Evolution of the Eye

Fundamentalist Creationists argue: “Something as complicated as an eye must have been designed and/or made by a super-intelligent Creator.” (This creationist argument is sometimes called “The Argument of Irreducible Complexity.”)

We Participants in Nature’s Continuing Creation respond:  In fact, “The eye evolved from a single, light sensitive spot in a cell into the complex eye of today not by chance, but through thousands of intermediate steps, each preserved because they made a better eye. Many of these steps still exist in nature in simpler organisms.” (See Skeptics Society, “Top 10 Myths About Evolution.”)

“Darwin suggested that even ‘incomplete’ eyes might confer benefits (such as helping creatures orient toward light) and thereby survive for further evolutionary refinement. Biology has vindicated Darwin: researchers have identified primitive eyes and light-sensing organs throughout the animal kingdom and have even tracked the evolutionary history of eyes through comparative genetics. It now appears that in various families of organisms, eyes have evolved independently.” (See John Rennie, “15 Answers to Creationist Nonsense,” Scientific American, 7-1-2002)

Biologist Richard Dawkins gives us a more complete counter argument in his book, The Blind Watchmaker.  In fact, there are many creatures out there today which have and make use of very primitive “eyes.” Dr. Dawkins writes, “Some single-celled animals have a light sensitive spot with a little pigment screen behind it. The screen shields it from light coming from one direction, which gives it some ‘idea’ of where the light is coming from.  Among many-celled animals, various types of worms and some shellfish have a similar arrangement, but the pigment-backed light-sensitive cells are set in a little cup. This gives slightly better direction-finding capability…

“… Now, if you make a cup very deep and turn the sides over, you eventually make a lens-less pinhole camera…The swimming mollusk nautilus… has a pair of pinhole cameras for eyes… When you have a cup for an eye, almost any vaguely convex, vaguely transparent or even translucent material over its opening will constitute an improvement, because of its slight lens-like properties.”  Alternatives to eyes have also evolved.  “For instance, the curved dish-reflector principle (we use it in radio-telescopes) has been independently ‘invented’ by various mollusks and crustaceans.  Other crustaceans have a compound eye like insects — actually, it’s a bank of lots of tiny eyes.”  (See Richard Dawkins, The Blind Watchmaker.)

We must also point out that the eye is actually poorly “designed.” The sense of sight involves too many steps, too many organ structures in the eye and brain, too many translations from light to chemical reactions, to electrical signals. This “Rube Goldberg” apparatus shows that the eye was put together out of whatever biological parts were at hand at each step of the eye’s evolution, over a very long span of time. (See, Skeptics Society, Top 10 Myths About Evolution.)

Nature is full of creatures with inefficient features. For example, humans, like all mammals, breathe and eat through the same tube, making it easy to choke to death. Also, the laryngeal nerve descends below the larynx, loops around an artery in the chest, and then goes back up to the larynx.  As Professor Dawkins points out, “This setup is not very efficient, especially if you are a giraffe!” 

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