Parsimonious repetition of design elements throughout creation, e.g. the eye's appearance in remarkably different species. For such complex structures to arise repeatedly via evolution is impossible, as evolution is an inherently random and historically contingent process.[3]
Not all eyes are exactly the same, thus not an example of parsimony. That eyes became a feature in many species shows their usefulness. In fact, photoreception is an ancient trait found in the very early common ancestors, which does relate to parsimony. From a simple light receptor, different organisms have developed compound eyes, camera eyes, slit eyes, etc. More closely related organisms have much more similar eyes than less similar species. All mammals share a similar anatomy of the eye, while different species have a few unique adaptations- for instance monkeys and apes have tri-color vision while other mammals do not.
The benefits of sensing the environment make eyes a very important and useful adaptation. You can imagine an ancient paramecium population. The ability to sense the light around you can provide almost instant benefit. Or a look at animals and being able to see the movements of predators can help you protect yourself. In any situation, photoreception dramatically increases your chances of survival.
Except when it doesn't. Cave dwelling animals have lost the need to see in their environments and no longer use their vestigial eyes. They still grow eyes during their development, but do not use them for any purpose of survival. That these cave dwellers retain their eyes shows their common descent from ancestors in a lighted environment.
For more on the evolution of eyes, check out this Nova video from the PBS Evolution series.
The eye demonstrates the remarkable power of evolution through natural selection.
The benefits of sensing the environment make eyes a very important and useful adaptation. You can imagine an ancient paramecium population. The ability to sense the light around you can provide almost instant benefit. Or a look at animals and being able to see the movements of predators can help you protect yourself. In any situation, photoreception dramatically increases your chances of survival.
Except when it doesn't. Cave dwelling animals have lost the need to see in their environments and no longer use their vestigial eyes. They still grow eyes during their development, but do not use them for any purpose of survival. That these cave dwellers retain their eyes shows their common descent from ancestors in a lighted environment.
For more on the evolution of eyes, check out this Nova video from the PBS Evolution series.
The eye demonstrates the remarkable power of evolution through natural selection.
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