How does an eye evolve?

Question

An eye must be perfect to function.

It cannot function by gaining parts overs 100's or 1000's of years.

How is it possible for an eye to evolve and if a species can go for 100's or 1000's of years without functioning eyes.. Why?

But which cells would think of adding a sense on.

Because without eyes, there is no sight, so how can such simple cells comprehend creating an uncreated sense, to do something that isn't known to even do anything.

Cells are designed. As is everything else in my opinion.

No matter the form of an eye, it has it's main function.. To see.

And before eyes had 'evolved' there was no such thing as sight.

How does a cell think of creating sight when it isn't created yet?

For that matter, how does a simple cell know how to construct an eye?

If this was the case, why does it take $10000's of dollars of research to look in to the matter with no solution on to how a cell can 'evolve' from a cell in to a human being.

How can something know there is light, if no such eye like thing is on the organism?

You can't adjust something you don't have..

And on the time it takes for 'evolution' to occur, what's to say the environment the organism is in has the same needs for eyes?

If cells 'mutate'.. How can an eye be so perfect?

It by an off chance just happened to mutate with everything in the EXACT right place to see?

If this were the case, why is the human body a perfect design for what it is designed to do?

A mutated 'human' surely wouldn't be so perfect.

Answer 1

As others have stated - Dawkins has answered this question rather well.

To answer a few of your other questions:

> But which cells would think of adding a sense on.

Cells don't "think" of anything.

> Because without eyes, there is no sight, so how can such
>simple cells comprehend creating an uncreated sense, to
>do something that isn't known to even do anything.

Think of it like this: plants have no eyes, but they can perceive light ("photoperception"). In fact, they use light to "feed".
The chemicals used in *all* organisms to perform photoperception are carotenoids. Beta-carotene is used in photosynthesis as an accessory pigment, and it is used in animal eyes as the chemical that actually detects the incoming light.
What this tells us is that the mechanism of "picking up" light evolved before animals and plants diverged: plants use it to obtain food, while animals use it to perceive light. Initially, this will just have been useful to tell light from dark (maybe it's better to be active in one or the other), will have evolved into direction-sensing (up vs down in sunlit water), and onwards to image-perception.

>No matter the form of an eye, it has it's main function.. To
>see.
>
>And before eyes had 'evolved' there was no such thing as
>sight.

Extend this to photoperception, and - as I answered above - this is patently untrue.

>How does a cell think of creating sight when it isn't created
>yet?

Cells *don't* "think"!

>For that matter, how does a simple cell know how to
>construct an eye?

Evolution doesn't work that way. There is *NO* conscious input. Organisms that are better adapted survive more often, and pass on those advantageous traits to their offspring; and that's all there is to it.

> If this was the case, why does it take $10000's of dollars of
>research to look in to the matter with no solution on to how a
>cell can 'evolve' from a cell in to a human being.

You are the one asserting there is no solution. Most biologists think that this particular riddle has been satisfactorily solved, thank you very much.

>How can something know there is light, if no such eye like
>thing is on the organism?

You don't need an eye, all you need is a photoreceptor.

>And on the time it takes for 'evolution' to occur, what's to say
>the environment the organism is in has the same needs for
>eyes?

Normally, the environment changes quite slowly - giving more than enough time to evolve. Simple, rapidly-reproducing organisms evolve very quickly: just look to the emergence of pesticide-resistant mosquitoes *within our lifetimes*.
If something makes the environment change quickly, then lots of extinctions occur. But more species evolve to "fill the gaps" after the change.
And having eyes is *such* a huge advantage, in almost any environment except lightless ones, that they are always going to be selected for.

>If cells 'mutate'.. How can an eye be so perfect?

Cumulative "improvement" mutations, adding up over time.
And FYI - our eyes are *far* from perfect. They're good, sure, but there are a number of problems with them, like our blind spot, required because the nerves for the retina are *in front* of the photoreceptors, and have to pass through in order to get to the brain. Octopus eyes, which are almost identical to vertebrate eyes, do not have this design flaw - so if our eyes were designed, why so badly?

>It by an off chance just happened to mutate with everything
>in the EXACT right place to see?

Nope. Plently of mutations would have been detrimental, but those ones were selected against, and so we don't see them nowadays.

> If this were the case, why is the human body a perfect
>design for what it is designed to do?

It's not; in fact, it is a very poor design. Our spines cannot withstand a lifetime of us being upright, so humans get lots of back-problems. Our pelvises are poorly-designed for giving birth through (and our babies' heads too big), so human birth is prolonged and difficult, and our babies have to be born too early, leaving them helpless for a long period of time.

> A mutated 'human' surely wouldn't be so perfect.

Many would not, but some would.
For every person with cystic fibrosis (a genetic mutation), there will be someone with slightly better eyesight, or better haemoglobin for exercise, or who is more intelligent, or resistant to AIDS, or something else.
mutations are either good, neutral, or bad. But we ususally only hear about the bad ones (outside of the X-men)

Answer 2

Your a moron... Does a micro organism have an eye? Not one you can see nor a brain. Does a fly have 2 eyes? well I'm sure god made a fly for some purpose... NOT. Trees and plants are living and they are still evolving.. They don't need eyes, And evolution is on a pause. When the comet hit the earth millions of years ago and wiped out the dinosaurs.. New life started to begin.. And once again when we get hit by the comet which we will it will wipe us out and new life will begin. Micro-organisms / DNA = intelligent. Dinosaurs = intelligent. Humans = not so intelligent.

