Did Eyelids Evolve?

Earlier forms of life (fish, insects, etc) did not (and their modern versions still do not) have eyelids. We also have examples of intermediate forms (you could call them "partial eyelids") like the previously mentioned nictating membranes found in reptiles.But the real problem with your question wasn't that you narrowed it down specifically to humans. The problem is this part here: There are several problems with your understanding of evolution demonstrated by this question, and it's these misunderstandings that are likely the cause of your confusion.There is no "EVO-Code." It's a nonsense term. Its presence in your question implies that you believe that some intelligent factor somehow "told" organisms at a certain point in history to start growing eyelids. This is not even remotely close to the way evolution works. Evolution works primarily through very small random mutations that change incredibly minute things about an organism. A mutation will not, for example, cause an organism to spontaneously sprout an arm when the parent didn't have arms. Neither will it cause the sudden appearance of eyelids. The changes are much smaller than that. The reason the process takes thousands or millions of years to produce drastic changes is the same reason it takes you a very long time to walk from New York to Arizona - where you started from doesn't much look like where you wound up, but each individual step wasn't that much different from the step before it.Mutations can be beneficial, or negative, or simply neutral. Most mutations are neutral, and don't really do anything at all individually.But the beneficial mutations (like say, a slightly longer beak that is beneficial for pecking insects out of a tree, or a thin membrane over the eyes that adds just a tiny bit of protection) give an advantage to the organisms that posess them. Specifically, the bird that can get to food even a little easier is more likely to survive long enough to produce offspring to inherit the same positive mutation over a cold winter when food might be scarce. The creature with a membrane over its eyes may be less likely to go blind (and thus more liekly to survive long enough to procreate and pass on its mutation to its offspring) in a dusty environment. As the small population with positive mutations continues to out-reproduce those who don't have such advantages, over a very long time the changes can spread out to form the majority of the population. Further mutations add up to make more drastic changes from the older ancestor (just like that long walk from New York to Arizona - all those small steps add up).The process isn't guided. There is no "instruction," or even a "suggestion" that something like an eyelid may help. It's random, and small, but even the smallest advantage helps, and the tiny changes add up to very large ones after many generations.We see the process work most easily in organisms that reproduce quickly, because even with our short lifespans, we can observe hundreds of generations in a very short time - like bacteria, or fruit flies. Bacteria who have a very small mutation that changes just a single protein in their cell membrane can become extremely resistant to antibiotics. When exposed to antibiotics, the bacteria without the mutation all die off...while the resistant one lives on and continues to reproduce. From then on, all of the surviving bacteria in that population are not resistant to antibiotics. See how the random process of tiny changes can actually change the entire population?This is how evolution works - through mutation (tiny changes in each generation) guided by natural selection (the creatures with an advantage are more likely to have offspring and pass the advantage on). Not with some strange "code" "telling" organisms to form a new appendage.You could say that the genetic code "tells" an organism how to form, but not in the way you seem to mean. DNA is literally just chemistry. The specific chemical makeup of a DNA strand will cause different proteins to be formed (this is simplified, but hopefully should help you understand), which is what causes those tiny changes we call mutations. The copying process for DNA is imperfect, which is what allows the small changes to pass through instead of making exact duplicates for every generation. But it's literally a random process of imperfect copying, much like making a typo - there is no intelligence guiding the process, there is no decision or suggestion or instruction involved. The DNA strand copies with a small change because the chemical bonds work just as well with one base pair as with another. It's like legos - there are a limited number of peices, but they all fit together just fine. In DNA, the order of the peices is what determines the proteins and thus the expression in the organism, so even though the peices are basically mix and match, the small changes made with imperfect copying let small changes be made in the way the organism works. A single mutation may change the color of your eyes (I'm not positive - even something as tiny as that may be affected by multiple genes, but it's a good example), or many mutations over thousands of generations could change something significant, like certain primates having shorter and shorter tails, until eventually some of their descentants (that would be us) don't have tails at all.That was a hell of a long post...but does this answer your question, and maybe clear up some misconceptions about evolution? It's a lot more complicated than they teach you in High School, and 100% different from what AnswersinGenesis or your local pastor are likely to tell you, so don't worry - most people don't know what the real Theory of Evolution is, either.

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Every time a fundy breaks the laws of thermodynamics, Schroedinger probably kills his cat.

