Blog

by Steve Risner

To see or not to see—that is the question. We have eyes. They're amazing. Lots of organisms have the ability to sense light in a variety of degrees, from the difference between light and dark to the Mantis shrimp who has 16 different photoreceptors (compared to our 3 or a dog's 2) and can see in ways we can hardly imagine. The eye's anatomy has been studied in detail since the first century AD, so Charles Darwin had no issues with the structure of the eye when he wrote about the theory of evolution. However, since that time, much has been learned about the biochemical systems that give us sight. It's truly astounding and makes it very difficult to believe the anatomical structure we call the eye arose by accidents in genetic copying. I say “difficult” rather than impossible because, although it seems crazy, many believe in the evolution of the eye through random mutational changes. This is similar in idea to the fact that, in Darwin's day, the indescribable complexity of a living cell was unknown. It was easy for Darwin to see a tiny bag of goo and believe it evolved over time. But to now know a fraction of the complexity of the cell and believe it arose by accident is mind blowing for me. But, back on topic...

In The Origin of Species Charles Darwin wrote:
To suppose that the eye with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest sense (1859, p. 170).

But even though Darwin acknowledged that the eye could not have evolved, he went on to argue that it had, in fact, been produced by natural selection through an evolutionary process. Interestingly, natural selection gives absolutely no mechanism by which the parts necessary for vision came about—only how they remained. Let's take a closer look.

The human eye is, on average, an inch across (not nearly as large as the Colossal Squid's which is nearly a foot across), weighs about ¼ of an ounce, and has many parts—all of which are necessary for good vision. Stick with me here. These parts include the sclera, cornea, anterior and posterior chamber, iris, lens, vitreous humor, retina, fovea, and macula, not to mention the various muscles that cause the pupil to expand or contract, the lens to focus, or the eyes to move about. Let's also not forget to at least mention ducts and glands as well as eye lids and eye lashes which all have very important functions. Let me briefly describe each part so we can see just how amazing this structure is.

The sclera is the white of the eye and has muscles attached to it. The cornea is the main refractor of the eye and is the small bulge that sits off of the front of the eye. Humans and sharks have very similar corneas (because of a common ancestry I suppose), so shark corneas are used in transplants on occasion. The anterior/posterior chambers are between the cornea and iris and iris and lens respectively and are filled with the aqueous humor, which gives the area nutrients as well as creates pressure to give the eye its shape. The iris is the colored portion of the eye (most commonly brown) and contains the pupil. The pupil is simply a hole in the center of the iris, which determines the amount of light that can pass into the eye. We then have the lens, which is layered like an onion and changes shape to allow us to focus on different objects. It can do this faster than any camera made today. The vitreous humor is in much larger supply compared to the aqueous humor and fills the space behind the lens. It is a gelatinous substance that provides nutrients to the eye and is between the lens and retina. The retina contains all of our photoreceptors—about 100 million light sensitive cells in each eye. The human eye can see about 10,000,000 colors, all just dependent on red, blue, and green. In terms of a camera, the eye is just about 576 megapixels. Not bad for “Mother Nature” to produce on accident, huh? The fovea is in the center of the retina and is the most visually acute portion of the retina. There are no black and white receptors here—only color. And, finally, the macula is a protective covering for the retina. It plays a role in keeping out damaging radiation. We have a pair of eyes, which gives us depth perception. Our eyes can see a single candle burning 14 miles away. If any of these parts is damaged or missing, vision would be impaired, if possible at all. And we've not discussed anything that actually happens to give us sight.

The “blind spot” is called the optic disc and is the area of the retina where the optic nerve leaves the eye and is void of photoreceptors. Each optic nerve includes ¾-1¾ million nerves. These nerves (which are technically an extension of the brain and not nerves) carry messages to the back of the brain where the visual cortex is located. A great deal of brainpower is used for sight. It's truly a marvel. Man has yet to create such a device, and transplants of the eye are a long way off because of the complexity involved in these structures.

Some argue in favor of this engineering wonder being a product of chance and mutation. Darwin arranged a great number of seemingly “simple” eyes in a succession and suggested it was a possible route by which our eyes evolved. As previously stated, a “simple” eye is anything but. You see, a simple light sensitive spot is extremely complicated, involving a huge number of specialized proteins and protein systems. These proteins and systems are integrated in such a way that if one were removed, vision would cease. What I'm saying is for the miracle of vision to occur, even for a light sensitive spot, a large number of different proteins and systems would have to evolve simultaneously, because without them all there at once, vision would not occur. Why would an organism keep any structure necessary for vision if they all were not present?

Dr. Behe explains the “simplest” eyes for us: the first step in vision is the detection of photons. In order to detect a photon, specialized cells use a molecule called 11-cis-retinal. When a photon of light interacts with this molecule, it changes its shape almost instantly. It is now called trans-retinal. This change in shape causes a change in shape of another molecule called rhodopsin. The new shape of rhodopsin is called metarhodopsin II. Metarhodopsin II now sticks to another protein called transducin, forcing it to drop an attached molecule called GDP and pick up another molecule called GTP. The GTP-transducin-metarhodopsin II molecule now attaches to another protein called phosphodiesterase. When this happens, phosphodiesterase cleaves molecules called cGMPs. This cleavage of cGMPs reduces their relative numbers in the cell. This reduction in cGMP is sensed by an ion channel. This ion channel shuts off the ability of the sodium ion to enter the cell. This blockage of sodium entrance into the cell causes an imbalance of charge across the cell's membrane. This imbalance of charge sends an electrical current to the brain (a nerve impulse). The brain then interprets this signal and the result is called vision. Many other proteins are now needed to convert the proteins and other molecules just mentioned back to their original forms so that they can detect another photon of light and signal the brain. If any one of these proteins or molecules is missing, even in the simplest eye system, vision will not occur. Pretty simple stuff, right? It's almost comical to read such a paragraph and, if we can grasp it, realize someone wants us to believe this came about through an undirected, unknown process, which is nothing more than copying mistakes. But, as Proverbs 20:12 says, “The hearing ear and the seeing eye, the Lord has made them both.” A Designer is absolutely necessary for the eye to exist in any of its various forms. Rather than give credit to a fictitious process, let's praise God and marvel at His creativity and wisdom.

Alan Gillen explained it well when he wrote: “No human camera, artificial device, nor computer-enhanced light-sensitive device can match the contrivance of the human eye. Only a master engineer with superior intelligence could manufacture a series of interdependent light sensitive parts and reactions.”