About the eyes I know that it requires for gauging distance as in Modern 3D cameras have two sensors. And two ears for sound source localization using differences in levels and timing (But not yet two microphones in mobile phones/other devices). What about other organs? Even not all organs are in pair. If it is about about redundancy then why not more than two? Thanks for your answer.
closed as off topic by Manishearth♦, Qmechanic♦, David Z♦ May 24 '12 at 7:41
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This isn't a physics question.
Bilateral symmetry in organisms is (probably) an accident of evolution dating back 500 million years or so. Humans are just one example of a very large number of bilaterally symmetric species. There's obviously an evolutionary advantage to bilateral symmetry, but there are still billions of jellyfish, starfish, sea urchins, etc out there so bilateral symmetry isn't the only route to evolutionary success.
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