June 12, 2007 | David F. Coppedge

Why Do Some Fruit Bats Have Color Vision?

One would think bats don’t need color, since most fly at night.  That’s what scientists thought, reported Max Planck Institute, until color-vision cones were found in some species.  Some species have two cone types, giving them bichromatic vision, and some have only one, making them effectively color blind.
    Bats come in two orders: big and small.  We usually think of the small microbats that live in caves and use echolocation, but the megabats, or flying foxes, do not use sonar.  They fly at twilight or during the day.  Both orders are amply supplied with the light-sensitive rods.
    The scientists found that some megabats have green and blue cones, but three species have only green cones.  They surmised that these species, roosting in darker quarters of caves and trees and flying only in twilight, lost the use of their blue cones.  One commented, “A loss of blue cones is a rare event in evolution, it has been found in only a few mammals.”  Otherwise, the retinas of bats are normal for mammals, not an ”evolutionary quirk,” another commented.
    This story was also reported in Science Daily.

Loss of function is not evolution.  Natural selection is able to remove useless organs, but no one has observed it evolve a new organ.  That would require the acquisition of new genetic instructions.  Think of the difficulty of adding a new blue cone, for instance, where one did not exist before.  Having all the parts of a blue cone come together by chance would be just the first improbability.  The brain would have to understand the signal, and the bat would have to know how to differentiate and use the new color.  Fruit bats are not blind as a bat, the title said – but some evolutionists are.

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Categories: Mammals

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