How the Blind Watchmaker Made Eyes

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Since the days of Darwin, eyes and evolution have been an irresistible topic for scientists and amateur authors alike. British biologist St. George Jackson Mivart was initially a supporter of Darwin, but when his Catholic religion caused conflict with Thomas Henry Huxley in 1871, he changed to a critic. Mivart’s critique focused on the issue of the perfection of the human eye and how he could not fathom how it could have evolved by natural selection and random chance (a point still raised by creationists today who know nothing about comparative biology).

 

In later editions of On the Origin of Species, Darwin specifically addressed Mivart’s criticism and carefully explained how the incipient stages of complex structures like the eye could be useful, and could have evolved by small steps; it did not require a giant leap to the complexity to develop the human eye. As Darwin first showed, nature is full of examples of every kind of photoreceptor, from simple light-sensitive cells to eyespots to simple eyes with no lenses, to a variety of solutions of seeing with more and more complex eyes. Once you arrange these solutions in an array, it is only a small step from one to the next, more complex eye. (Indeed, many animals actually show this transition during their embryonic development as their eyes change, and in some organisms, the eyes develop differently in males and females). In fact, the passages where Darwin talks about the eye are one of the most frequently “quote mined” by creationists trying to distort Darwin’s meaning, because they quote only the beginning of the paragraph where Darwin is setting up the creationist position in order to shoot it down the in the rest of the passage (which creationists never quote). Here is the first section that creationists quote (On the Origin of Species, 6th ed., 1872, 143–144):

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.

Here is the rest of the quote that creationists conveniently leave out:

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.

The rest of Darwin’s chapter goes into great depth describing the full range of photoreceptor solutions in the animal kingdom, which creationists also conveniently fail to address.

Fast-forward 153 years later to the culmination of this line of argument, represented by Ivan Schwab’s outstanding book Evolution’s Witness: How Eyes Evolved.

Written By: Donald Prothero
continue to source article at skeptic.com

12 COMMENTS

  1. Dawkins lays out a very well explained, and moderately well detailed, explanation of the eye’s evolution in his Blind Watch Maker documentary (and I assume he goes into even more detail in his book by the same name).

    It is a major part of the doc, but he also goes into more general evolution explanations in the rest of it. Highly recommended.

  2. Strikingly, it was long feared, over many lifetimes, to question whether the Earth be flat under pain of even thinking it might be spherical or otherwise. The very pain of thought was taboo, on such matters. I think this illustrates well the human minds capacity to defer the unknown to exactly that: we humans really have no idea about any god whatsoever so, erm let’s insist it be god who knows everything! Um yep that’s easy, now listen up everyone – or die!!!

    With the above in mind it becomes almost comedy to mull over how exactly we look at something like the eye, and being perplexed by its complexity, arrive at a solution of an all seeing eye to which we ask no questions and empty our brains of everything they were made to do – in effect render it taboo to think or question the “all seeing eye” as explanation as to why we have eyes to see. It’s that old flat Earth “Don’t ask any questions” servitude that then demands we punish and resent those who do. This meme for ignorance is more powerful than first meets the eye (eye roll), the world over, and bully to boot!

    Funny how an invisible bully happens to be the most sophisticated explanation most people have for how we all see. Something hilarious too, about how humans even come up with such a contradiction, along with its large family of cousins, time and again!

  3.   British biologist St. George Jackson Mivart was initially a supporter
    of Darwin, but when his Catholic religion caused conflict with Thomas
    Henry Huxley in 1871, he changed to a critic. Mivart’s critique focused
    on the issue of the perfection of the human eye>/b> and how he could not
    fathom how it could have evolved by natural selection and random chance
    (a point still raised by creationists today who know nothing about
    comparative biology).

    “Perfection”!!!!!!!  If a shop selling telescopes, cameras or spectacles sold a product this inaccurate and approximate, most customers would demand their money back!

    Richard made a video explaining eye evolution in 2010:- http://richarddawkins.net/vide

    And an earlier one here:-

    http://www.ask.com/web?l=dis&a

  4. it’s a shame the eye still has this almost mystical property with regards to evolution and/or design.

    to me it’s always seemed that as humans our sense of vision is so key to our own consciousness that eye design has been elevated to a divine level. comparrisons are made with cameras that we humans have invented, and jolly tricky to invent they were too but to then project this marvel of human achievement onto the its supposed designer is rather narrow minded and anthropocentric. energy travels everywhere and all matter reacts to it in some way. eye evolution is possibly one of the most likely phenomenon to happen to any organism capable of movement.

    there’s no doubt that what our eyes seem to do is quite wonderous but most of what we credit our eyes with is actually brain function. our eyes are as animal organs go, pretty simple and not especially efficient.