I know. But the way you used the term indicates you are working under the assumption that an organism must be "told" to produce a feature. That is not the case. Incredulity is irrelevant. We have seen all of this happen. No, not every step of the formation of every species - but we have observed mutation, tracked the traits to the genetic code, and further examined the DNA copying sequence and seen exactly how the altered trait was changed. You say it doesn't compute - but we have actually observed this in real organisms. We have even observed actual new species arise from existing species, in the laboratory. We know from direct observation that mutation and natural selection do produce changes in species populations over time. It's not a matter of belief - you can do the same experiments and observe it yourself.That's the point of science, after all. Cosmetic changes are the same as all other changes, simple (sometimes) on a smaller scale.The human reproductive system is basically identical to the reproductive system of all mammals, with really only cosmetic differences. But let's not shift the topic, shall we? The topic here is the evolution of eyelids. You're welcome to start another thread, but really - it's the exact same process. Eyelids work just fine as an example of an evolved trait, just as human reproduction would be. We have examples of other reproductive systems (eggs, seeds, budding, mitosis, etc) just as we have examples of other eye protection - nictating membranes, the ability to withdraw the eyes, etc.Reproduction has certainly been evolving for longer than there were eyes to protect...think of it as walking only to Indiana from New York instead of all the way to Arizona...but the process is identical. Don't take it personally. We literally repeat the same answers to the same misconceptions (and sometimes misrepresentations) around here every time a new Creationist member joins. Remember how I said AnswersinGenesis puts forward a completely false version of evolution? Many of us just get frustrated, and are irritated by repeating the same refutation of the same simple misconception for the 1746th time.

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Every time a fundy breaks the laws of thermodynamics, Schroedinger probably kills his cat.

I don't require your babying. This is a debate forum. If you find my explanation unconvincing, please explain and rebut. Then this isn't the place for you. This is a debate forum. To remain here without being suspended, you will be required to participate in debate. If you're here to "get a rise out of the evolutionists," you'll be suspended pretty quickly. We'll be more than happy to show you what the actual Theory of Evolution states, and how the process it describes works, to the best of our ability. But please, if you find something unconvincing, or dont understand something we say, say so. That way you participate in the debate, and we can be sure that, whether you accept it or not, by the time you're done here you at least understand what it is you're arguing against. It's more like "changing the subject." Let's stick with the actual topic of the thread, shall we? I mean, you say you're still unconvinced - specifically, why? What do you not understand, or find convincing?

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Every time a fundy breaks the laws of thermodynamics, Schroedinger probably kills his cat.

That's good. Because it's not completely random. Chemistry works only in very specific ways. The genetic code is wildly variable, but at its essence is only composed of a very few base pairs.I know this is branching from the topic a bit, but I'll run with it anyway. Let's take the early abiogenesis experiments as an example. Abiogenesis is not really the topic here, but it works as an example of "randomness" being more of a case of "inevitability."We know with pretty decent certainty the conditions of the early, pre-life Earth. As a nice example, we have the moon Titan - it's full of organic compounds like methane, and is very Earth-like except for it's distance from the Sun and the fact that it's a satellite.Given the conditions of the early Earth with basically a "soup" of organic compounds we know to exist naturally without the involvement of life or intelligence, scientists observed that amino acids, the basic building blocks of proteins, formed spontaneously.Was this a "random" occurrence? You could say so from one perspective - nobody guided the reaction, it happened on its own given the correct environment. But it wasn't really. It's just how chemistry works - atoms form themselves into molecules in very predictable and consistent ways. It was "random" in the way that rainfall is random, but inevitable as a result of natural processes given a certain environment, just like rain.Further than that, scientists have conducted subsequent experiments and found that amino acids will even form into proteins spontaneously (a protein is really just a chain of amino acids). Guess what RNA is? That's right - a chain of proteins, and it's essentially what viruses are -some of the simplest forms of life we know of. DNA is the same, but with two helixes instead of one (I know, I'm making this way oversimplified, but it works well enough for the example).We know exactly what DNA does.In much the same way, random mutations are still not random in the way you seem to be using the word. The genetic code is still only made up of certain base pairs, and the order of those base pairs will always, every single time, determine which proteins are produced, and ultimately determine the traits of an organism.Randomness in evolution is also governed by natural selection. Those organisms that just "don't work" won't survive long enough to reproduce, and so their genetic lines will end. The symmetry you believe makes randomness so incredible is simple a beneficial trait - we have two lungs because "backup" organs are more beneficial than single organs. Animals tend to have an even number of limbs because it's more conducive to locomotion and balance.Does that help?

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Every time a fundy breaks the laws of thermodynamics, Schroedinger probably kills his cat.

