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How did eyes evolve?

My biology teacher never answered: since the eye relies on many parts to work (including contact to the brain) wouldn’t the parts clutter the path of evolution before they were all there? Also, why do more primitive life forms have more efficient eyes than man? (Teacher
Edmund Ward from North Yorkshire (Age 45-54)

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2 Responses

  1. There is a good chain of evolution of eyes from light sensing cells beneath the skin to more complex structures, although eyes are soft so fossils are not very common. If you are interested in this it should not be too difficult to find, but it is a bit long for an answer here.

    Primitive life forms do not have more efficient eyes as far as I know. Our eyes have evolved to see ripe and unripe fruit and to hunt in different environments. For this reason we have sacrificed seeing in the dark quite so well to see better in the colours that are important to us. We have sacrificed wide angle lenses that rabbits and horses have so that we can focus on smaller things to hunt and climb more effectively, but we do not have super range vison of eagles because it is also good for us to be able to see all round in case a lion is coming. Improving something about your eyes would mean making them worse at something else or make them bigger, which would make them more vulnerable to damage.

    The only clear advantage that some animals have is a third eyelid (nictating membrane), which is pretty much transparent so that they can protect their eyes against dust but still see. Cats and reptiles have them, us monkeys have to do without.

  2. If you would like to know more about this, I recommend ‘Climbing Mount Improbable’ or ‘The Ancestor’s Tale’ both by Richard Dawkins.

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