Evolution of The Eye - History of Research

History of Research

The complex structure of the eye has been used as evidence to support the theory that they have been designed by a creator, as it has been said to be unlikely to have evolved via natural selection. In 1802, philosopher William Paley called it a miracle of "design". Charles Darwin himself wrote in his Origin of Species, that the evolution of the eye by natural selection at first glance seemed "absurd in the highest possible degree". However, he went on to explain that despite the difficulty in imagining it, this was perfectly feasible:

...if numerous gradations from a perfect and complex eye to one very imperfect and simple, each grade being useful to its possessor, can be shown to exist; if further, the eye does vary ever so slightly, and the variations be inherited, which is certainly the case; and if any variation or modification in the organ be ever useful to an 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, can hardly be considered real.

He suggested a gradation from "an optic nerve merely coated with pigment, and without any other mechanism" to "a moderately high stage of perfection", giving examples of ‹See Tfd›extant intermediate grades of evolution. Darwin's suggestions were soon shown to be correct, and current research is investigating the genetic mechanisms responsible for eye development and evolution.