“Reach out and touch someone.” An action so simple as extending your index finger requires a complex network of finely integrated muscles, tendons, sensors, and processors to make it possible. This incredible work happens behind the scenes every second of the day, without our giving it a moment’s thought.

“When we look at animals from the outside, we are overwhelmingly impressed by the elegant illusion of design. . . . When we look inside, the impression is opposite. . . . It is a mess!”—atheist Richard Dawkins in The Greatest Show on Earth: The Evidence for Evolution (p. 371)

Some have suggested that the elegant designs in nature are merely illusions, fortunate outcomes of natural selection. If so, we would expect to find a confusion of haphazard, incomplete, and flawed structures. But when we look more closely at something as outwardly simple as extending a finger to type the letter u, we discover an astoundingly sophisticated design that points unmistakably to the Creator.

Seven Faithful Muscles

Seven muscles are required to control the index finger (Figure 1). Let’s contemplate each one briefly. The lumbrical muscle is a good place to start. Unlike most other muscles, which attach to bone, the lumbrical connects a tendon near the front of the index finger to a phenomenally complex shroud of delicate tendons and related tissues.

Seven Servants of Finger Motion

Click to enlarge

The lumbrical muscle serves two main functions—extending and retracting the finger in coordination with the other muscles.

These muscles must work closely together. The complexity of moving three finger bones in sync is hard to grasp. Imagine laying three steel bars on the ground end-to-end, and then tying the bars together with a series of wire harnesses. Pulling any one wire will affect the other wires. Now try moving all three bars together, side-to-side and up-and-down at the same time. You’ll quickly see how hard it is to keep everything in alignment.

Yet our index finger has no such problem. As the lumbrical muscle contracts, it reduces the tension on the long flexor tendon, while the lumbrical muscle simultaneously pulls on a ligament at the side of the finger, extending the finger (Figure 2). Sound complicated? That’s just a small part of the picture.

Several other muscles and tendons help control the positions of the finger bones. Consider the two long extensor muscle-tendon units. They split into three separate tendons over the first bone of the finger (Figure 3). The side tendons then shift above or below the second joint of the finger, depending on the degree to which the finger must be curled (or “flexed”).

Figures 2 and 3

Click to enlarge

Yet these tendons cannot straighten the finger by themselves. They need the simultaneous action of four other muscles: two interosseus muscles, located in the palm of your hand, and the long flexor muscle-tendon units located in the forearm. Without all these muscles working together, the finger bones would quickly become malpositioned and nonfunctional.

A “wonderfully integrated”1 relationship between muscles is required to bring about this desired motion.

Other finger motions require a different symphony of muscle movements. For instance, try shifting your finger sideways and forward, as though you are typing the letter y. The muscles interact in very different ways than when you type a u, but the motion can be just as smooth.2,3

The number of potential finger positions is virtually unlimited. If each of the seven muscles is capable of assuming one hundred different positions (and this is a conservative estimate) then the possible combinations would be 1x1014 or about 100 trillion. Yet our index finger can attain all of these positions with ease.

Keeping It All Straight

The finger’s tendons and ligaments have rightly been described as a complex, dynamic “net” that constantly shifts position in response to the multiple forces acting upon it. Can you imagine how complicated it must be to keep all these factors in balance?

Yet studies demonstrate that humans can exert such specific control of their muscles that they can direct a single nerve cell in the spinal cord to activate the few muscle fibers that the nerve cell controls.4 Additional nerve cells can be activated if a person wants to move an entire finger joint or alter tension in one muscle. This precise control enables microsurgeons to manipulate delicate instruments to repair arteries as small as one third of a millimeter in diameter.

Shifting the index finger from one computer key to another requires little conscious effort, but such activity demands simultaneous processing of hundreds of thousands of electrical signals. Nerve cells within the spinal cord receive signals from sensors in the hand that detect motion, stretch, and position. This information, together with visual input from the eyes, enables the nervous system to make instant calculations about the finger’s current position in space and immediately send new commands to multiple muscles to alter the finger’s position.

