Image: Photograph by Dan Saelinger. Specimen courtesy of the Eye-Bank For Sight Restoration, New York (www.eyedonation.org)
In Brief
- The eyes of vertebrate animals are so complex that creationists have long argued that they could not have formed by natural selection.
- Soft tissues rarely fossilize. But by comparing eye structures and embryological development of the eye in vertebrate species, scientists have gained crucial insights into the organ’s origin.
- These findings suggest that our camera-style eye has surprisingly ancient roots and that prior to acquiring the elements necessary to operate as a visual organ it functioned to detect light for modulating our long-ago ancestors’ circadian rhythms.
More In This Article
The human eye is an exquisitely complicated organ. It acts like a camera to collect and focus light and convert it into an electrical signal that the brain translates into images. But instead of photographic film, it has a highly specialized retina that detects light and processes the signals using dozens of different kinds of neurons. So intricate is the eye that its origin has long been a cause célèbre among creationists and intelligent design proponents, who hold it up as a prime example of what they term irreducible complexity—a system that cannot function in the absence of any of its components and that therefore cannot have evolved naturally from a more primitive form. Indeed, Charles Darwin himself acknowledged in On the Origin of Species—the 1859 book detailing his theory of evolution by natural selection—that it might seem absurd to think the eye formed by natural selection. He nonetheless firmly believed that the eye did evolve in that way, despite a lack of evidence for intermediate forms at the time.
Direct evidence has continued to be hard to come by. Whereas scholars who study the evolution of the skeleton can readily document its metamorphosis in the fossil record, soft-tissue structures rarely fossilize. And even when they do, the fossils do not preserve nearly enough detail to establish how the structures evolved. Still, biologists have recently made significant advances in tracing the origin of the eye—by studying how it forms in developing embryos and by comparing eye structure and genes across species to reconstruct when key traits arose. The results indicate that our kind of eye—the type common across vertebrates—took shape in less than 100 million years, evolving from a simple light sensor for circadian (daily) and seasonal rhythms around 600 million years ago to an optically and neurologically sophisticated organ by 500 million years ago. More than 150 years after Darwin published his groundbreaking theory, these findings put the nail in the coffin of irreducible complexity and beautifully support Darwin’s idea. They also explain why the eye, far from being a perfectly engineered piece of machinery, exhibits a number of major flaws—these flaws are the scars of evolution. Natural selection does not, as some might think, result in perfection. It tinkers with the material available to it, sometimes to odd effect.
This article was originally published with the title Evolution of the Eye.
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34 Comments
Add CommentI enjoyed the element of Mr Lamb’s piece that was it’s party political presentation to put down the ‘creationists and intelligent design proponents’ by describing the elements of the eye’s structure that are inefficient. Would it be possible to evolve from this a prize to be awarded to whomever had been particularly effective in identifying life support processes or structures that by the ineptitude of their design are a real drag on the affected creature(s). Also, to the description of some wondrous mechanism that ‘obviously’ provides a neat way of meeting a need of the fortunate bearer, would it be possible for your journal to add a paragraph, from an appropriate technician, describing how that need might more elegantly be satisfied with a modicum of thoughtful consideration.
Reply | Report Abuse | Link to thisWhen it comes to the stunning complexity of the eye, I must say that it is amazing to find piecemeal evidence for its evolution. I am not necessarily an advocate of Intelligent Design myself, but I do see how aspects of its theory can be beneficial when it comes to understanding the development of fitness and efficiency. Perhaps it is a misunderstanding on my part, but the evidence presented in this article does not seem to be the final nail in the coffin of ID. What can be said about this evidence is that organisms do evolve and that complexity can come about in a piecemeal way, but our science cannot tell us what caused these beneficial mutations to come about – seeing as that knowledge of this kind is inferential in nature. This being the case, it is still worthwhile to wonder about the process of evolution at the creative or genetic level since we cannot prove whether these changes came to pass because of genetic drift in natural selection or by some kind of faculty for adaptive mutation (no matter how miniscule this faculty may be).
