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Claim CB301:

The eye is too complex to have evolved.


Hitching, Francis, 1982. The Neck of the Giraffe, New York: Meridian, pp. 66-68.


  1. This is the quintessential example of the argument from incredulity. The source making the claim usually quotes Darwin saying that the evolution of the eye seems "absurd in the highest degree". However, Darwin follows that statement with a three-and-a-half-page proposal of intermediate stages through which eyes might have evolved via gradual steps (Darwin 1872).


    Evidence for one step in the evolution of the vertebrate eye comes from comparative anatomy and genetics. The vertebrate βγ-crystallin genes, which code for several proteins crucial for the lens, are very similar to the Ciona βγ-crystallin gene. Ciona is an urochordate, a distant relative of vertebrates. Ciona's single βγ-crystallin gene is expressed in its otolith, a pigmented sister cell of the light-sensing ocellus. The origin of the lens appears to be based on co-optation of previously existing elements in a lensless system.



Lindsay, Don, 1998. How long would the fish eye take to evolve?


  1. Darwin, C., 1872. The Origin of Species, 1st Edition. Senate, London, chpt. 6,
  2. Nilsson, D.-E. and S. Pelger, 1994. A pessimistic estimate of the time required for an eye to evolve. Proceedings of the Royal Society of London, Biological Sciences, 256: 53-58.

  3. Shimeld, Sebastian M. et al. 2005. Urochordate βγ-crystallin and the evolutionary origin of the vertebrate eye lens. Current Biology 15: 1684-1689.

Further Reading:

Dawkins, Richard, 1996. Climbing Mount Improbable, New York: W.W. Norton, chpt. 5.

Land, M. F. and D.-E. Nilsson, 2002. Animal Eyes. Oxford University Press.

Fernald, Russell D. 2006. Casting a genetic light on the evolution of eyes. Science 313: 1914-1918.

created 2001-2-17, modified 2007-11-10