Digital signal processing did not originate with computers. It has been a part of our makeup since God created the first man, Adam. The monitoring system in our spinal cord and brain stem far surpasses anything humans have yet devised. The most advanced robotics research centers have endeavored to mathematically model finger motions in just two dimensions, with only limited success.5,6

By elaborate biochemical processes, sensors in the hand fire volleys of on-off signals to update the central nervous system about the hand’s status. If local anesthetics block these updates, then the patient will continue to perceive that the hand remains in the same position even if it moved. The central nervous system must continually reappraise incoming data to determine the positions of all voluntary parts.

This control system, which rapidly assesses incoming data from thousands of sources and then directs selected motors to respond, is apparently encoded in our DNA before birth. This “software” enables us not only to process a continuous stream of data but also to write new software subroutines that help us remember new finger motions as we practice them, whether learning to type or to play a musical instrument.

We even have special pre-installed programs to help us in emergencies. The withdrawal of a limb in response to contact with hot or sharp objects, for example, reveals this involuntary, unlearned programming, which smoothly and rapidly coordinates the action of multiple muscle groups. The physiologic process by which this “software” is written and the code is stored is not understood at all.

Effective functioning of the index finger requires not only well-orchestrated muscles, tendons, and nerves but also efficient processes to regulate blood flow, temperature, wound repair, growth, and immunity to diseases. The list goes on and on.

The Question of Origin

The index finger is capable of assuming at least 10 billion different positions with complete control.

Every part of our body, including our fingers, has a clear, integrated purpose. Detailed studies of hand anatomy have failed to identify a single structure devoid of function. Those who dismiss finger motion as simply the end result of a series of accidents have failed to appreciate the complex physiology involved.

Richard Smith, a noted hand surgery educator, once postulated that the first muscles to move fingers evolved within the hand proper. He stated that the forearm muscles appeared much later.7 Strangely, he did not acknowledge the fact that both groups of muscles must work together for effective hand function to occur.

Smith referenced the evolutionist Napier’s 1965 address to the Royal Society in London8 as evidence for the hand’s evolution and further speculated that the muscles within our hands are derived from the pectoral muscles of fish. This suggestion is implausible because recent studies have revealed that the amino acid sequences of structural proteins differ significantly among species.9

Napier’s address presented pictures of monkey and human hands and an unproved history of descent. His presentation, often quoted as authoritative, provides no evidence whatsoever of the evolution of the hand. Instead, it shows how a prior belief system drives our interpretation of the facts, even when they do not fit well.

When you look more closely under the surface of living things, one thing you don’t find is a mess. Those who deny the Creator expect to find disorder and invent levels of disarray and chaos that simply do not exist. Hand surgeons see that the finger extensor mechanism is intimidatingly complex and difficult to understand. Our best efforts in reconstructing a robotic hand pale in comparison to the structure and function of the original design.

Even the simple act of moving your finger from u to y on the computer keyboard reinforces the fact that we are fearfully and wonderfully made.

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Footnotes

  1. C. Harris and G. Rutledge, “The Functional Anatomy of the Extensor Mechanism of the Finger,” J. Bone Joint Surg. 54A, no. 4 (1972): 713. Back
  2. S. Sunderland, “The Actions of the Extensor Digitorum Communis, Interosseus and Lumbrical Muscles,” Am. J. Anat. 77 (1945): 189. Back
  3. R. Chase, “Muscle Tendon Kinetics,” Am. J. Surg. 109 (1965): 277. Back
  4. J. V. Basmajian, “Control and Training of Individual Motor Units,” Science 141 (1963): 440. Back
  5. E. L. Secco and G. Magenes, “Bio-Metric Finger: Human like Morphology, Control and Motion Planning for Intelligent Robot Prosthesis,” Mobile Robots, Moving Intelligence 325 (2006). Back
  6. F. J. Valero-Cuevas, “An Integrative Approach to the Biomechanical Function and Neuromuscular Control of the Fingers,” J. Biomechanics 38, no. 4 (2005): 673. Back
  7. R. J. Smith, Tendon Transfers of the Hand and Forearm (Boston: Little Brown, 1987), p. 103. Back
  8. J. R. Napier, “The Evolution of the Human Hand,” Proc. R. Soc. Lond. 40 (1968): 544. Back
  9. Y. K. Lin and D. C. Liv, “Comparison of Physical-Chemical Properties of Type 1 Collagen from Different Species,” Food Chemistry 99 (2006): 244. Back