Reply | Report Abuse | Link to thisI am sure that a discussion about intelligent design in any favorable light may upset some readers, and the purest form of its theoretical framework, as I freely concur, can be rather cumbersome when it comes to accepting tenets that seem to be unsubstantiated by facts. On the other hand, I hope to show how our theories of evolution are much easier to handle when their ideologies are not brought to bear in their strongest form possible. The fact that something like the eye can evolve piecemeal is very suggestive that some, if not all, large biological changes can come about through traditional models of evolution; but the fact that something can evolve into a functional whole seems to suggest that there is a point when an organism’s evolution has to reinforce its current state of complexity, whereby random changes start to become less and less likely as this complexity becomes more intricate and more vulnerable to mistakes. This gradual approach to greater efficiency is hard to explain through random means and one starts to wonder why most (not all) mutations seem to occur within the constrained possibilities of necessity (as the article states) or efficiency (like the plasticity of the brain) when the entire plethora of potential is always available to blunderously random mutations.
[This is an excerpt from a fuller response at < http://keithdonald.wordpress.com/2011/06/18/canalized-evolution/#more-132 >. If you have the time to read it I would like to hear your thoughts.]
I wouldn't really call the blog post that I wrote a "response". It is more like an attempt to understand what is being presented in the article here. It may be a little lengthy but it is mainly an attempt to offer questions for some of the things that I do not have any good explanations for. Some of the original questions that I posted on my page may have little vexing at times, and posting my comment here helped me to realize that because I went back and edited my "response" to help alleviate the problem. In any event, my qualms were unintentional because I would really like to understand these evolutionary phenomena more clearly and hope to get some answers from those in the know.
Reply | Report Abuse | Link to thisDear kdonald, evolution by natural selection is blind. There is no design and there certainly is no master plan on the long term. Evolution works through random mutations that may or may not be beneficial for the evolving organism. The GRADUAL IMPROVEMENT of e.g. the eye is explained by evolution if one realizes that also the intermediate stages of development of the eye (from the primitive eye to the eye as it is today) offer some benefits to the organism. In other words, the evolution of the eye is the results of mutation after mutation where better intermediate stages of development have a larger change of survival (and procreation) than less good intermediate stages.
Reply | Report Abuse | Link to thisIn general, there is no single fact that I am aware of that is in favour of intelligent desin. Intelligent design has nothing to do with science. It is a religion.
Best wishes,
"the brain translates into images."
Reply | Report Abuse | Link to thisCan the evolution of brain images be traced?
This seems particular difficult because there are no fossils of these images even for creatures that died recently.
Do computers with artificial intelligence have brain images? Thie is the insinuation of the consciousness contest. Isn't it?
@ Anthony Tarallo
Reply | Report Abuse | Link to thisI understand what you are saying and in the original form of my paper I may have sounded confused about what you are saying. You make a valid point and I agree, but when it comes to mutations that require more than one successive step to become useful, like the eye, I am not sure if randomness can explain the continuity of evolution. As the author of this article states, natural selection does not result in perfection (and he gives examples of various inefficiencies). I tried to be careful to make sure that my argument was not for intelligent design in the theistic or teleological sense. I was not arguing in advocacy of some miraculous creation of a complete and functional eye either. I did, however, try to draw parallels between recent work being done on adaptive mutation and the seeming intelligence of its selection of mutations to adverse environments (this process has also been found to be fallible like our own intelligence and immune system). I also tried to liken the continuity of evolution towards greater efficiency in organs that require more than one chance mutation, like the eye, to something like a sustaining memory which may be morphological in nature.
This brings my question of continuity into better focus though I have to use another one of my questions about intermediary states of evolution. I agree that some mutations may have advantages, but each state is more or less functional in its own state of efficiency (just like the ones that we find in our eyes today). To my untrained eye we can see intermediary states present in multiple family groups like monkeys, cats, birds or what have you. All I was curious about is why there is such an array that can be seen in those types but the same type of array is not present in hominids. All of these animals have similar gene structures for they makeup of their eye, yet the evolution of their eye probably came about in different ways. There is evidence that scientists have found concerning genes (which I could cite) and the untrained eye can see that their eyes are different. So all I would like to know is how something as complex as the eye could have continued to evolve into an efficiently working whole, when the process of its evolution could have been diverted at any point in the same way that these various forms of the same family type have been diverted from any continuous evolution away from their original species.
