Late_Cretaceous

We have all seen the image of "what a fly sees", multiple images of the same thing based on the fact that they have compound eyes. This popular image, however is incorrect. The compound lenses of a fly's eye can focus multiple images of a particular scene on photgraphic paper which can be developed (I remember seeing one that had images of a church steeple), hence the idea that "this is what a fly sees". Our own eye lens works in the same way, so does a magnifying glass (hold a magnifying glass up to a wall directly opposite a window and, with some adjustment an image of what is outside thje window will be projected onto the wall). Using the magnifying glass demonstration, you will see that the image is only in focus at one particular distance - the focal length The problem is that for the images to be in focus, the lenses from the fly's eye must be held several inches from the photgraphic paper. A focal length of several inches in a creature less then one inch long. The fly's retina is directly behing the lens (ulike our own where the retina is at a distance equal to the focal lenght of the lens) and therefore a focused image is impossible. The fly's view of the world is more likely a single image deivded into hexagonal segments - not nearly as clear as what a single lense eye can produce if the focal lenth of that lens is emplyed. So, a fly (and most other insects) have perfectly funtional lenses in them which they don't really use.

So, what the heck does that have to do with evolution? Well, it is an example of how evolution can produce structures with unintended or unexploited potential. If organisms have structures with unexploited potential, then certain mutations may occur which are able to take advantage of them. Then you can see how a clam's gill may come to used as a luer for fish, for example.

Mageth

Not to mention that it kinda shoots a hole in "intelligent design."