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The Eye: A Classic Example of Natural Design

Cornelius Hunter
Photo credit: v2osk via Unsplash.

From Cicero in antiquity to John Ray three centuries ago, the eye has traditionally been held up as a marvel of design. Even Charles Darwin, after publishing his theory of evolution, privately admitted “The eye to this day gives me a cold shudder.” And it should have. Ray had extolled the many wonders of the human vision system, and since then those wonders have only continued to mount.

John Ray was a leading 17th-century botanist. He is remembered for formalizing the concept of the biological “species.” He is also remembered as the father of the 18th- and early 19th-century Natural Theology movement which emphasized nature’s designs. Ray’s study of the natural world led him to be increasingly impressed with its design. 

Myriad Examples of Design

Of Ray’s myriad examples of design, he paid particular attention to vision systems. The pupil, Ray noted, dilates and contracts in dim and bright conditions, respectively, to control the light entering the eye. That incoming light forms an image, but after passing through the lens of the eye it is inverted. Nonetheless, the nerves somehow present the image “in its right or natural Posture” to the soul.

Those nerves are bundled together, forming the optic nerve which runs through the retina and back to the brain. And while it may seem logical for the optic nerve to run through the center of the retina, directly behind the lens, in fact it is off to the side, for improved vision. And the images from the two eyes are combined to form depth perception.

Six muscles provide fast and accurate rotation of the eye “to move it upward, downward, to the Right and Left, obliquely and round about,” to direct one’s field of view without requiring head motion. These and other features led Ray to conclude that the eye was designed, for it was “highly absurd and unreasonable to affirm, either that it was not Design’d at all for this Use, or that it is imposible for Man to know whether it was or not.”1

Two Warnings

To those who would dismiss these ideas as the outdated musings of an early scientist, I have two warnings. First, beware of presentism — the anachronistic judging of the past according to contemporary facts and sentiment. It can mask the wisdom of those who came before and lead to a false confidence. Your 21st-century facts do not necessarily make you superior to intellectual giants of previous eras.

Second, far from refuting Ray’s three-hundred-year-old work, those 21st-century facts have, indeed, done much to amplify Ray’s conclusions. For if the 18th-century study of vision suggested design to thinkers such as Ray, then our 21st-century knowledge is screaming design. If you believe the times have changed, and Ray’s ideas are now outdated and outflanked, then you really don’t understand the science.

Design on Steroids

Today we have a picture of design on steroids that Ray could not have dreamed of. For example, we now have insight into cellular signal transduction and the vision cascade. Light impinging on the retina enters photoreceptor cells and interacts with a small chromophore molecule, altering its configuration. That shift sets off an intricate cascade of events. Like a tail wagging the dog, the altered chromophore influences a much larger opsin protein which, in turn, activates hundreds of transducin molecules which next activate enzymes that degrade hundreds of thousands of the cyclic nucleotide, cGMP, molecules.

The reduction in cGMP concentration causes the closure of membrane proteins, thus shutting out millions of sodium ions per second that otherwise would have entered the cell. The reduced inflow of sodium ions causes a shift in the voltage across the photoreceptor cell membrane which reduces the release of neurotransmitter in the synaptic region of the cell. This can initiate an electrical signal that ultimately will be transmitted to the brain.

Only the Beginning

This remarkable, finely tuned, intricate, and interdependent cascade provides incredible sensitivity in low-light conditions. Twentieth-century researchers were stunned to discover that we are capable of sensing even just a few photons. But this description of the vision cascade is only the beginning. For example, also in the retina are Mueller cells which simultaneously perform multiple functions. First, they help to sustain the photoreceptor cells and provide mechanical support to the neurons carrying signals to the brain. But secondly, they serve as biological waveguides, guiding the incoming light to the right photoreceptors, depending on light intensity and wavelength. The result is far greater optical efficiency. As one researcher explained, the retina’s “optical structure is optimized for our vision purposes.”2

This is only a tiny introduction to the design of our vision system. And although it hardly needs to be said, not only does evolution lack a credible explanation for how such designs evolved, but the various components, such as the chromophores and opsins, do not fall neatly into an evolutionary pattern. We can see that Ray’s 18th-century sentiment, that it was “highly absurd and unreasonable to affirm” the eye was not designed, was not the musings of an old scientist, but a presaging of things to come.

Notes

  1. Ray, John. 1977. The Wisdom of God Manifested in the Works of the Creation, 7th ed. New York: Arno Press. First published in 1717.
  2. EurekaAlert!, 2/27/2015, “Mystery of the reverse-wired eyeball solved,” AAAS, https://www.eurekalert.org/news-releases/817813.