All I want to know has to do with continuity and how it is possible in a chaotically random paradigm.
Just curious,
keith
I really enjoyed this piece insofar as I'm getting some modern diagnostics for a retinal issue and can appreciate first hand the concept of evolution imbedding defects. Such a state of affairs is quite the strongest counter example (as if we need them) to the ID foolishness.
Reply | Report Abuse | Link to thisHowever, I had to note that our author here makes some logical gaffs in discussion when he refers to evolution "inventing" something. It makes him sound like a creationist in spite of himself. There is no compelling teleology in natural selection, a thing may "emerge" but in no case is it "invented"!
Also toward the close our author points out other "camera" style eyes such as that of the squid or octopus as being independently emergent and free of some of our defects. What needs to be pointed out as well is the fact that, while the common ancestor of us and the octopus didn't even have an eye of any kind, the sequence of data processing for visual information in the optical cortex is essentially identical for man, monkey, cat, and octopus!
The evidence presented here hardly puts the nail in the coffin of ID. The studies referenced start with the assumption of common descent, and then ask "How far back?" The results, then, hardly demonstrate common descent.
Reply | Report Abuse | Link to thisWith that assumption removed, the evidence is against common descent: we are required to believe that the incredibly similar eyes of vertebrates and octopuses evolved independently, and complex image-forming eyes in general are supposed to have evolved hundreds of times! In other words, the phylogeny one would parsimoniously conclude based on eyes is incompatible with the phylogeny based on other evidence.
Oh my. I guess some people will stick with their irrational beliefs in the face all facts and reason.
Reply | Report Abuse | Link to thishuttarl, every point you have made has been exaustively and thoroughly answered in a million different discussions about this topic. Either you have not put any effort at all into learning about this subject, or you have stubbornly decided to ignore whatever facts and reason didn't fit your preconceived preferences.
In any event, five minutes and a few google searches should yield you plenty of information to refute your arguments and lead you towards the facts.... assuming you actually want to know what they are.
Best of luck to you!
If humans were "Intelligently Designed" why do they need 1/3 of their life to sleep?
Reply | Report Abuse | Link to thisI also see no intelligence in overloading our planet with more population than it can support - in that we behave just like bacteria.
This also bears on KDonald's comments
Reply | Report Abuse | Link to this"The evidence presented here hardly puts the nail in the coffin of ID. The studies referenced start with the assumption of common descent, and then ask "How far back?" The results, then, hardly demonstrate common descent."
What 'evidence' would 'put the nail in the coffin of ID'. It is not a falsifiable theory. No amount of evidence will ever put in that metaphoric nail because you can always just respond with "well, the designer waved its magic wand." This is exactly why ID is not a scientific theory. In contrast evolution by variation and selection makes very concrete predictions about the way the world should be. Predictions which easily allow us to determine whether the theory is consistent with what we observe or not.
"With that assumption removed, the evidence is against common descent: we are required to believe that the incredibly similar eyes of vertebrates and octopuses evolved independently, and complex image-forming eyes in general are supposed to have evolved hundreds of times! In other words, the phylogeny one would parsimoniously conclude based on eyes is incompatible with the phylogeny based on other evidence."
Did you read the article? What evidence is against common descent? The eyes of all extent chordates (the group which includes hagfish, lampreys, and vertebrates as well as some other groups) are consistent in structure, exactly as evolution would predict. Going further we see that all bilateria (all animals above the grade of cnideria and certain types of 'worms') share a number of features of their visual systems. As the article noted there are specific receptor proteins and cell lineages in common.
