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The evolution of the eye has been a subject of significant study, as a distinctive example of an analogous organ present in a wide variety of taxa. Complex, image-forming eyes evolved independently some 50 to 100 times.〔Land, M.F. and Nilsson, D.-E., ''Animal Eyes'', Oxford University Press, Oxford (2002).〕 Complex eyes appear to have first evolved within a few million years, in the rapid burst of evolution known as the Cambrian explosion. There is no evidence of eyes before the Cambrian, but a wide range of diversity is evident in the Middle Cambrian Burgess shale, and the slightly older Emu Bay Shale.〔Lee M.S.Y., Jago, J.B., Garcia-Bellido, D.C., Edgecombe, G.E., Gehling, J.G, Paterson, J.R. 2011. Modern optics in exceptionally preserved eyes of Early Cambrian arthropods from Australia. Nature 474: 631-634〕 Eyes show a wide range of adaptations to meet the requirements of the organisms which bear them. Eyes vary in their visual acuity, the range of wavelengths they can detect, their sensitivity in low light levels, their ability to detect motion or resolve objects, and whether they can discriminate colours. == History of research == 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 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 inherited, as is likewise certainly the case and if such variations should be useful to any animal under changing conditions of life, then the difficulty of believing that a perfect and complex eye could be formed by natural selection, 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 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. Modern researchers have been putting forth work on the topic. D.E. Nilsson has independently put forth four theorized general stages in the evolution of a vertebrate eye from a patch of photoreceptors.〔Nilsson, D.-E. 2013. Eye evolution and its functional basis. Visual Neuroscience 30:5-20〕 Nilsson and S. Pelger published a classical paper theorizing how many generations are needed to evolve a complex eye in vertebrates.〔Nilsson, D.-E., and S. Pelger. 1994. A pessimistic estimate of the time required for an eye to evolve. Proceedings of the Royal Society B: Biological Sciences 256:53-58〕 Another researcher, G.C. Young, has used fossil evidence to infer evolutionary conclusions, based on the structure of eye orbits and openings in fossilized skulls for blood vessels and nerves to go through.〔Young, G. C. 2008. Early evolution of the vertebrate eye – fossil evidence. Evo Edu Outreach 1:427-438〕 All this evidence adds to the growing amount of evidence that supports Darwin's theory. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「evolution of the eye」の詳細全文を読む スポンサード リンク
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