We have two eyes! Why?

[Samurai]

It's maybe because eukaryotic bodies tend to gravitate toward bilateral symmetry. But thats not an answer. If we evolved, some creature must have had one eye one day, right? But we don't know that for sure... Do we? There is no one creature that we know of that had one eye! When did eyes start to appear anyway? Some stage between bacteria and fishes? I really would like to get some answers on this.
And please, no "God Created Us This Way" answers!

[LowellGuy]

Why do spiders have 8 eyes? Why do some animals have compound eyes, as though the retina were on the outside, while others have humorous eyes, with the retina at the back of a fluid-filled orb? why do some fish have the ability to blink and others don't? Why are my eyes blue? Why are our optic nerves at the back of the eye where light would be best focused, instead of out of the way? Why are our optic centers in the very back of the brain instead of closer to where the eyes are, creating long, precarious nerve bundles that have to go all the way to the back of the head?

[just an allusion]

Symmetrical spatial comprehension.

[Gillette]

Evolution does not explain "Why."

Why suggests purpose or pre-design. The process of evolution has not

Two eyes (on some species) is simply what evolved, and it's good enough to get us by and keep us reproducing and maintaining the species.

[just an allusion]

EDIT: "Symmetrical spatial comprehension"...and depth perception.

[AKSamurai]

But there has got to be a creature that had on eye before it evolved to have two! Thats my point. Am I wrong?

[Divine Alien]

Some humans have one eye too. It's coz they are blind on the other eye.

[Darwins Stepchild]

AKSamurai wrote:

But there has got to be a creature that had on eye before it evolved to have two! Thats my point. Am I wrong?

Yes, you are wrong, at least your concept is wrong...that there was a one eyed creature that evolved into a two eyed creature.

[AKSamurai]

Darwins Stepchild wrote:

<quoted text>
Yes, you are wrong, at least your concept is wrong...that there was a one eyed creature that evolved into a two eyed creature.

But maybe that's what really happened?

[Darwins Stepchild]

AKSamurai wrote:

<quoted text>
But maybe that's what really happened?

Very, very doubtful.

The first human ancestor that developed eyes already had bilateral symmetry. For the most part, if something developed on the right side, a corresponding structure developed on the left. That creature would have almost certainly developed two eyespots, right and left.

[Nuggin]

AKSamurai wrote:

<quoted text>
But maybe that's what really happened?

Extremely unlikely.

Eyes evolved from light sensing skin patches. If you google eye evolution, you'll see the many stages between a patch that tells you "Light yes" or "light no" and what we now know of as the eye.

At ANY stage between light patch and modern eye, having more than one source of info gives significantly more information.

Two light sense patches tells you "light yes left" or "light no right". That's a HUGE difference.

What absolutely did NOT happen was a single light patch evolving all the way to a fully modern eye and then splitting into two.

[LowellGuy]

AKSamurai wrote:

But there has got to be a creature that had on eye before it evolved to have two! Thats my point. Am I wrong?

Why would there have had to be one eye before two? Would there have had to be a human with one eye before humans ended up with two eyes? Would three have had to be a maple tree with slightly fewer points on its leaves before maple trees ended up with leaves with as many points as they have?

[LowellGuy]

AKSamurai wrote:

<quoted text>
But maybe that's what really happened?

And maybe the first life came out of a volcano. We can "maybe" all day long, but that doesn't answer any questions.

[Erasmus05]

LowellGuy wrote:

<quoted text>
Why would there have had to be one eye before two? Would there have had to be a human with one eye before humans ended up with two eyes? Would three have had to be a maple tree with slightly fewer points on its leaves before maple trees ended up with leaves with as many points as they have?

Just for laughs ...

Perhaps creationists should argue that it is impossible for tetrapods to have evolved because at the one leg stage the animal would just go around in circles.

[AKSamurai]

I'm still convinced that one creature had only one... and I don't mean it has to be a complete eye organ as we know it. The very first formation or molecule of it, or that light skin patch. It was one! Then it divided into two, and started evolving.

[MikeF]

Erasmus05 wrote:

<quoted text>
Just for laughs ...
Perhaps creationists should argue that it is impossible for tetrapods to have evolved because at the one leg stage the animal would just go around in circles.

Wouldn't that be just another circular argument?

[Erasmus05]

MikeF wrote:

<quoted text>
Wouldn't that be just another circular argument?

Perhaps, but it does have a leg to stand on. ;)

[Erasmus05]

AKSamurai wrote:

I'm still convinced that one creature had only one...

It was one eye, one eye on each side of the bilaterally symmetrical organism.

To help drive this home, scientists have messed around with hox genes in fruitf lies. When they change one of the hox genes the fruit flies grow eyes on their legs. The important part is that they grow eyes on the same leg on each side.

http://www.bio.davidson.edu/Courses/molbio/re...

The genes that produce bilateral symmetry predate the evolution of the eye.

[LowellGuy]

AKSamurai wrote:

I'm still convinced that one creature had only one... and I don't mean it has to be a complete eye organ as we know it. The very first formation or molecule of it, or that light skin patch. It was one! Then it divided into two, and started evolving.

Evidence?

I'm convinced that you've got antlers growing from your head. I'm just convinced of it! I'm sure I'm right.

I don't need to provide any evidence. Can't you see I just said I'm convinced?

You do realize, don't you, that you've convinced yourself that you're right by telling yourself you're right without having seen datum one that supports your hypothesis, right? I mean, only the stupidest person would just throw out ideas and claim them to be true without any understanding of the subject and without any evidence to back it up.

So, do you have antlers growing out of your head? Does my claim have ANY weight just because I said I was convinced? That's exactly as much weight as your argument carries, and that's exactly why.

[Darwins Stepchild]

LowellGuy wrote:

<quoted text>
Evidence?
I'm convinced that you've got antlers growing from your head. I'm just convinced of it! I'm sure I'm right.
I don't need to provide any evidence. Can't you see I just said I'm convinced?
You do realize, don't you, that you've convinced yourself that you're right by telling yourself you're right without having seen datum one that supports your hypothesis, right? I mean, only the stupidest person would just throw out ideas and claim them to be true without any understanding of the subject and without any evidence to back it up.
So, do you have antlers growing out of your head? Does my claim have ANY weight just because I said I was convinced? That's exactly as much weight as your argument carries, and that's exactly why.

That is exactly the type of thing the scientific method is designed to eliminate...personal bias.

By requiring repeatability in observations, the bias that one or even several scientists may have is eliminated since someone is going to come up with different, unbiased results.

Part of the reason for peer review is to check the methodology of the researchers, to see if they have used proper protocols that eliminate personal bias as much as possible.