I'd point out certain other interesting points which are not noted in the article. The nervous systems in all grades of animals which have them are derived from the same cell line as the skin. This seems quite logical and easily fits in with the general theory. We can hypothesize the most primitive bilaterian state, a tube shaped organism with a through gut, a skin, some kind of motility (muscles), and specialized cells on the skin which acted as sensors (chemical, thermal, light, touch, whatever). In the simples case these cells signaled the muscles, allowing our hypothetical organism to react. Over time the sensor cells elaborated into sensors and signaling/communication cells (neurons). It is then easy to see how a 'light sensing patch' would be organized. From there the article outlines further developments. All very consistent with common descent and evolution.
Additional helpful information can be found in Nick Lane's "Life Ascending" which delves into the genomic evidence. Some of the skeptical commenters seem to focus on fossil evidence without perhaps being particularly familiar with the use of genomic techniques. Lamb discusses this to some degree in the full Sci Am article.
Reply | Report Abuse | Link to thisRe: "Direct evidence has continued to be hard to come by."
Reply | Report Abuse | Link to thisDr. Lambs admission puts him in some impressive company:
"Darwin himself considered that the idea of evolution is unsatisfactory unless its mechanism can be explained. I agree, but since no one has explained to my satisfaction how evolution could happen I do not feel impelled to say that it has happened. I prefer to say that on this matter our information is inadequate."
[W. R. Thompson, F.R.S. 1956. Introduction. In: Charles Darwin. Origin of Species. Everyman Library No. 811. London: J. M. Dent and Sons. Reprinted with permission. Evolution Protest Movement. 1967. NEW CHALLENGING ‘INTRODUCTION' TO THE ORIGIN OF SPECIES. Selsey, Sussex: Selsey Press Ltd., p. 12]
This document, produced by the Discovery Institute (or some such) dropped out of the public eye some time ago. Perhaps it is time to reveal the true face of the so called Intelligent Design movement once again:
Reply | Report Abuse | Link to this****://***.antievolution.org/features/wedge.pdf
Le Spaz d'Argent: I can understand your frustration trying to post with referring to another web-site. You used a good solution, but I was permitted to use www as part of my reference. Perhaps now they may block this to.
Reply | Report Abuse | Link to thisWhen you enter a web address you do not need to enter anything before the 3Ws, they H bit is a descriptor of the document format. The TP or TPS at the end is important for you, it tells you if the site is secure or not. You don't want to do internet banking or purchasing on a site without the S at the end of the document format. Remember the cyber criminal does not see this as a problem.
Rfast Jr. Inefficient is a gross understatement. Do you realise the retina is back to front in all mammalian eyes? And that's not the end of it. The whole human body is a mess, the vagus nerve is another example.
Reply | Report Abuse | Link to thisPS: I got this most of this info. from a physics textbook. Richard Feynman did not believe in compartmentalising science. You need to know a lot of all the sciences before you concentrate on some tiny part, yes you even need botany.
Sorry to disillusion you. There is absolutely, positively no god. We are just like the other creatures around us the result of natural selection.
kdonald: That was a long article you pointed to. However it fails to understand that natural selection is an unforgiving, unthinking, uncaring process.
Reply | Report Abuse | Link to thisWe do suffer mutations all the time, very very few benefit us, those that damage us are eliminated since the bearer of the mutation dies and does not reproduce. Bad mutations are eliminated by death.
That is why I get so upset when doctors save and then help carriers of these damaged genes to reproduce. Example: A young girl with a skin condition that causes severe scarring of the skin brought on by excessive growth of epithelial cells, was treated by rubbing down the skin for hours every day to do away the excessive cells, the treatment worked, she survived (normally they die, late in childhood). She then found herself a partner with the same condition and has 3 children, all with the same condition. Bad Medicine!
And so the simple-minded Creationists are defeated on their final and last stand: that the human eye is so complex that it could not have evolved, but must have been created by some. . .what? some "Master Clockmaker"?.
