Editor’s note: We are delighted to welcome the new book by award-winning British engineer and designer Stuart Burgess, Ultimate Engineering: An Engineer Investigates the Biomechanics of the Human Body (Discovery Institute Press), with an excerpt from Chapter 4.
Fingers have muscles fine-tuned for skillful moving. Each of the 34 individual muscles for the fingers of a hand contains individually controlled muscle sections called motor units. For example, the first dorsal interosseus muscle has around 140 motor units. That means each hand has thousands of motor units. Each motor unit has its own nerve pathway, which means the brain can guide the fingers to create very finely tuned forces by recruiting just one (or a few) muscle units.
The fine control of finger muscles that this affords helps explain why humans have such a delicate touch in areas like music, art, cooking, and surgery.
The design of the human brain also contributes to the extraordinary dexterity of our hands. The motor cortex is the part of the brain that controls the more than six hundred muscles around the body. Even though the hand muscles represent about 10 percent of the body’s muscles by number (and much less by mass), fully 25 percent of the motor cortex is dedicated to controlling the hand muscles. The extra brain space for the hands is required to store the complex patterns of muscle movement like the push-pull motion used in typing.
Superior to Robot Fingers
Human fingers are not just supremely dexterous; they are also remarkably robust. They can perform millions of movements over a lifetime of eighty years, heal from occasional injuries, and remain highly capable. Several top musicians have continued playing music at a professional level into their older age. At age ninety, German pianist Menahem Pressler played to a high standard with the Berlin Philharmonic and recorded albums of Mozart and Debussy.
Figure 4.4 shows an exoskeleton hand that my research group developed at Bristol University. It copies the cable-pulley system of the tendons in the human hand to flex and extend the fingers. We designed it to fit a particular patient who had recently suffered a stroke that severely weakened her right hand. We got to see the patient try it out, and it was very moving to see her regain the ability to hold objects by using our exoskeleton. The prosthetic device was good enough to dramatically improve her quality of life. At the same time, none of us involved in the project deluded ourselves: Our exoskeleton could only make simple hand grips, far short of what a healthy human hand could manage.
This wasn’t just a case of our prosthetic being behind the technology curve. In contrast to human fingers, robot fingers are, across the board, far less dexterous, far less touch sensitive, far bulkier and less robust. Comparing robot fingers to human fingers is like comparing a go-kart to a Formula 1 race car.
Evidence Points to Intelligent Design
So where does this leave us? We know robot fingers are intelligently designed. And yet we are told not to even consider the possibility that human fingers were intelligently designed and instead to trust evolutionary theory. But as we saw, there is a problem with that idea. Human hands possess a level of dexterity far beyond what is needed for survival tasks like tool-making or wielding a club, and therefore far beyond what we could expect a gradual evolutionary process guided by immediate fitness requirements to ever generate.
The level of skill that human hands demonstrate in areas such as art, music, and surgery is stunning. To be able to play 15 notes per second with one hand, and with precision, is not needed for survival. To be able to feel a ridge of 13 nanometers is also not needed for survival. The great skill of human hands is a case of what we will further explore later in the book: purposeful overdesign.
All notes may be found in the published book.