The rules of the site dictate that we stick to the topic. Drift happens (hell, my most recent post skirts the line at least), but we don't change topic from "eyelids" to "sex" within a thread. It prevents us from discussing completely different topics from that which the thread began, and the posts in threads are limited to about 300 messages.If you'd like to discuss the evolution of gender and sexuality, by all means, start another topic - but I don't see the point personally. We should be able to discuss your incredulity regarding natural processes producing symmetry and so on just fine in a topic about eyelids. You lack of understanding regarding the Theory of Evolution is the real problem, correct? Eyelids are as good an example as any.

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Every time a fundy breaks the laws of thermodynamics, Schroedinger probably kills his cat.

Of course. If such a supreme being can be proven to exist, with evidence, I will believe in it.But as of right now, no convincing evidence has been put forward that proves a supreme being was necessary to form, say, eyelids. I realize it looks like intelligence. But then, so does the water cycle that produces rain - we need rain, right? Clearly there must have been a designer for such a complex process so that we could have rain!This is called putting the cart before the horse - we would not have evolved as we did if rain did not exist, we would have evolved in a way suited to a rain-less environment.Eyelids were not "created" becasue we "needed" them. Those who evolved the precursors to eyelids had a slight advantage over their peers and out-reproduced them, as did every step until modern mammalian eyelids. Those organisms for which eyelids are not really beneficial (fish, for example, who have water washing off their eyes constantly)never evolved them, because such a mutation would have conferred no advantage (meaning if a fish did have the mutation, it would not have out-reproduced its peers, and the mutation would have been irrelevant).The human brain is very adept at seeing patterns even where they do not exist (ie, cloud shapes). The appearance of an intelligent guiding force doesn't mean one actually exists, especially in light of some of the design flaws inherent in the human form.

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Every time a fundy breaks the laws of thermodynamics, Schroedinger probably kills his cat.

Certainly. I only said "tend to," and I'm trying to keep it very simple...partially becasue I've drifted from the topic enough in my explanations as it is Of course. Also, the lack of a separate tube for breathing and consumption which leads to potential choking, etc. An adaptation being beneficial doesn't mean that the lack of the adaptation is necessarily life-imperiling. Would a creature with two hearts have an advantage over a creature with one? Sure...but a possible benefit doesn't mean there is an imperative to develop the benefit, only that the new feature will stick around if it ever appears.Again, I'm just trying to keep it simple so that TheDarin will understand what evolution really means a little better.

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Every time a fundy breaks the laws of thermodynamics, Schroedinger probably kills his cat.

Word games, and a trick question. I see no intelligence in DNA, TheDarin, any more than I see intelligence in the formation of a snowflake. I see the result of natural processes compounding on each other's results for a few million years.I will consider a supreme being's existence when I see a reason to do so. Much like I won't consider that there may be a leprechaun behind me until I have a reason to do so.I didn;t demand that you prove anything. I simply responded to your question with a rational condition. Or do you also think that I should concern myself with the leprechaun? I see just as much evidence of him as I do of a supreme being. The differentiating factor between that which we rationally consider to exist and that which we do not is evidence. A reason to assume somethign exists out of the infinite possibilities contained int he human imagination.Is it possible a deity exists? Certainly. But I don't see any reason to think so. It never claimed to be. They teach you that in your very first science class. Science deals with objective observation and experimentation of natural processes using the five senses. It deals with accuracy. No scientist believes they posses "absolute truth," simply a highly accurate model of the natural processes we observe. molbiogirl's example of the MRI was a good response - remember that we are not at the summit of technology, and it is entirely possible (even probable) that we will some day be able to read the precise word from a person's mind, not just that a word has been thought of.But again, science doesn't deal with that which cannot yet be detected. Science used the five senses to investigate the natural world. If a thing is unfalsifiable, science will not investigate it until such time as we have the capability to make a hypothesis falsifiable.Science is a method of determining accurate models of natural processes. Not determining "truth." It deals in facts and observations and makes testable predictions based on them. No, I dont. I am bound only by that which is observable. I'm sure it's quite wonderful outside of objectivity and rational thought, out there with ghosts and gods and monsters under the bed, but I'd rather stick with what I can verify. No, I'm the result of several million mutations guided by natural selection, as are you, and eyelids.Please stop with the "you know it" nonsense. Christians like to believe that deep down, everyone "knows" god exists. It's not true, TheDarin, and the rest of us find it highly annoying when someone insists it is.Could we please get back to eyelids now? You haven't told us yet what specific problems you have with the explanations we've already given you, and we're drifting pretty far afield. Further drift is likely to get one or more of us suspended, so let's get back to eyelids, shall we? If you'd like to discuss the scientific method further, or broaden the discussion to helping you understand the Theory of Evolution better, please start a new thread.