Reply | Report Abuse | Link to thisAll that position illustrates is that they have not the scientific or intellectual horsepower to imagine such an evolution, and so think they can convince others to be equally ignorant, and thus adopt religions' nonsensical ascertations.
Very unconvincing. Typical non-falsifiable pseudo-science, equivocation and tautology.
Reply | Report Abuse | Link to this"Oh my. I guess some people will stick with their irrational beliefs in the face all facts and reason." Spoken like a true Darwinian votary.
The problem we have here is the taxidermists and stamp collectors are driving the arguments regarding life's origins and development. The physics of life refutes any naturalistic origin of life, particularly the creation and development of the most complex information sytem in the known universe by undirected, random, irrational processes.
Wow! thank you so much Scientific Earthling. The very first time anyone has responded to one of my, infrequent, comments. Thank you very much indeed.
Reply | Report Abuse | Link to thisIt is also a quite splendid demonstration of a dictum of Mr Wilde's: Every reader is a translator, every listener an interpreter.
This diffident, inadequately equipped bunch of hadrons and bosons (BOHB) doesn't want to communicate anything that suggests the existence of some essence peculiar to it, let alone that of the existence of something that doesn't have a particle to represent it. This BOHB intended to suggest that the total irrationality and lack of purpose in the way that these particles happen to aggregate, in what several BOHB's define as living things, should be applauded with an award to those who demonstrate some of the greater idiocies of the process.
Bill,
Reply | Report Abuse | Link to thisYou are again trotting out that arch creationist Professor Thompson, who somehow reconciled his scientific profession with his religious belief. Just like you, he was a devout Catholic and his attachment to Church doctrine showed in the introduction that you keep quoting from.
What exasperates me about these ID debates is that they are fuelled by a fundamental error made by Darwin and perpetuated by generations of biologists. Darwin's central error was his decision that external conditions had no direct effect. Instead, he attributed change to superior internal qualities that resulted from emergence of variations that favoured individuals in a struggle for existence.
The day before publication of Origin Thomas Huxley wrote to Darwin supporting the central proposition of evolution of current species from common origins, but questioning rejection of the effect of external conditions. Huxley was right.
Most present day biologists would agree that external conditions have major effect, but they continue to apply assumptions based on rejection of their effect. This is not semantics, it goes to a fundamental question of whether species are shaped by changes in external conditions that eliminate individuals unable to survive the change (a logical and credible explanation) or whether change results from personal qualities that favour individuals in competitive struggle that results in the extermination (Darwin's term) of unimproved individuals.
As Darwin rightly pointed out, Natural Selection has difficulty explaining how a complex organ such as an eye could evolve. Their attachment to an explanation that rejects the only factor capable of providing direction to evolution is the reason that the biological sciences have to maintain rules that there is no direction in evolution.
Apparently complex organs such as eyes, hands or brains evolve magically by chance and the lucky species works out how to use it.
Organs and species adapt intelligently to external conditions. They are not designed by some external metaphysical designer, but a simple, natural mechanism. Variations happen randomly and individuals do what they do. External conditions determine which behaviours enable individuals to survive in those conditions. The demise of individuals unable to survive adapts a species to the conditions, the greater the pressure, the more closely adapted.
The large holes in the assumptions of biology created opportunities for promoters of ID to step into. Don't blame IDers for filling the holes, blame biologists for creating them.
@tharriss, I actually thought huttarl made some good points, but instead of trying to answer them, you simply redirect to Google. Why not provide the answers here so we can discuss them?
Reply | Report Abuse | Link to thisSo it is now claimed that we can now explain how our eyes evolved "from a simple light sensor." Two questions: (1) What is "simple" about a light sensor? (2) What did the light sensor evolve from?
Reply | Report Abuse | Link to thisIn an accompanying article, you report how scientists are using their intelligence to create a bionic eye. Yet it is claimed no intelligence was necessary to create the real thing. There's something illogical here!
