BY Sean D. Pitman M.D.
ORIGINAL ARTICLE: http://www.detectingdesign.com/humaneye.html
No discussion of evolution seems complete without bringing up the topic of the human eye. Despite its deceptively simple anatomical appearance, the human eye is an incredibly complicated structure. Even in this age of great scientific learning and understanding, the full complexity of the human eye has yet to be fully understood. It seems that with increased learning comes increased amazement in that the complexity that once seemed approachable continues to be just as incomprehensible as ever, if not more so. It is well documented that Darwin stood in wonder at the complexity of the eye, even from what little he knew of it in comparison to modern science. And yet, though he could not explain exactly how, he believed that such amazing complexity could be developed through a naturalistic process of evolution. Very small changes, selected as advantageous, could be passed on and multiplied over many generations to produce major miracles of complexity such as the human eye.
Numerous Gradations
Obviously, Darwin was not crazy. His proposed theory of evolution and his basic explanations concerning the gradual development of complex structures, such as the eye, have convinced the vast majority of modern scientists. So, what exactly did he propose to explain the complexity of such structures as the human eye? Consider the following quote from Darwin.
Reason tells me, that if numerous gradations from a simple and imperfect eye to one complex and perfect can be shown to exist, each grade being useful to its possessor, as is certainly the case; if further, the eye ever varies and the variations be inherited, as is likewise certainly the case and if such variations should be useful to any animal under changing conditions of life, then the difficulty of believing that a perfect and complex eye could be formed by natural selection, though insuperable by our imagination, should not be considered as subversive of the theory.1
Darwin was at a loss to explain exactly what was happening, but he proposed a stepwise evolution of the human eye by showing examples of differences in the eyes of other creatures that seemed to be less complex. These differences were ordered in a stepwise fashion of progression from the most simple of eyes to the most complex. There did in fact appear to be a good number of intermediaries that linked one type of eye to another type in an evolutionary pattern. Some of the most "simple"Â eyes are nothing more than spots of a small number of light sensitive cells clustered together. This type of eye is only good for sensing light from dark. It cannot detect an image. From this simple eye, Darwin proceeded to demonstrate creatures with successively more and more complex eyes till the level of the complexity of the human eye was achieved.
This scenario certainly seems reasonable. However, many theories that initially seem reasonable on paper are later disproved. Such theories need direct experimental evidence to support them before they are accepted outright as "scientific". Do complex structures such as eyes actually evolve in real life? As far as I could find, there is no documented evidence of anyone evolving an eye or even an eye spot through any sort of selection mechanism in any creature that did not have an eye before. Also, I have not seen documented evidence for the evolution of one type of eye into a different type of eye in any creature. As far as I can tell, no such evolution has ever been directly observed. Of course the argument is that such evolution takes thousands or even millions of years to occur. Maybe so, but without the ability for direct observation and testing, such assumptions, however reasonable, must maintain a higher degree of faith.
A Closer Look
The necessary faith in such a scenario increases even more when one considers the fact that even 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. In other words, for the miracle of vision to occur, even for a light sensitive spot, a great many different proteins and systems would have to evolve simultaneously, because without them all there at once, vision would not occur. For example, 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. 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.2
ORIGINAL ARTICLE: http://www.detectingdesign.com/humaneye.html
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