Evolution of the Eye

[Mercedes Benzene]

One of the largest challenges to Darwin's theory of evolution is the eyeball.
The concept produces a challenging question:
-The first organisms could not possibly have known that there was anything to "see". Where could an eyeball have come from?


Some have suggested that eyes evolved from light sensitive "spots", but this itself poses some questions.
-Why would a light sensitive spot have been necessary??
-What would necessitate the need for such a spot??

Please feel free to post your ideas.

[InfiniteNow]

Eyes absolutely are the result of evolution.

Originally Posted by Mercedes Benzene

Where could an eyeball have come from?

Certain cells reacted differently to light than dark. It may even go further back and the distinction could be heat/cold. However, this would have provided some sort of advantage, been passed on to offspring, and the trait would increase in strength.

-Why would a light sensitive spot have been necessary?? -What would necessitate the need for such a spot??

Perhaps more important would be when the light spot goes away. If you're suddenly shadowed by a large predator, noticing the shadow could be quite an advantage when it comes to escaping... even on a molecular level. I don't want that phage to eat me... I'd better be able to see the difference in light as they approach so I can high-tail it out of here.

Through the years, those with the more advanced light/dark recognition systems became more dominant, spreading, and further enhancing their abilities with each generation.

[Vagabond -SC2-]

I would say evolution of the eye, yes..

Light meant food and warmth = life

So primitive organisms may have wanted to go towards light. but if light got to intense would want to avoid it.

[ughaibu]

Photosynthesis was a relatively early evolutionary development, as organisms have had a parasitic relationship with light for so long, I dont think the eye is at all surprising.

[Pyrotex]

Originally Posted by Mercedes Benzene

One of the largest challenges to Darwin's theory of evolution is the eyeball....Some have suggested that eyes evolved from light sensitive "spots", but this itself poses some questions.-Why would a light sensitive spot have been necessary??.

The answer to this vexing problem has been spelled out in fascinating and precise detail by the likes of Richard Dawkins, in his book "Climbing Mount Improbable" and Daniel Dennett (who is a philosopher) in his book "Darwin's Dangerous Idea". Both books are fun to read.

Let's take your two questions, which are really just one: Why would a light sensitive spot have been necessary? The answer is: they would NOT have been necessary.



That's right, they weren't necessary. Single cell critters lived and died like crazy without those spots. Seeing as how they were the very first critters on Earth, and the whole DNA/reproduction thing was nowhere near as "exact" and "self-correcting" as it eventually became, reproduction was not "exact". Critters were constantly bumping into new chemicals, being poisoned, eating them, absorbing them, incorporating them, creating them, excreting them. And this led to zillions of cells that were different in one way or another.

Do you know how many chemicals are sensitive to light? Lots. The entire porphyrin family are ALL light sensitive to one extent or another. A molecule gets hit with a photon of the right energy, and the molecule twitches. Or pops off an electron. Nothing fancy or complicated at all.

There would be single cell critters that could "benefit" from knowing if it was day or night. Knowing that could make them more efficient, because sunlight affects the environment drastically: temperature, tides, deep water currents raising nutrients to the surface.

All it would take would be one critter with a flummoxed RNA strand that caused it to create a single porphyrin molecule--a molecule that when "energized" by light kicked off electrons that activate the critter; and when not--the critter became dormant. (or vice versa, either). Bingo, you have a critter that "knows something" its neighbors do not. If this gives it any survival advantage at all (THE CORE OF EVOLUTION THEORY) then its descendents will tend to outnumber those critters who can't do this trick.

There really is NOTHING very hard or complicated about this. In the first billion years, Life would have been sloppy, unstable and hit-or-miss in its reproductive process, as you would expect. That means random variations out the wazoo. Mutations for a simple single cell critter do not carry the same "death penalty" as they do for large complex animals. So, trillions of these random variations would have been "experiments": does THIS increase my survivability? does THIS increase my survivability? does THIS increase my survivability?...

[InfiniteNow]

Originally Posted by Pyrotex

Bingo, you have a critter that "knows something" its neighbors do not. If this gives it any survival advantage at all (THE CORE OF EVOLUTION THEORY) then its descendents will tend to outnumber those critters who can't do this trick.

And as many of us have realized on numerous occasion, this post being no exception, we're all gonna die out, but Pyrotex and his descendants will live on.

[HappytheStripper]

Hi All ..

I havent voted .. as im looking for the pole .. not poll .. hehe lol ..

In regards to the eye of evolution have a look at this site .. go to ..

http://www.spaceclusters.org

Then once you have viewed it lemme know plz what you think .. I have been thinking about this thread though and will continue to do so .. for awhile longer then reply with my thoughts on the matter ..

Regards Ashley

[Pyrotex]

Originally Posted by HappytheStripper

...In regards to the eye of evolution have a look at this site... http://www.spaceclusters.org ...

Greetings Ashley!
I have read the website you reffed above. It is intriguing, thoughtful, interesting, novel, artistic and several other adjectives. Above all, I think, it reflects the world view of an artist, who uses his art as a metaphor for existence and reality. No harm in that. Even Picasso did that, but not as explicitly.

What does this website have to do with the evolution of the eye? Well...not much. That is to say... nothing at all. But it is interesting! Thanks!

Good luck with your pole!

[Mercedes Benzene]

Well, it seems that (according to the poll), we are all in agreement!
Does anybody have any arguements against the "evolution of the eyeball"?

[Pyrotex]

Originally Posted by Mercedes Benzene

...Does anybody have any arguements against the "evolution of the eyeball"?

moi?? au contraire!!

The current "arguement" against the eyeball goes like this: the eyeball is sooo complicated, that if even one molecule [type] is changed or one tiny cell [type] absent, then the whole thing would not work at all. Therefore there is no previous evolutionary step that the eyeball could have evolved from.

This argument is fallacious on several levels and relies primarily on "word play". There are millions of different eyeballs out there in mammals, birds, reptiles, insects, jellyfish, you name it. So obviously there ARE changes you can make in an eye that permits the eye to still function! There are in fact over two dozen distinctly different architectures for eyes--by this I mean "blueprints" for a basic eye structure that could not have evolved from each other!!!

For example, in the human retina, the nervous system attaches to the FRONT of each retinal cell, does a 180 degree "yuey", exits the retinaand then follows the rear of the retina curvature to the optic nerve. In the octopus, the nervous system attaches to the REAR of each retinal cell, and directly exits the retina. I won't give the whole argument here, but a little thought should end with the conclusion that OUR eyeball could NOT have evolved from the octopus eyeball--and vice versa. The architectures are TOO different.

Therefore, the evolutionary invention of the eye must have such a useful "trick" that it evolved independantly at least two dozen times in the first billion plus years of Life on this planet.