There are at least two major problems with the arguments presented in this article. One is that in constructing his argument the writer assumes the truth of what he is claiming to provide evidence for, thus invalidating the whole thing. The second is that, in any case, the structure of the eye is the least of what evolution theory has to explain. The vertebrate eye requires an unimaginably complex visual system in order to function - the retina is the least of it. Without the brain connections no vision is possible. 50 years of intense research into vertebrate vision has revealed many interesting aspects of the system but has not brough us any nearer to knowing how we, or any other vertebrates, actually see. The picture has got more complex as time has gone on. I'm afraid there is no nail in the coffin - quite the reverse. Creatures have visual systems suitably designed for their visual needs and evolution theory has no explanantion for it and no supporting evidence. The visual system as a whole is what must be explained.
Reply | Report Abuse | Link to thishoamingin,
Reply | Report Abuse | Link to thisWe've been down this road. You're assertion that a creationist was allowed to write the "Introduction" to one of the 1956 editions of "...Origin of Species..." in order to foster debate was unconvincing to me then and remains unconvincing to me now. Here's a quote you can't legitimately attribute to a creationist:
"There is nothing original in the objections deployed by [creationist] books, just the old favourites ("The eye is too complicated to have evolved by blind 'chance'", and the rest) that Darwin himself raised - and demolished."
[Prof. Richard Dawkins. 1985. What was all the fuss about? NATURE Vol. 316, p. 683]
A comparison of Prof. Dawkins' assertion with a quote from the text on this web page would seem to be in order:
"Indeed, Charles Darwin himself acknowledged in On the Origin of Species—the 1859 book detailing his theory of evolution by natural selection—that it might seem absurd to think the eye formed by natural selection. He nonetheless firmly believed that the eye did evolve in that way, despite a lack of evidence for intermediate forms at the time."
Two questions come immediately to mind: (1) What evidence has been provided since 1859? (2) When did belief become part of the language of science?
Stating that, "Organs and species adapt intelligently to external conditions," does not begin to address the far more fundamental question of the alleged evolution of the organism itself. If the typical biologist, as you point out, cannot properly explain the origin of an organ, how can anyone take a biologist seriously who promotes the evolution of the biological organism in possession of the organ in question? Please explain what you mean by intelligent adaptation.
Incidentally, Prof. Thompson concluded his "Introduction" as follows:
"But to understand our own thinking, to see what fallacies we must eradicate in order to establish general biology on a scientific basis, we can still return with profit to the source-book which is The Origin of Species."
Wow, a stunning piece of Darwinian fundamentalist clap trap! Such as has been written over and over again but adding some new makeup and putting some shiny but unconvincing almost new clothes over it doesn't help.
Reply | Report Abuse | Link to thisSame old just-so-story wrapped up to convince the unthinking and highly gullible materialists.
When will the Darwinistas learn at least something about the nature of encoded information, combinatorial dependencies and statistical mechanics?
Never met one yet that had clue on any of that.
tharriss:
Reply | Report Abuse | Link to thisWrong on every claim in your pathetic "rebuttal" to huttarl.
Nothing is more irrational than Darwinian fundamentalism, as you thankfully demonstrate.
You must be another blind follower of the blind materialist right?
So the universe created itself out of nothing as well huh?
Tell us, what is the total energy of nothing? Duh.
The eye is complex but is the sight mechanism complex.
Reply | Report Abuse | Link to thisI am a creationist but I see no reason to not see in different kinds of eyes the true equation of sight.
Yes it seems impossible for evolution to have balanced components in making sight in the kinds we have.
I would add further its not good enough to say the "brain' processes images.
What's that mean.?
I note people can SEE in their dreams and any vivid memory topic. could this simply be what happens in our heads in processing the data from the eyes. Is it possible we don't get images but only memories of what we look at? Is the retina a memory chip?
Just trying to figure it out as blindness etc is not cured.
Do *you* actually want to know what the facts are, or is this a one-sided discussion where you're already right, and only those who disagree with you need to evaluate their position?
Reply | Report Abuse | Link to this"A few google searches" is a bit broad of a basis for making progress in discussion. If you have an article in mind that you find convincing, please post a link to it, and indicate which evidence and interpretations in it you feel are compelling.
