Why haven't we evolved eyes in the backs of our heads?

July 2, 2009, 12:00 pm by Scientific American: Health

As much as we might appreciate the value of detecting predators that approach from behind--or of keeping an eye on the offspring who follow us--it is important to remember that selection is not directed toward the development or formation of anything, let alone “perfect” organs. In other words, just because some feature seems like a good idea, random mutation and selection will not necessarily fashion it.Body parts that enable us to detect the sights, sounds, smells, tastes, temperature and tactile elements of our environment did not arise from some master plan or blueprint. Rather selection crafted body parts from available components of cells and tissues within existing forms of life, molding ancient and intermediate versions of sensory cells and organs--each elegant in its own right--like lumps of clay over aeons into the shape and form of our modern bodies. There have never been perfectly formed organs for sight or hearing--just versions that get the job done. [More]

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