The Evolution of the Eye

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Evolution sceptics often attack Darwin's theory by using the human eye as an example. How could something so complex have developed through random mutations and natural selection? How could evolution led to the creation of such a complex organ as the human eye? How could all the separate parts of the eye: the pupil, the lens, the retina, the iris, the rods and cones etc. have evolved? It was a lecture given many years ago by Richard Dawkins - explaining how the eye could have evolved on numerous occasions - that convinced me how natural selection and adaptation could explain how complex organisms had evolved on earth. He explained step by step how the first eye-like structure could have evolved into a more complex organ. Like many Biologists today, he used the range of less complex light sensitive structures that exist in living species to hypothesize the various evolutionary stages eyes may have gone through. I found this useful explanation below: “A simple light-sensitive spot on the skin of some ancestral creature gave it some tiny survival advantage, perhaps allowing it to evade a predator. Random changes then created a depression in the light-sensitive patch, a deepening pit that made "vision" a little sharper. At the same time, the pit's opening gradually narrowed, so light entered through a small aperture, like a pinhole camera. Every change had to confer a survival advantage, no matter how slight. Eventually, the light-sensitive spot evolved into a retina, the layer of cells and pigment at the back of the human eye. Over time a lens formed at the front of the eye. It could have arisen as a double-layered transparent tissue containing increasing amounts of liquid that gave it the convex curvature of the human eye.” http://www.pbs.org/wgbh/evolution/library/01/1/l_011_01.html As the article points out "eyes corresponding to every stage in this sequence have been found in existing living species. The existence of this range of less complex light-sensitive structures supports scientists' hypotheses about how complex eyes like ours could evolve." According to some calculations, an eye-like structure similar to the human eye could have evolved from a light-sensitive patch in less than 400,000. This means that the eye could have evolved separately in many species on many occasions. Amazing! What amazes you about the evolution of life on Earth?