I'll start... In this response to the SA article: http://www.evolutionnews.org/2011/06/scientific_american_makes_bold047651.html, it is pointed out that Lamb's thesis is "all based upon one big assumption: that biological tissues are innately plastic. Little attention is given to the biochemical and molecular conundrums which confront such scenarios." The author then lays out specific design details that have to be addressed in order for each "simple" change to be effective and not disastrous.
Regarding the falsifiability of ID: Since Lamb claims to have falsified ID (is that not what "nail in the coffin" means?), but you claim it is unfalsifiable, it is Lamb you are arguing with here.
Reply | Report Abuse | Link to thisID is defined by its proponents as "the theory that nature gives scientific evidence of purpose and design" (spectator.org/archives/2011/06/24/answering-the-dreaded-evolutio).
As such, it is arguable that the theory as a whole is not falsifiable on evidential grounds: you can never completely demonstrate that no X exists (where in this case, X is scientific evidence of purpose and design). However, when someone presents an example of X as evidence for the theory, that particular example can well be falsified. Irreducible complexity is an example of X, and seems to be a focus of this SA article.
More on IC and the falsifiability of Darwinian evolution here:
www.evolutionnews.org/2011/03/michael_behes_critics_make_dar044511.html
"In contrast evolution by variation and selection makes very concrete predictions about the way the world should be. Predictions which easily allow us to determine whether the theory is consistent with what we observe or not."
One such prediction is that early forms of animals and organs should in general be simpler, and later forms, more complex. Yet the literature of paleontology and molecular systematics is littered with discoveries that complex organ A or advanced creature B emerged "much earlier than thought"... indeed, much earlier than predicted by evolutionary models... and is followed by stasis. An example regarding the eye is in this article, to be published in Nature: "New fossils demonstrate that powerful eyes evolved in a twinkling" (www.physorg.com/news/2011-06-fossils-powerful-eyes-evolved-twinkling.html). "Their discovery reveals that some of the earliest animals possessed very powerful vision; similar eyes are found in many living insects, such as robber flies. Sharp vision must therefore have evolved very rapidly, soon after the first predators appeared during the 'Cambrian Explosion' of life that began around 540 million years ago."
(cont'd...)
(cont'd)
Reply | Report Abuse | Link to thisDoes this fossil evidence contrary to predictions cause the authors to question evolutionary models? No, that's not allowed. Instead the authors rationalize, "Given the tremendous adaptive advantage conferred by sharp vision for avoiding predators and locating food and shelter, there must have been tremendous evolutionary pressure to elaborate and refine visual organs." Note this explanation is not based on evidence, but is required in order to protect the theory *from* the evidence.
And you find this epicyclic explanation is inconsistent with other evidence: If such pressure is responsible for driving eye evolution, why did camera eyes supposedly evolve four times within the clade of snails, "which at first sight might be a little unexpected, as the need for well-developed eyes in these usually slow-moving creatures is not immediately obvious" (www.mapoflife.org/topics/topic_1_Camera-eyes-in-vertebrates-cephalopods-and-other-animals/)?
The evidence I was referring to in my comment is the ongoing, systematic conflict between phylogenies based on morphology vs. molecular analysis, and between molecular analyses based on different genes. "The fundamental problem for neo-Darwinism is that phylogenetic trees based upon one gene or characteristic will often conflict with trees based upon some other gene or characteristic... Many studies (like this one) thus use many genes in hopes to avoid the conflicts between trees based upon individual genes or proteins. They must use this method because some genes are telling the wrong phylogenetic story; by averaging out the genetic signals, the theory says that you'll find the true phylogenetic history."
