[berned]

I would like a pro-evolutionist to explan briefly how either of the following complex systems could have evolved:

1. The human eye

What an excellent question! The eye has a lens to focus light. a retina, a cornea, the eyeball itself, and the "wiring" back to the brain. Did the wiring "evolve" before the eyeball? If so, what would impell the organism to "design" wiring if nothing was attached to it?

If the eyeball came first, how did the organism get the necessary feedback to know if the eyeball design was best, without the wiring back to the brain?

Furthermore, without the eye having ALL the necessary components (say it had a lens but no retina, or a cornea but no lens, etc) then how could it get the necessary design feedback to even START the design?

[Raymond Hendrix]

Yea but it could have, would have and may have happened anyway. And besides where is you imagination??? With evolution all things are possible if you only believe. Just make up a good story and you can call it science!

[The Mike Device]

You ask these questions as if Homo sapiens were the only living organism to ever have an eye or light sensitive organ of any kind. You can't really have that simplistic a world view can you?

[Junior]

The whole gamut of eyes exists, from simple light-sensitive spots on the skin (which humans retain, by the way) all the way up through the wonders of nature sported by eagles. Every step in the development of the eye is still represented by extent creatures. The eye was one of the very first of the "irreducible complexity" arguments to fall -- Darwin, himself, showed the steps in the evolution of the eye.

[Physicist]

The eye has a lens to focus light. a retina, a cornea, the eyeball itself, and the "wiring" back to the brain. Did the wiring "evolve" before the eyeball?

Yes.

If so, what would impell the organism to "design" wiring if nothing was attached to it?

Will you stipulate to the fact that organisms need a nervous system, even if they don't have eyes?

If some external nerve endings gained, through mutation, the ability to react to light, it would be useful, wouldn't it? Such a creature could tell day from night, for example, or seek shade.

Furthermore, without the eye having ALL the necessary components (say it had a lens but no retina, or a cornea but no lens, etc) then how could it get the necessary design feedback to even START the design?

Some lower animals just have a retina, in the form of photosensitive patches on their heads.

If a photosensitive patch gained any concavity, again through a slight mutation, it would be more useful. A crude sense of directionality would result. The more curved is the retina, the better the sense of directionality. By imperceptible degrees, evolution would mold the retina into a sphere with a tiny opening. Such a pinhole camera gives excellent focus at any distance.

But still it can be better. If the muscle around the opening could flex in certain ways, the aperture could be changed, trading off focus for light gathering ability. A small mutation thus gives you a functional iris. The chambered nautilus has such an eye.

But this eye can be better. A membrane would be useful to keep out vermin (another small mutation). A fluid with a higher index of refraction would be useful, too: another small mutation gives the vitreous humor.

Finally, a thickening of the membrane by a small mutation gives a functional lens, which permits a much wider aperture while maintaining focus. This is the last essential component needed for a complex eye, evolved continuously by imperceptible degrees with functional improvement at every generation.

[RonF]

Try studying comparative anatomy. Eye structures run the gamut from the mamallian eye (many of which are better than ours), down to simple single light-sensing cells. Follow the path for clues to the evolutionary trail. There's lots of light-sensitive structures that have nowhere near the features of human eyes, but still can sense light and give an evolutionary advantage to their owner.