How Many Mutations Does It Take To Build An Eye?

by hamilcarr 2 Replies latest social current

  • hamilcarr
    hamilcarr

    Inspired by recent discussions on blind salamanders ...

    Side remark:

    Curiously lacking was any discussion by Dawkins of the selection pressure that would have set the process in motion and of the selective advantage of members of more than 399 000 generations of their species would have enjoyed as they served as conduits for this ever-invagination, liquid-filled pair of pockets in their head region (Schwartz, 1999: 361-2).

    Scientific evidence:

    A single gene can turn on a cascade of some 2 500 genes that are required to build an eye (Gehring, 1998: 203).

    Walter Gehring provided evidence that only one regulative gene controls eye development. No endless string of links, but only one master control gene.

    http://en.wikipedia.org/wiki/Walter_Jakob_Gehring

  • funkyderek
    funkyderek

    hamilcarr:

    Curiously lacking was any discussion by Dawkins of the selection pressure that would have set the process in motion and of the selective advantage of members of more than 399 000 generations of their species would have enjoyed as they served as conduits for this ever-invagination, liquid-filled pair of pockets in their head region (Schwartz, 1999: 361-2).

    I don't know what event this is referring to but if the writer was familiar with Dawkins's work, he would know that the evolution of the eye was dealt with in his book Climbing Mount Improbable. In a chapter entitled "The Forty-fold Path to Enlightenment" Dawkins discusses exactly how an eye could evolve, shows numerous "transitional" forms, explains exactly why "half an eye" is better than no eye at all, and provides details of a computer simulation that shows how trivial it is for something like an eye to evolve, which is why it has happened so many times in nature.

    The quoted writer's idea that 399,000 generations were carrying around large useless eyes just waiting for the last piece of the jigsaw to be added so they could see is absolutely absurd, and one doesn't even need to know much about biology or evolution to see that this is so. It's quite obvious that a creature with light-sensitive cells on its body will survive better than one without (in certain environments, of course). If the area containing those cells is indented, the creature can tell which direction the light is coming from. If the indentation is almost completely closed, only allowing a pinhole of light coming in, the creature will be able to make out individual objects. If the opening is covered by a transparent liquid, a clearer image can be produced. If this liquid can be controlled by muscles, then the creature can focus on objects at different distances. Examples of all these stages exist in nature. At every stage, creatures who have such an eye (or proto-eye) have a survival advantage over those who do not. Every stage can be improved by a single point mutation. That is all that is necessary for a complex eye to evolve.

    Walter Gehring provided evidence that only one regulative gene controls eye development. No endless string of links, but only one master control gene.

    That would probably be the gene eyeless* or similar. If it is switched on in a group of cells, those cells develop into an eye. If it is switched off or not working, no eye develops. There are obviously many more genes involved in the actual structure of the eye.

    *Confusingly, genes are normally named according to what happens when they are malfunctioning. Thus the gene that controls the development of the eye is named eyeless.

  • shadow
    shadow

    A few reviews of Climbing Mount Improbable on Amazon.com. Granted these are negative but do mention some of the book's weak points.

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    3.0 out of 5 stars Interesting, but unlikely to win new converts, June 16, 2000
    By "mikeu3" (Cambridge, MA USA) - See all my reviews
    Climbing Mount Improbable is another of Richard Dawkins' popularly-accessible defenses of Darwinism. Dawkins discusses in detail the evolution of wings and eyes as well as the intriguing mutualistic relationship between figs and the wasps that fertilize them, and these more highly zoology-focused chapters are where he is at his best, which might be expected considering that he is a zoologist. He does an excellent job of exposing us to the diversity of wings and eyes throughout the animal kingdom and of using that diversity as an illustration of the power of natural selection. However, there are a number of weaknesses in the book which prevent it from being the sort of airtight argument for Darwinism that he seems to want it to be. He spends a lot of time discussing computer simulations of the evolution of things like spider webs and insects which serve ostensibly to show that random mutation and natural selection is enough to produce what we see in nature today. But these programs are inevitably gross oversimplifications of the matter (he seemed quite proud to note that his insect-generating program used a total of 16, count 'em, 16 genes) and their imitation of natural selection often consists of nothing more than the user picking the specimens in a generation which most resemble the ones which occur in the wild--this obviously biases the whole process and makes it seem like whatever point it is that he's trying to make with these programs (he doesn't make even that very clear) he's arriving at it in part by circular reasoning.

    In discussing the wing, the eye, and the fig, Dawkins purports to be taking the most impressive adaptations in biology and showing that they've all been reached by, as he puts it using the apt metaphor on which the book is based, a gradual slope up Mount Improbable. In the case of the eye, he concentrates on the evolution of its shape and does a solid job at that. However, it seems like the evolution of photocells with light-detecting pigments and the development of the proper neural pathways to interpret signals from the eye would be considerably more substantial achievements than the eye simply attaining the shape it has today, and Dawkins leaves these issues out. Also, Dawkins never really gets around to addressing the issue of how complicated protein molecules like hemoglobin could have come into being through only random mutations and non-random natural selection, an question which, as Dawkins himself mentions, a number of people have some problems with.

    All in all, a lot of Dawkins' writing, especially the final chapter on the fig, is quite fascinating and worth reading in its own right. However, as a defense of evolutionary theory, this book leaves a lot of mighty large holes open and consequently seems unlikely to convince the skeptics.