(www.evolutionnews.org/2008/03/more_troubles_in_the_tree_of_a004966.html#more)
Darwin predicted a hierarchically branching "Tree of Life". But the evidence shows that there is no single phylogenetic arrangement that fits the evidence (even if you only consider eukaryotes).
www.evolutionnews.org/2010/03/testing_the_orchard_model_and032481.html
www.evolutionnews.org/2010/12/but_isnt_there_lots_of_other_d041111.html
(cont'd)
(cont'd)
Reply | Report Abuse | Link to thisWhen there are multiple conflicting proposed phylogenies, each supported by certain morphological or genetic similarities but not by others, one phylogeny is picked as the winner. What happens to the similarities that support the losers? They must be put down to "convergent evolution". Researchers do not then dwell upon the possibility that the "winning" hypothesis could just as easily be put down to convergent evolution... indeed the evidential difference is often very small.
www.evolutionnews.org/2011/03/inconvenient_fungus_genetic_da045301.html
Thus we end up with many embarassing "convergences": "The remedy [to spherical aberration] is to alter the refractive index of the lens systematically from the centre to the margin, and several groups have independently arrived at this solution." (www.mapoflife.org/topics/topic_1_Camera-eyes-in-vertebrates-cephalopods-and-other-animals/)
In other words, the theory is not consistent with what we observe. If evolution were falsifiable, as you claim, it would have been abandoned many times over by now.
Trevor D. Lamb's article Evolution of the Eye reminds me of an even greater scientific heresy than ID - that is, Haeckel's discredited theory of recapitulation: "Ontogeny recapitulates phylogeny". Does the development of the human eye in embryo recapitulate its phylogenetic history? I notice that the word "recapitulation" does not occur in the article. But it does say: "Aspects of the embryonic development of an individual are known to reflect events that occurred during the evolution of its lineage". Clarification, please.
Reply | Report Abuse | Link to thisTrevor D Lamb (Scientific American, July 2011) argues that the vertebrate eye is a bad design. Indeed, he says "if engineers were tobuild an eye with the flaws of our own they would be fired".
Reply | Report Abuse | Link to thisThe "inside out" retina is not a flaw. It allows the highly-metabolic photoreceptors to be in intimate contact with the pigmented Retinal Pigment Epithelium RPE, who's role is to nourish and remove their waste products, provide structural support for the long and slender structure (which itself allows higher "resolution" of the retinal mosaic), and it prevents light bouncing back inside the eye, reducing glare and multiple imaging. The RPE itself is nourished by the underlying dense vascular network called the choroid. If not behind the sensory retina where else would Lamb put the heavily pigmented and opaque RPE: the photoreceptors HAVE to be in front of the RPE, otherwise no light will get to them! Then how does one get the visual signal out of they eye without disrupting the RPE and traveling through the dense choroidal blood supply, other than having the signal travel backwards and out via the optic nerve?
What about light scatter, Lamb argues? Light scatter passing through the inner retina is negligible due to the Stiles-Crawford effect and the fiber-optic properties of the Muller cells. Also any light lost due to absorption by the inner retinal cells is negligible, due to the transparent nature of the inner retinal cells and the photoreceptors can detect a single quantum of light anyway.
The retinal architecture is elegant and functional. A series of random mutations may have resulted in its formation. But to suggest its a "flawed design", seems to be more about an agenda rather than good science.
Refs:
1. Walter Stanley Stiles and Brian Hewson Crawford (1933), "The luminousis efficiency of rays entering the eye pupil at different points," Proc. R. Soc. Lond B 112:428-450.
2. Müller Cells Are Living Optical Fibers in the Vertebrate Retina Kristian Franze, Jens Grosche, Serguei N. Skatchkov, Stefan Schinkinger, Christian Foja, Detlev Schild, Ortrud Uckermann, Kort Travis, Andreas Reichenbach and Jochen Guck Proceedings of the National Academy of Sciences of the United States of America Vol. 104, No. 20 May 15, 2007), pp. 8287-8292.
3. Hecht, S., Schlaer, S., and Pirenne, M. H. (1942). Energy, quanta and vision. Journal of the Optical Society of America, 38, 196–208.
4.Choi C.Q Spooky Eyes: Using Human Volunteers to Witness Quantum Entanglement http://www.scientificamerican.com/article.cfm?id=human-eyes-entanglement