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Every time a fundy breaks the laws of thermodynamics, Schroedinger probably kills his cat.

Please see our perspective here, TheDarin. This thread is about eyelids. You insist that we haven't answered your issues regarding the evolution of eyelids...but rather than continuing to discuss it until we have answered all of your questions, you've asked us to describe the evolution of a completely different feature.Post counts at this site are limited to about 300, and so we try very hard to keep the topics narrowly defined so that some sort of resolution can possibly be made. Changing the topic of discussion every 20 posts will make us reach the end of the thread very quickly, and will nto answer your questions.Please, tell us what you still don't understand or believe regarding the evolution of eyelids so that we can continue in this thread, or create a new topic that addresses what you'd really like to discuss.

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Every time a fundy breaks the laws of thermodynamics, Schroedinger probably kills his cat.

Let's dispense with the subtle insults, shall we? I responded civilly to you because you seemed to want a genuine discussion. Please don't ruin that. "I don't know" is a perfectly acceptable response. Especially when the technology does not yet exist to allow you to know, one way or another. I'm passionate about finding a pot of gold, too. It doesn;t mean I'll seriously consider the existence of that leprechaun behind me.Besides that, I HAVE explored the existence of a deity. I was a Christian for 25 years - I stopped believing when I realized I had no reason to believe, and I could not differentiate faith in a deity from believing in Santa Claus.I dont expect the Theory of Evolution to answer all of my questions, TheDarin, only those questions relating tot he changes we observe in species over generations. I also don't expect science to answer all of my questions - only those related to the observable world that are testable. Becasue that's not the topic of this thread. There is a thread regarding that topic that is currently active, however, if you'd like to pose your question there. "Why are there two sexes?"Your mockery forces me to say "no." Yes, I believe the evidence shows that eyelids, and human sexuality, are evolved features. The process you mockingly described, however, has very little to do with evolution.

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Every time a fundy breaks the laws of thermodynamics, Schroedinger probably kills his cat.

Yes they did.See how well bare assertions work?Why do you believe eyelids did not evolve? What specific problems do you have with the explanations already given to you?This is the best exercise you can undertake to really understand Evolution - take a single feature, and examine how it evolved and the evidence that shows it.So let's continue the discussion of eyelids, shall we?What should we see if eyelids evolved?One thing we could possibly expect to see would be vestigial remnants of eyelid precursors in creatures that now have eyelids (things like nictitating membranes, for instance). Guess what we find?From Wikipeida:

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The plica semilunaris is small fold of tissue on the inside corner of the eye. It is the vestigial remnant of the nictitating membrane (the "third eyelid") which is present in other animals such as birds, reptiles, and fishes. It is rare in mammals, mainly found in monotremes and marsupials.[12] Its associated muscles are also vestigial.[2] The plica semilunaris of Africans and Indigenous Australians have been said to have slightly larger than other peoples.[2] Only one species of primate -- the Calabar angwantibo -- is known to have a functioning nictitating membrane.[13]

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So, humans have a small structure that is a remnant of the nictitating membrane found in a variety of other creatures.Just as a definition, a "vestigial" structure is one that has lost it's functionality through evolution. For instance, ostriches have vestigial wings - their ancestors had a use for wings, but the wings of ostriches are essentially useless. Humans have the appendix, which is a vestigial cecum - the cecum is used by herbivorous mammals to digest cellulose. The organ in humans has no function (though it seems to get infected pretty easily, and require removal, with no effect on the person it is removed from).Since we posses vestigial versions of the precursors to eyelids, this is evidence that eyelids did, in fact, evolve.

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Every time a fundy breaks the laws of thermodynamics, Schroedinger probably kills his cat.

Perceived rudeness is irrelevant, TheDarin. Actually answering the content of posts, however, is.We collectively have a large number of points and rebuttals that you have not answered. If you really want to debate, or even just learn about Evolution so you can argue against the actual theory, real participation in the thread beyond "you're mean" would be a good start.Personal attacks, btw, are disallowed at the site. Since I'd really like to debate you and help you learn about the Theory of Evolution, I'd rather not see you suspended for things like that.

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Every time a fundy breaks the laws of thermodynamics, Schroedinger probably kills his cat.

