Evolution of the Eye and Senses (formerly "Just Some Thoughts")

This isnt to provoke anyones anger I just have a few thoughts on this long debated topic.For the evolutionists:Eyes... How is it possible that a single celled organism evolved to have photosensitive cells and then further to develop eyes.
I understand that your evolution is based around the fact that a genetic mutation that enables an organism to function better is then passed on because that organism becomes dominant. How does an organism that small develop photosensitive cells. This had to have been early in the "pre-historic" times because if everything evolved from the same organism, because every organism known today (with the exception of eyeless fish) has eyes.Basic senses... To add to the eyes thing. Basic senses had to have developed sometime within the time period of the eyes because if they had developed on their own in different species would they not all function differently? So how would a polar bears senses be different from that of african lion, the answer is, they arent, they work just the same. but in 2 totally different parts of the world.Im not here to piss anyone off, i just want to know if someone has come up with answers to these questions.... Changed title. --AdminThis message has been edited by Admin, 04-07-2005 11:21 AM

The anser to your question is "Yes, both issues you have brought up have been explained, are rather trivial and are covered many many times here."You OP though is well written, clear and consise. I will promote it based on those factors even though the subject matter is covered in thread after thread.At the bottom of this post are some links to tips that will help make your stay here more enjoyable and productive.Again, welcome and thanks for writing a very well constructed initial post.

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Thread moved here from the Proposed New Topics forum.

Since the main thrust of you OP is regarding eyes could I suggest that the thread title might be better has "The Evolution of Eyes"?If you agree say so and we can change it (I don't remember if you can yet or not).

Hello, castis.Yes, this subject has been beaten to death. Darwin himself discussed a possible scenario for the evolution of eyes, based on the "partial eyes" that exist in the animal kingdom.No, the proto-eye did not have to begin so far back. It is believed that eyes evolved in 14 different linneages, independently of one another.The evolution of the eye from no eye has been modelled on a computer. In each step of the model, the new version of the eye is only very slightly different from the older version. And the new version is a little better at seeing than the old version. So it is possible for there to be a sequence of ever-so-slightly better eyes.You are correct (if I am reading you correctly) that the eye has to start with some cells have a photosensitive chemical. I think that the photosensitive pigments in the human eye are very slight variations of proteins involved in locomotion in single cells. I will let people more qualified than I discuss this more detail.

Can we not see this even in things without anything like what we would consider a nervous system or senses? Don't plants also show photosensitivity?

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Aslan is not a Tame Lion

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Can we not see this even in things without anything like what we would consider a nervous system or senses? Don't plants also show photosensitivity?

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There are quite a few unicellular organisms (single celled critters) that are sensitive to light, and many can direct themselves away or into light using photosensitive reactions. Just a quick scan of pubmed, a photo-reaction in the ciliated protozoan Blepharisma creates ion flow within the cytoplasm, not unlike the ion flows created across the membrane in mammalian retinal cells:

I think what he's asking is, what's the earliest ancestor with recognizable features that would go on to become eyes? I don't presume that its a unicellular organism, right?

With the exception of eyeless fish, yes. And almost all the other organisms living on this earth.For some perspective, please take a look at this picture of the phylogenetic tree of life. The organisms with eyes are found only in the twig labeled "Animals".

It would be hard to say. Eyes developed, I believe, before the Cambrian, before animals had easily fossilizable body parts.But, in a very technical sense, the first animal (or ancestor) that had a recognizable part that formed the first basis for an eye may have been something like Loudmouth's Blepharisma. I think this certainly counts.

this is an OLD argument.someone breifly mentioned it before, but i'll give you a specific reference. i believe it's chapter 6 of "the origin of species" by charles darwin, entitled "problems on theory." it was pages 152-154 in the last copy i borrowed from the library.here's the important section from an online version of darwins "the origin of species:

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Organs of extreme perfection and complication. To suppose that the eye, with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest possible degree. Yet reason tells me, that if numerous gradations from a perfect and complex eye to one very imperfect and simple, each grade being useful to its possessor, can be shown to exist; if further, the eye does vary ever so slightly, and the variations be inherited, which is certainly the case; and if any variation or modification in the organ be ever useful to an animal under changing conditions of life, then the difficulty of believing that a perfect and complex eye could be formed by natural selection, though insuperable by our imagination, can hardly be considered real. How a nerve comes to be sensitive to light, hardly concerns us more than how life itself first originated; but I may remark that several facts make me suspect that any sensitive nerve may be rendered sensitive to light, and likewise to those coarser vibrations of the air which produce sound.