Answer 3

You premise that an eye must function perfectly to function is wrong. It is easy to demonstrate that by looking at existing eyes in various species. Check out the "eyes" in organisms like Euglena.
You can also check out the website below.
Eye evolution has been satisfactorily explained. You just haven't learned it yet.

If you don't know where cells get their instructions from (genes/DNA) you clearly have no background whatsoever in biology. I would suggest that you take some biology classes before you try to argue biology subjects. You are currently indeed like a blind man trying to argue that the color of the sky is black.

Answer 4

What is the purpose of the eye? It is to sense light. Everything else is just extra function to make the job of sensing light better. So the eye started out as cells that are sensitive to light and then through random mutation it got better at its job.

Either way, go talk to your local biology professor if you really want to understand evolution. Yahoo Answer is hardly the place for it.

Answer 5

Don't start with false assumptions. Eyeless creatures did not suddenly spawn offspring with fully formed eyes as we know them today. Light sensitivity came first with gradual refinements over time.

Evolution does not think. It has no goal. Changes either enhance the survival characteristics of a species or they don't. whatever enhances survival is carried into succeeding generations and so, becomes the dominant trait.

Answer 6

Actually if you think about it a eye CAN function by gaining parts over many thousands of years. You assume that in order to be an eye the organ must be able to "see" in the same level of detail as we can now.

You incorrectly assume that the way we see the world is the only possible way to do so.Many creatures on this planet have eyes different to our own that see the world in a different way, Have a look at how we think flies see the world for instance. Dogs eyes cannot see in colour.

The idea of evolution is that mutations of something that give an advantage have a higher chance of survival. So an eye that can make out shapes is superceded by an eye that can make distinctions between shapes by colour and then one that can make out detailed textures etc. Eventually you can the complex organ that you see with today.

Edit - Cells don't "think" they mutate, that is what evolution is about.

Cut and paste, i take no credit for the following but you pricked my interest and i thought you might find this interesting as well:

The eye is a famous example of a supposedly "irreducibly complex" structure: due to its many elaborate and interlocking parts, seemingly all dependent upon one another for proper functioning, it is frequently claimed that the eye could not have evolved through gradual, step-by-step, evolutionary improvements guided only by natural selection.

Michael Behe used the "development of the eye problem" as evidence for intelligent design in his controversial book, Darwin's Black Box, and creationist website Answers in Genesis describes the eye as evolutionary biologists' "greatest challenge as an example of superb 'irreducible complexity' in God's creation".[23]

The argument that the eye could not have evolved is most commonly invoked in questions such as "What good is half an eye?" The assumption is that an incomplete eye would be completely useless for sight, and therefore an eye could never have evolved through the gradual, step-by-step progression required by modern evolutionary theory. However, this claim has been heavily disputed based on the plentiful evidence of suboptimal eyes in nature. Such eyes, despite their shortcomings, tend to be dramatically more useful for organisms than no eyes at all would be: people with visual impairments are generally much more able to function normally than people who are completely blind, and there are millions of species of animals with significantly simpler eyes than humans that nonetheless thrive, and are in many cases much more successful than similar species with still poorer vision.[21] Thus eyes with decreased functionality, in humans and in numerous other species, still tend to be more beneficial than having no eyes at all.[24]

Conversely, the human eye is suboptimal compared to what many would consider to be "lesser animals." Human visual acuity is, in daytime, noticeably less than that of raptors in terms of spatial resolution, and significantly less than various insects in terms of spectral range. At night, visual acuity is less than predators such as raptors and cats, and invertebrate molluscs such as squid and octopuses. The visual champion, however, is currently the mantis shrimp. This invertebrate possesses polarization capability, hyperspectral capability (with three to four times the number of receptors by range as humans, without including interpolation, over a wider spectral range), and triple redundant depth perception from both their eye constructions and their multiple eyestalk motions (both 2D tracking, and axial rotation). The fact that these capabilities are achieved using a compound eye layout is especially notable, and a sign of radically divergent evolution[citation needed]. Thus, the vertebrate layout can be considered half (perhaps even a third or less) of an eye compared to the mantis shrimp form, while still being "good" in many respects.

Although the eye remains a common and popular example of complexity in arguments against evolution, some intelligent design and creationism advocates have abandoned the eye as an example of "irreducible complexity". As the detail and history of eye evolution have become better understood, its role in these circles has declined and been replaced by molecular and microscopic structures such as the flagellum. However, much as with the eye, research into these smaller-scale structures has also uncovered details of their evolution[25] but these details are not linked to produce the complete process yet.

The eye argument might be said to stem from a "God of the gaps" strategy, or more broadly, the "argument from incredulity" fallacy.

Answer 7

Would you choose to be partially blind or totally blind? Clearly having part of an eye is preferable to being utterly blind.