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    1.0 out of 5 stars Mount Improbable is Mount Impossible, October 25, 2001
    By Ben Holcomb (Wichita) - See all my reviews
    (REAL NAME)
    Richard Dawkins goal in Climbing Mount Improbable was to show how the improbable evolution of life happened on planet earth. He failed miserably. Mr. Dawkins does not show ANY EVIDENCE to support this supposed journey up Mount Improbable. Furthermore, he reveals a glaring ignorance of statistics and fails to inform the reader that the chance of an unguided, undirected form of evolution traveling up the slope of Mount Improbable is statistically zero. If Mr. Dawkins wants to maintain blind faith in the impossible then that is his God given choice; but attempting to pass this nonsense off as science, saying that: "Nothing is as difficult to evolve as we humans imagine it to be."(pg 196) and that: "Even the most difficult problems can be solved, and even the most precipitous heights can be scaled, if only a slow, gradual, step-by-step pathway can be found" (326) is not only misleading and unscientific but is flat-out wrong.

    Now I am sure that many of Mr. Dawkins followers will challenge the statement that he fails to show any evidence to support his claim. However, this is the only conclusion to draw when one looks objectively at this book. For example, in the first chapter, Facing Mount Rushmore, Dawkins differentiates between accident and design. He argues (correctly) that one who knows nothing about Mount Rushmore could conclude it was designed because, even though nature COULD HAVE made it that way, it would be highly improbable for nature to have accomplished it (6). However, Dawkins show a tremendous lack in logic when he proceeds to argue that organisms (or as he calls them "designoid objects") just bear "the illusion of design" (25). He admits that desingoid objects may seem to be designed because of their perfection, "but it is not real design because it has been arrived at by a completely different process" (28) But where is the evidence to support this? Where is the data to support this supposed scientific claim? The evidence is not witnessed by humans because it "is too slow to make an impressive demonstration for impatient and short-lived humans."(30) The evidence for this completely different process can be found in computers, or so argues Mr. Dawkins. Many others, however, strongly disagree. William Dembski, Michael Behe, and Stephen Meyer show why Dawkins computer program fails in their book: Science and the Evidence for Design in the Universe. Neil Broom does likewise in his book: How Blind is the Watchmaker. Royal Truman has even set up a similar computer program and written about why this does not show how organisms climbed Mount Improbable.

    Refer back to the first chapter, and Dawkins concludes that just because nature COULD HAVE created Mount Rushmore, it didn't. It is not probable that nature could create something that looks like four presidents heads. (19) However, Dawkins foregoes this logic throughout the rest of book and argues the exact opposite. For example, Dawkins devotes chapters 4 and 5 to how flying evolved and how the eye evolved. Yet, Dawkins doesn't show ANY EVIDENCE of either occurring in nature. He only points to examples in current organisms and postulates how it COULD HAVE happened. Just because some Australian marsupials are gliders does not prove that some organisms evolved the use of flight. Dawkins creates an hypothetical organism that gradual evolves flaps of skin between the arms and legs. Natural selection could work on this and because this trait may happen to be beneficial, the majority of the population would eventually evolve into something "capable of gliding hundreds of feet, and capable of steering themselves into a control landing." (120) Well that is all fine and dandy, but where is the evidence that this is WHAT HAPPENED, and not just COULD HAVE HAPPENED. Either Mr. Dawkins left this evidence out of the book (highly improbable) or the evidence does not exist (highly probable)!

    Dawkins writes: "The ease with which small animals can float suggests that we have only to assume that flying evolved originally in small animals, and the flying peak of Mount Improbable immediately looks less formidable." (113) "All that matters is that the quantity of light entering the eye should be controlled. When you realize this, the early evolution of the variable pupil ceases to be a problem." (168) Again this is not evidence for the evolution of flight or of the eye. This is merely hypothetical conjecture that Dawkins attempts to shove off onto people all in the name of science. Speculating how something COULD HAVE happened is only scientific if the theory can be tested. Dawkins claims are NOT TESTABLE, they are NOT REPEATABLE, and most importantly they are NOT EMPIRICAL; THERE IS NO WAY TO SCIENTIFICAL TEST HIS HYPOTHESIS SO, THUS IT IS NOT A SCIENTIFIC ARGUMENT.

    Dawkins often used theological arguments to refute creation. Arguing that traits found in animals today, like whales, show that "No sane creator" would have designed them that way. That if whales "had been deliberately created for the sea, they would be very different, and a lot more like fish than they are."(133) But that observation is NOT A SCIENTIFIC OBSERVATION! That is a claim about the character of God. It is amazing, that evolutionists are notorious for labeling creation unscientific because it concerns the supernatural. But they seem to have no problem with using supernatural arguments to SUPPORT their theory.

    This book lacks any scientific evidence to support his claim of the title. Dawkins believes evolution is true, but how do we know this is true? There certainly wasn't any scientific evidence to support it occurring in this book. Dawkins has written that anyone who says they don't believe in evolution is "ignorant, stupid, or insane" (or wicked but he would rather not consider that). However, 90% of the public rejects his form of evolution. Those who do believe in evolution believe in a God directed, guided form of evolution. Tens of Thousands of scientists reject Darwinism. So how can everybody else be wrong? The numbers are growing against Darwinism, and despite what some people say, Philip Johnson is right: Darwinism is a sinking ship, it is only a matter of time before it sinks for good. So keep on telling yourself, Mr. Dawkins that it is just everybody else who is confused. Keep sticking your head in the sand, pretending everyone else is wrong and you and your small group of cohorts are right. That attitude seems to be keen these days with a few individuals over in Afghanistan.
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    1.0 out of 5 stars Imaginative Speculation Plus Computer Games, February 8, 2000
    By a biologist/geologist (Chicago, IL) - See all my reviews
    Dawkins is a master of imaginative storytelling. He also resorts to computer simulation to ostensibly show how living structures could arise from less complex parts. However, his computer-made structures bear only a superficial resemblance, at best, to actual living things, and are orders of magnitude less complex than even the simplest of living things. Conclusion: Molecules-to-man evolution remains, at best, unproven.

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