    I think the historical obsession with eye complexity must stem from the limitations of what could be observed in Darwin’s and Huxly’s days.

    If you want to astound someone with the unlikely wonder of evolution, pick a cell, any cell and take a look at what’s going on

  5. Yes, it’s often never questioned as to why various eyes see differing wavelengths of the electromagnetic spectrum, and why we see only a short band of this that other eyes may see different sections of. Then also why our nervous systems feel various temperatures within, yet again, narrow bands that we only are able to live within the boundaries of. All our senses and those of various life forms, exhibit similar qualities which is why these qualities are what helped them survive the many mutations their ancestors underwent.

    What I find more interesting is the emotional congruence human insist on classifying alongside various physical characteristics of human life per se, absent the wider contexts of all life, that then makes their brains a sitting duck for feeling centric assertions. This is a science all its own! 

  6. I recently saw a very interesting documentry on colour perception. while it’s easy to attribute evolutionary pressures for differencees between species, other than colour-blindness caused by a known fault, there is a difference between wavelengths that can be percieved in different humans.

    the fascinating part was that this had nothing to do with any physiological differences but linguistic ones. a test was carried out on european subjects and those of a remote tribe who had a completely different way of describing colour. when shown a ring of blue dots that were allmost identical they were unable to spot that one of them was very clearly blue/green. However they were able to spot the difference between two blue dots that to me and anyone else in the west were identical (I’m sure someone here will remember it nad maybe find a link)

    whenever we talk of how wonderful something like sight is, the wonder should be reserved for the brain and the consciousness it supports rather than the crude hollows of jelly that cause a bit of light to converge

  7.  There clearly a significant differences between different races of humans.

    RACIAL VARIATIONS IN VISION – http://aje.oxfordjournals.org/

    As a group, the Aborigines have significantly better visual acuity than
    the Europeans. This was true
    for both monocular and binocular vision. Some
    Aborigines have acuities below the previous postulated threshold levels.
    Aborigines
    as a group also have less myopia—In particular,
    less high myopia—and less astigmatism than Europeans. The mean
    refraction
    for Aborigines is about half a diopter more
    hypermetropic than that for Europeans, although there is not an excess
    of high
    hypermetropia in Aborigines. The lack of high
    refractive errors suggests that the Aborigines may not possess the genes
    that
    cause abnormal axial lengths usually associated
    with high refractive errors in Europeans. The superior vision of the
    Aborigines
    persisted, however, when comparing groups which
    were essentially emmetropic. Therefore, It appears to be a true racial
    difference
    which is not explicable on the grounds of variation
    in refractive error but may result from finer retinal organization or
    better cerebral Integration of visual stimuli.

  8. I remember a quote from Prof. Dawkins about critics of evolution, and I think it was specifically related to the evolution of the eye that I really liked. Such critics often say that they “can’t imagine” how the eye could evolve without a designer. He made the point that just because an individual can’t understand how something is true is hardly a strong argument. But of course he said it much more eloquently. Anyone remember the exact quote? I think it was in The Blind Watchmaker but I’m travelling and for a while won’t have access to the book (this is why I buy eBooks from now on) and I want to reference it for something I’m working on. Eternal gratitude if anyone can give me the quote.

  9. Its a submission for a discussion topic which I sent in last night. Not that its a big secret but I would rather not go into the topic here. I imagine (rather hope) it will be somewhat controversial and rather than just state the idea (which is totally off topic for this thread anyway) would rather wait until my fairly detailed argument gets published as a discussion topic. If you see one from me, that’s it I’ve only submitted one.

    I ended up doing without the reference to Blind Watchmaker. I had more text than was normal for a discussion topic anyway so needed to pare it down as much as I could. I will say that my thought was to actually turn Prof. Dawkins argument against him. On a completely different topic he actually said “I can’t conceive any other explanation but that…” I think his “…” is wrong and was going to mention that he was dong on this topic exactly what the creationists do.

    Just to be clear, I admire Prof. Dawkins immensely. However, after reading his books and his philosophy on science and critical thinking I think the best way to show my respect is not to tell him how great he is but to find the very rare instances where I might be able to find a flaw in one of his arguments.

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