First: you don't have nictitating membranes. You have a vestigial remnant of them left over from an evolutionary precursor, but we mammals have eyelids, which are different.Nitpicking aside - you have many, many instinctual reactions that would have evolved together with the formation of different structures, and many, many autonomic functions.You may as well ask when the "connection" with the brain for making your heart beat, or making your lungs breathe form. The simple answer is, the "connection" evolved as the structures did. Your lungs are a great example of an autonomous action that is still partially voluntary (you can hold your breath, but you can't stop your heart for a few seconds, for example).Another, perhaps more similar example is sexual arousal. Human sexual organs have a distinct reaction to nonphysical stimulation - seeing an attractive member of the opposite sex in a state of undress, for example. When was the "connection" made? It evolved as sexual organs evolved.Why do your eyelids feel heavy when it's time to sleep? Because keeping your eyes open for that long would dry them out, perhaps? Or maybe because keeping them open causes too much distraction and would keep you awake constantly (and humans don't do well without sleep). Either way would provide a selective advantage for those who closed their eyes during the sleep cycle. It could also simply be our body's autonomous signal that we need sleep soon, no different from the signals you receive when you've held your breath too long and your lungs start "burning."There also doesn't need to be a "connection" of the sort you are referring to between the brain and your eyelids. The eyelids don't actually get heavy, you know - the relaxed position for the muscles that control them is the open position; it actually requires your muscles to contract to close your eyes. The heaviness you feel is just the result of your subconscious brain trying to start the sleep cycle. The feedback loop of

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(brain decides it's time for sleep) > (brain sends signal to eyelids) > (eyelids get heavy) > (conscious brain detects heavy eyelids) > (conscious brain interprets heavy eyelids as sleepiness)

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is incidental. Our conscious minds are not aware of every autonomous function of our bodies, and we assess our condition along similarly indirect lines all the time.

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Every time a fundy breaks the laws of thermodynamics, Schroedinger probably kills his cat.

Except that evolution has a mechanism. "Goddidit" does not.If you ask why an object fell, and I say "gravity did it," that is fundamentally different from "Goddidit." The workings of gravity are well-known, and attributing a fall to its workings is perfectly reasonable. It even results in some testable predictions: for instance, if the object fell on Earth and discounting any wind resistance, the object should fall at about 9.8 m/s^2 towards the ground. "Goddidit" says nothing.When I say that a feature "evolved," I am similarly referencing the mechanisms and predictions of the process described by the Theory of Evolution - that is, the feature in question should be a slightly modified version of the same feature found in an already existing species, that the similarities between the related structures should be more similar for very closely related species and less similar for distantly related species, and that the feature likely provides some sort of advantage to the organism as opposed to a creature that does not posess the feature.That's a lot more than "Goddidit," don't you think?When I say "the urge to close the eyes must have evolved along with eyelids and the continuing evolution of sleep patterns," it's like saying "the rock must have fallen off of the shelf due to gravity when it was pushed off balance." I don't need to go into the extreme specifics of the evolution of the "heaviness of eyelids" in the former statement any more than I need to describe how gravity works in the latter.Do you believe this behavior, or eyelids, did not evolve? If not, why not?

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Every time a fundy breaks the laws of thermodynamics, Schroedinger probably kills his cat.

Then you have no idea what evolution or a scientific theory are. A scientific theory is a model of an observed process that takes into account all available evidence to make the most accurate predictions possible. Further, to be considered a theory a model must pass through the peer review process and undergo extensive testing of its predictions. If those predictions are slightly off, the model will be modified in the persuit of accuracy. If the predictions are falsified, the model will be thrown out.A scientific theory is quite a bit different from the normal usage of the term.And quite contrary to your statement, each year the mountains of evidence for evolution grows. Hell, the theory only describes the process - evolution by mutation and natural selection has been actually observced. The specific mechanisms described in our model are still tentatative, but that species do change, and new species arise from pre-existing species is an observed fact.If you have evidence that the theory of evolution is being "dismantled year by year," present it. The theory of evolution has literally nothing to do with how life arose int he first place. None. Zilch. Completely different topic. The theory of evolution describes only the process by which new species arise from existing species. Evolution is not the same as abiogenesis, any more than the theory of gravity is also the theory of plate tectonics. No, it's not. If I say "I fixed the TV," you have absolutely no idea how the TV was fixed. You only know that I did it. Incorrect. I was a Christian for the first 25 years of my life, and I accepted evolution even then. I agree, which is why it's sad that you don't know what a scientific theory is, and you clearly haven't researched the theory of evolution because you are confusing it with abiogenesis.

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Every time a fundy breaks the laws of thermodynamics, Schroedinger probably kills his cat.