book “What’s Bred in the Bone,’ “the hand speaks to the brain as surely as the brain speaks to the hand.” The writing for creativity, fo memory, for emotion, and above all (as we shall see) for language, exist largely because or thumb came first, and in orchestrating our physical conversations with the world, laid the neural ground work for the peculiarly human mind that would follow. Our thumbs are that defining. Without them, we wouldn’t be human. We would be something else.

For the ancestral line of apes that led to us, there would have been a considerable evolutionary advantage in developing thumbs. As they gave up knuckle-walking and spent more time upright, their hands would have been freed to hold more, carry more, throw more, and eventually manipulate and make more. Had early savanna apes not begun walking upright, thumbs would never have evolved. And if they had not, we wouldn’t have either. ~ Pages 46 – 48)