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In looking for the gradations by which an organ in any species has been perfected, we ought to look exclusively to its lineal ancestors; but this is scarcely ever possible, and we are forced in each case to look to species of the same group, that is to the collateral descendants from the same original parent-form, in order to see what gradations are possible, and for the chance of some gradations having been transmitted from the earlier stages of descent, in an unaltered or little altered condition. Amongst existing Vertebrata, we find but a small amount of gradation in the structure of the eye, and from fossil species we can learn nothing on this head. In this great class we should probably have to descend far beneath the lowest known fossiliferous stratum to discover the earlier stages, by which the eye has been perfected.

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In the Articulata we can commence a series with an optic nerve merely coated with pigment, and without any other mechanism; and from this low stage, numerous gradations of structure, branching off in two fundamentally different lines, can be shown to exist, until we reach a moderately high stage of perfection. In certain crustaceans, for instance, there is a double cornea, the inner one divided into facets, within each of which there is a lens shaped swelling. In other crustaceans the transparent cones which are coated by pigment, and which properly act only by excluding lateral pencils of light, are convex at their upper ends and must act by convergence; and at their lower ends there seems to be an imperfect vitreous substance. With these facts, here far too briefly and imperfectly given, which show that there is much graduated diversity in the eyes of living crustaceans, and bearing in mind how small the number of living animals is in proportion to those which have become extinct, I can see no very great difficulty (not more than in the case of many other structures) in believing that natural selection has converted the simple apparatus of an optic nerve merely coated with pigment and invested by transparent membrane, into an optical instrument as perfect as is possessed by any member of the great Articulate class.

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He who will go thus far, if he find on finishing this treatise that large bodies of facts, otherwise inexplicable, can be explained by the theory of descent, ought not to hesitate to go further, and to admit that a structure even as perfect as the eye of an eagle might be formed by natural selection, although in this case he does not know any of the transitional grades. His reason ought to conquer his imagination; though I have felt the difficulty far too keenly to be surprised at any degree of hesitation in extending the principle of natural selection to such startling lengths.

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It is scarcely possible to avoid comparing the eye to a telescope. We know that this instrument has been perfected by the long-continued efforts of the highest human intellects; and we naturally infer that the eye has been formed by a somewhat analogous process. But may not this inference be presumptuous? Have we any right to assume that the Creator works by intellectual powers like those of man? If we must compare the eye to an optical instrument, we ought in imagination to take a thick layer of transparent tissue, with a nerve sensitive to light beneath, and then suppose every part of this layer to be continually changing slowly in density, so as to separate into layers of different densities and thicknesses, placed at different distances from each other, and with the surfaces of each layer slowly changing in form. Further we must suppose that there is a power always intently watching each slight accidental alteration in the transparent layers; and carefully selecting each alteration which, under varied circumstances, may in any way, or in any degree, tend to produce a distincter image. We must suppose each new state of the instrument to be multiplied by the million; and each to be preserved till a better be produced, and then the old ones to be destroyed. In living bodies, variation will cause the slight alterations, generation will multiply them almost infinitely, and natural selection will pick out with unerring skill each improvement. Let this process go on for millions on millions of years; and during each year on millions of individuals of many kinds; and may we not believe that a living optical instrument might thus be formed as superior to one of glass, as the works of the Creator are to those of man?

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and i'm sure you've read this part:

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If it could be demonstrated that any complex organ existed, which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down.

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but not this part:

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But I can find out no such case. No doubt many organs exist of which we do not know the transitional grades, more especially if we look to much-isolated species, round which, according to my theory, there has been much extinction. Or again, if we look to an organ common to all the members of a large class, for in this latter case the organ must have been first formed at an extremely remote period, since which all the many members of the class have been developed; and in order to discover the early transitional grades through which the organ has passed, we should have to look to very ancient ancestral forms, long since become extinct.

