Evolution of the eye
Many scientists have found the evolution of the eye attractive to study because the eye distinctively exemplifies an analogous organ found in many animal forms. Simple light detection is found in bacteria, single-celled organisms, plants and animals. Complex, image-forming eyes have evolved independently several times. Diverse eyes are known from the Burgess shale of the Middle Cambrian, and from the slightly older Emu Bay Shale. Eyes vary in their visual acuity, the range of wavelengths they can detect, their sensitivity in no light, their ability to detect motion or to resolve objects, and whether they can discriminate colours. History of research In 1802, philosopher William Paley called it a miracle of "design." In 1859, Charles Darwin himself wrote in his Origin of Species, that the evolution of the eye by natural selection seemed at first glance "absurd in the highest possible degree". However, he went on that despite the difficulty in imagining it, its evolution was perfectly feasible: ... if numerous gradations from a simple and imperfect eye to one complex and perfect can be shown to exist, each grade being useful to its possessor, as is certainly the case; if further, the eye ever varies and the variations be