Although well-adapted to its purposes, to a degree consistent with evolution, the human eye is imperfect. I am no longer sure whether the inversion of the vertebrate retina is as severe a defect as I had thought before, but the fact that it produces a blind spot in the visual field of each eye where the neurons exit must be counted as an imperfection: surely an all-powerful designer whose crowning creation was man could have done better than that, whatever we think of the general efficiency of the eye.
The blind spot is, of course, not the only imperfection of the eye: it suffers from all of the normal afflictions of the human body: including vulnerability to trauma and disease, and to wear and tear. Were the eye perfectly designed, we should expect it to be more resistant to malfunction than it is. Remember, when we talk about a creator god, we are talking about a being whose power is unlimited, unconstrained even by the laws of nature themselves; had such a being wished to make our eyes out of glowing ethereal quintessence (with no blind spots), there would have been nothing to stop him. One might argue that the deficiencies of the eye, like the pain of childbirth, were the results of the Fall of Man, coming into being because of God's response to the disobedience of Adam and Eve; however, this is to acknowledge that things as we see them today are in fact imperfect, and thus undermines the claim under analysis.
Imperfect engineering is apparent in far more than the human eye, and extends beyond the vulnerabilities of flesh. Useless and inefficient structures that appear to be relics of distant ancestors abound in the natural world, such as the hollow bones of flightless birds, the clumsy "thumb" of the giant Panda, and the vestigial pelvis of pythons and whales (Futuyma 1983:198-200). If these things are the work of a creator, the creator apparently wants us to believe in evolution.
Futuyma DJ. 1983. Science on Trial: The Case for Evolution. New York: Pantheon.
Last updated: 22 Nov 2014
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