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We should be extremely cautious in concluding that an organ could not have been formed by transitional gradations of some kind. Numerous cases could be given amongst the lower animals of the same organ performing at the same time wholly distinct functions

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Why do ciliate researchers insist on viewing voltage gated ionic chanels as "neuron" like and insist on discussing the equivalent of neuropeptide transmitters in that branch below fungi,plants and animals?I suspect that we dont have the proper understanding of the electrotonics and I wonder how that might be univocal (only remaining vestige in science lingo of this "eye") with Maxwell's sense in the word.But yes, it would be a strech to call chrophyll an "EYE". But if the whole thing is fishy well....

I think this is analogous to analogizing things from the macroscopic everyday human world onto the microscopic. Like: calling some proteins "chaperones" or calling a stand of RNA a "messenger."These guys may be taking it too far and trying to analogize structures/functions within single cells to jobs that whole cells do?Or are they saying that whenever there is some significant electric effect in a cell that it is all so similar that they can call it "neuron-like" as if neurons were the archetypal cells housing pronounced electric effects? Or are they saying that cilia act in the same manner as neurons, maybe in the way they "fire" a signal?Anyway, however they do it, analogies are always misleading to some degree.{shrug} whatcha gonna do?

Your last two suggestions seem most probable to me. But the gentlemen might not be in possession of more knowledge than is too good for them , if for instance contrary evidence sans some things I, BSM, have said, that there is no actual generatio heteronmya. I would be trying to say that this is false.
see
Kant Critique of TJ section80

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We may call a hypothesis of this kind a daring venture of reason, and there may be even of the most acute naturalists through whose head it has not sometimes passed. For it is not absurd, like that generatio aequivoca by which is understood the production of an organized being through the mechanics of crude unorganized matter. It would always remain generation univoca in the most universal sense of the word, for it only considers one organic being as derived from another organic being, although from one which is specifically different; e.g. certain water animals transform themselves gradually into marsh animals and from these, after some generations, into land animals. A priori, in the judgment of reason alone, there is no contradiction here. Only experience gives no example of it; according to experience all generation that we know is generatio homonyma. This is not merely univoca in contrast to the generation of unorganized material, but in the organization that the product is a like kind to that which produced it; and generatio heteronyma, so far as our empirical knowledge of nature extends, is nowhere found.

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I am tempted to think that Mendel might have thought up the double signification of hybrid and parent in a cross fertilized generation from Kant section 81 on a certain occasion,{"only to leave to its parent its development and nourishment", "would concede to neither parent", "production of hybrids could"}which I used to reach/write the above comment, but there are so many things I need to say to EVCers that I dont have the time to work it all up to the point of a discussion about this as NOT an "analogon of art"(Kant section 65 Critique of Teleological Judgement). Establishing a general 'duty' and specific "obligation" among EVC posters is not a plan that would be easily acommpished could "analogon of life" (op cit)be more properly recognized. I wish it could be.
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"To speak strictly, then, the organization of nature has in it nothing analogous to any causality we know. We can conversely throw light upon a certain combination, much more often met with in idea than in actuality, by means of an analogy to the so-called immediate natural purposes. In a recent complete transformation of a great people int a state the word organization for the regulation of magistracies, etc., and even the whole body politic, has often beeen fitly used. For in such a whole every member should surely be purpose as well as means, and while all work together toward the possiblity of the whole, each should be determined as regards place and function by means of the Idea of the whole.[Kant probably alludes here to the organization of the United States of America]."same section immediately op. cit.
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It would be needed to describe the difference between an ideal and pathologic conditions in ELEVATING the desire in judgements that need not be artistic as IN THE POWER of the people, appearences that might not be within the topic of this thread, but circulating with FREE will for sure. I would like to think I have given the example below but so far not one is following me yet. It might have to be through the skipping generation facts, if they exis,t that this must be rewritten into, to get it understood. Evos seem to be obsessed that natural selection IS alike causally to artifical selection that they cant seem to bring themselves to find the educt production of selection in nature ON PURPOSE as the baramin product and behind this determine, not merely reflect on, the statistical physics (heteronmya through gladyshev's law in the perfection of the Mendel binomial as the sign of life (not cilia as neuron etc))) from the phenomenological thermodyanmics! Instead, Gould simply talks about the women's pelvis size. I might have found it.

I heavily appreciate how understanding everyone was with my questions.I will definately read all of the links and such posted and get back to everyone with probably more questions on my findings.