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Index to Creationist Claims,  edited by Mark Isaak,    Copyright © 2005
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Claim CB751:

If one eye mutates into existence, then the animal would have just one eye, not two. The same goes for arms, feet, ears, wings, and so forth. Evolution says these body parts should arise one at a time, yet most animals have bilateral symmetry. We do not find one-flippered dolphins or one-eared ape-men.

Source:

Pinkoski, Jim. 1993. A Creationist's View of Dinosaurs and the Theory of Evolution. Amazing Facts, Inc., Roseville, CA.

Response:

  1. Eyes, legs, and all the rest are not evolved anew in each animal. Bilateral symmetry evolved more than five hundred million years ago. Animals since then have inherited that symmetry.

  2. Bilateral symmetry is implemented by signalling molecules that give identical domains on left and right. A person's left eye (normally) is exposed to the same development signals as their right eye, so the two eyes grow alike. A single mutation that varies how an eye develops would still affect both eyes equally. For asymmetrical eyes, an additional mechanism must evolve to supercede the symmetry and give different development signals to each side.

Links:

Myers, P. Z. 2005 (12 June). Pinkoski again: How stupid can creationism get? http://pharyngula.org/index/weblog/comments/pinkoski_again/

Further Reading:

Carroll, Sean B. 2005. Endless Forms Most Beautiful. New York: W. W. Norton.
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created 2005-6-18