Rediscovery of Human Hands

828 Views

Charles Bell, a British surgeon, said, “We must confess that it is in this that we have the consummation of all perfection as an instrument.” Immanuel Kant, a German philosopher, regarded this as a visible part of brain, and Jacob Bronowski, a British mathematician, biologist, and historian of science, highly praised this as the “cutting edge of the mind.” What on earth is this?

This is the human hand. Actually, as the hand is very close to us as a part of our body, it is not getting much attention. However, if we just put on mittens, it is inconvenient to use the fingers for most activities and then we feel the importance of the hand.

The world with no hands

Without hands, the world experiences not only inconvenience. If we have no hands, the fields that need hands such as music, baseball, and basketball will disappear and we cannot play the instruments that require delicate movement of hands. Clothes shall have no buttons and zippers, and rings will be no longer needed. The bigger problem is that it is even impossible to maintain the present civilization, the achievement of mankind to date.

Number systems, which enabled human civilization to advance, also originated from the hands. Anthropologists consider that the mostly used decimal system (base 10), which has been found around the world, originated from ten fingers. Moreover, it is the dominant view that the duodecimal system and the sexagesimal system1 (base 60)2 started by counting the rest of finger joints with the thumb.

1. The duodecimal system is a positional notation numeral system using twelve as its base. For example, a dozen of pencils refer to 12 pencils, and a year is 12 months.

2. The sexagesimal system is a numeral system with sixty as its base. For example, it is used in measuring time; one hour of time is divided into 60 minutes, and one minute is divided into 60 seconds.

Five fingers, the consummation of perfection

How is the structure of the hand that made a great contribution to the development of human civilization? The human embryo’s hands are shaped like paddles. Soon, the cells between fingers disappear and ten fingers take shape. We usually repeat opening and clenching hands over 25 million times in our life time. On average men generate 121 lb [54.9 ㎏] of grip strength and women 70.4 lb [31.9 ㎏] of grip strength.

The hand consists of 8 bones in the wrist, 5 bones in the palm, and 14 bones in the fingers. The number of bones in both hands is a total of 54, which takes 25 percent among 206 human bones. And 25 joints that connect between bones and a lot of ligaments and muscles enable us to take 58 kinds of diverse motions; even a simple motion requires sophisticated coordination among the parts of the hand.

On our fingertips, there are fingernails that are made of tough protective protein. Fingernails serve an important function in manipulating small objects as they protect the sensitive tips of our fingers and support them. Thanks to the fingerprints on our fingertips, we can securely grasp objects with proper frictional force. As fingertips’ surface area increases, the number of sensory spot too increases and so helps us do more delicate work.

Anatomist Bernhard Albinus characterizes the thumb as the lesser hand, and Isaac Newton once said, “In the absence of any other proof, the thumb alone would convince me of God’s existence.” In comparison to primates (such as great apes or monkeys), humans have a 2.5-centimeter-longer opposable thumb. Thanks to this longer and independent thumb, humans can firmly grasp objects of various shapes. But if the thumb is longer than the middle finger, it is difficult to manipulate objects in detail though it’s possible to grasp them.

The most precise function that only the human hand is capable of is having the tip of the thumb touch the tip of the index finger. In case of Chimpanzee, the tip of the thumb can touch the tip of the index finger but it’s unstable and impossible to manipulate things delicately because its index finger is too long. Compared to animals, humans can make maximum contact between the two fingertips and even adjust the surface area. So, when we manipulate a small object, we can control the strength minutely or change directions freely.

When we play the piano or pound away at the keyboard, the five fingers can move freely thanks to flexible knuckle joints. By the way, why do we have five fingers? Chris Hays a British researcher asserted the answer in the New Scientist of 12 May, 2001, “Five is the magic number.” If animals grow more than five digits, he says, their other limb bones get distorted. No animals have six or more fingers. Panda’ sixth finger, or pseudo-thumb, is simply an enlarged radial sesamoid—a wristbone that was transformed. And the different length of human fingers enables us to take various motions. If we clench our fist with the little finger up, we can feel the strength grows weaker. This proves when we use five fingers, we can put forth strength most and do delicate operations. Like this, five fingers show the consummation of perfection.

Hand, a part of the brain

Developed hand motor functions are possible because of the neural control systems embodied in the sensory and motor pathways of the nervous system, which is connected from cerebrum to hand muscles. As cerebral signals are directly passed down to hand muscles, the brain actually controls finger muscles. What is more, as the proportion of cortical space devoted to the hand function is 30% of the whole brain, the words that the hand is a part of the brain exactly fit into place.

The hand actively makes the brain develop. Albert a German doctor asserted in the journal Nature that cortical space devoted to the hand function of those who read slate board grew wider. This supports that the brain was reorganized to receive the information provided by the hand. This implies that the action of clenching and opening hands can help baby’s brain development.

Hand, another eye

The feeling of cool water pouring onto the hand . . . The word, “WATER,” written on the palm! This was the moment when Helen Keller understood language for the first time. To her who was unable to see or hear, her hand was another eye. By touching objects with her hands and understanding the words written on her palm, she communicated with the world.

Such miracles can take place because Meissner’s corpuscles3 are found clustered beneath the ridges of the fingertips. Because of this, we can differentiate diverse sense of touch with the hand more precisely than any other parts of our body. Furthermore, as the hand is at the end of the long arm, we can search an out-of-the-way place, and also distinguish objects even in the darkness by feeling with it instead of seeing with eyes.

3. Meissner’s corpuscles are a type of mechanoreceptor. They are a type of nerve ending in the skin that is responsible for sensitivity to light touch. They are most concentrated in thick hairless skin, especially at the finger pads.

Like this, our hands are marvelous but we haven’t recognized this fact. Seeing elephants in a zoo eat food with their nose, we shout in excitement; seeing pandas grasp bamboo with their front paws, we admire. However, we have little interest in the capacity of our hands. Although we tap away at the computer and use the smart phone all day long, we even forget the fact that we’re relying on our hands in everything.

Edward, the protagonist of the film, Scissorhands, is an artificial man who has scissors for hands. As he has scissor hands, he cannot stroke the cheeks of his loving ones nor hug them. It happens not only in such a film but also in reality. Despite all of the advances in engineering and computer technology, though the newest robots have human-like hands and fingers, they cannot pick up things or control them as dexterously as human hands do. What makes it most difficult for scientists and engineers to make a perfect robot is to replicate a perfect human hand. The perfect hand, a masterpiece of the Creator, is very close to us.

Sources
John Russell Napier, Russell H. Tuttle, Hands, Princeton University Press, 1993
James Le Fanu, Why Us?: How Science Rediscovered The Mystery Of Ourselves, Pantheon, 2009