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Evolution: In blind cave fish, a protein change supports controversial evolution mechanism

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blind and sighted forms/Haplochromis

From Scientific American:

In the classic view of evolution, organisms undergo random genetic mutations, and nature selects for the most beneficial ones. A recent study in Science adds a twist to that theory: variability already present in a population’s genome may remain hidden in times of plenty but come unmasked in stressful situations, ready to help with adaptation.

HSP90 binds to other proteins to keep them properly folded, but under stress may allow for more variations.

Amazing, how it all “just happens”.

Abstract In the process of morphological evolution, the extent to which cryptic, preexisting variation provides a substrate for natural selection has been controversial. We provide evidence that heat shock protein 90 (HSP90) phenotypically masks standing eye-size variation in surface populations of the cavefish Astyanax mexicanus. This variation is exposed by HSP90 inhibition and can be selected for, ultimately yielding a reduced-eye phenotype even in the presence of full HSP90 activity. Raising surface fish under conditions found in caves taxes the HSP90 system, unmasking the same phenotypic variation as does direct inhibition of HSP90. These results suggest that cryptic variation played a role in the evolution of eye loss in cavefish and provide the first evidence for HSP90 as a capacitor for morphological evolution in a natural setting. –

See also: Cavefish Study Supports Controversial Evolutionary Mechanism

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41 Replies to “Evolution: In blind cave fish, a protein change supports controversial evolution mechanism

  1. 1
    Robert Byers says:

    As a creationist I love the critters who are blind in caves etc. many insects and fish etc.
    I see it as evidence of how adaptation happens quick and for some equation of need. the idea that a fish with a mutation making its eyes not work was a benefit over others seems unlikely. it happened everywhere.
    Other options are more likely. Bring them out and see if the eyes of descendents start working again.
    Its not evidence for evolution but only a result that speculation acts on.
    Its not evidence for a origin for a mutation that stops the eyes either.
    one mans mutation is anothers adaptation from another mechanism.

  2. 2
    AVS says:

    You don’t think it’s odd that these fish live in complete darkness and yet they have eyes? If I believed in the design of all organisms, I would certainly be questioning the intelligence behind this.

  3. 3
    Mung says:

    If I believed in the design of all organisms, I would certainly be questioning the intelligence behind this.

    Why? Does having an eye in some way become an immediate detriment to a being in complete darkness?

    You’ve never been in complete darkness? You did not immediately pluck out your useless and in fact detrimental eyes? Why not?

  4. 4
    Jul3s says:

    AVS, your question is bizarre considering how straight-forwardly the answer is given in the article.

    Why would you question the intelligence behind giving a design an off-switch? Your criticism is nonsensical.

  5. 5
    AVS says:

    What an excellent comparison.
    You don’t think it’s odd that an organism that spends its entire life in the dark, has eyes? If you had been designing that fish, would you have given them eyes? I don’t think I would’ve. Wouldn’t have made much sense to me. That’s all I’m saying.

  6. 6
    wallstreeter43 says:

    AVS it makes all the sense in the world and who knows, maybe one day they will be needing those eyes again and viola the switch is back on again.
    This is intelligently designing a species to help them adapt and survive best.

    But I guess u dont think thats reasonable or logical do you.
    Almost everyone else does 🙂

  7. 7
    Mung says:

    AVS, as “intelligent designer,” would have designed an eye that popped into existence as needed and popped out of existence when not needed.

    AVS, as “intelligent designer,” could predict when an eye would be needed and when an eye would not be needed and could thus design an “eye popping” mechanism that would pop eyes into and out of existence as needed.

  8. 8
    Querius says:

    There’s a difference between an intelligent designer and a magician. With an intelligent designer, we can gain an appreciation for the intelligence in the design. With a magician, we can learn only that magical things happen.

    -Q

  9. 9
    Jul3s says:

    AVS, your objection only works based on an extremely short term view of what is beneficial and what isn’t.

    You are basically saying that it would be smarter to bet that a population of fish will never ever need eyes no matter what happens to the environment over millions of years. That is not wise bet.

  10. 10
    AVS says:

    All I’m saying is that an organism that spends its entire life in the dark and does not need eyes, does not need an on or off switch for eyes. In fact they don’t need any of the genes required for correct eye development. And yet they have them. The most seamless answer to me, is that the blind populations have evolved from the sighted population, and benefit from the loss of functional eyes.
    A designer would not have given this species the blueprints for eyes if they were never going to use them would he? I don’t think I can explain it any other way.

  11. 11
    AVS says:

    Well thankfully, Jules, that is why we have this mighty designer who can “pop” eyes, according to Mung, back into the fish when they start leaving their caves.

  12. 12
    Jul3s says:

    But the *population* needs an on or off switch (which has been discovered) because sometime in the future the population might need eyes again (and it is crazy to say that in millions of years, the environment cannot ever possibly in nay way that might make eyes beneficial again). That was the point of the article which you obviously missed.

  13. 13
    Jul3s says:

    In case you are still missing the point, the blind fish evolved blindness not by random new variation but by a per-existing but ‘dormant’ variant.

  14. 14
    AVS says:

    Careful now Jules, you are making claims that are not supported by the evidence. The paper says that taxing Hsp90 activity leads to changes in the cavefish eye size. Not complete loss of the eye. Blindness in these fish is much more complicated than this single, simple on/off switch idea of yours.

  15. 15
    Jul3s says:

    That has nothing to do with what I was saying or what the article was saying.

  16. 16
    AVS says:

    What? That is exactly what the paper says.
    “heat shock protein 90 (HSP90) phenotypically masks standing eye-size variation in surface populations”
    Hsp90 hides eye size variation.
    “variation is exposed by HSP90 inhibition and can be selected for”
    They modeled the “maxing out” of Hsp90 by inhibiting it, and saw a huge increase in eye size variation. They were then able to select for smaller size eyes and pass the traits on, modeling one step of the the evolution of these fish to the blind phenotype.
    Are we reading different papers?

  17. 17
    Jul3s says:

    Changing the subject completely and discussing the complexity of the mechanism instead of the original discussion is a very obvious evasion tactic.

  18. 18
    Upright BiPed says:

    You don’t think it’s odd that these fish live in complete darkness and yet they have eyes?

    Apparently this person believes that these fish originated in caves. The comment doesn’t make sense otherwise.

  19. 19
    AVS says:

    Evasion? I only went deeper into the paper. Your argument was that there is an on/off switch for the eye. It is not that simple, though. I’m sorry that your argument hinges on a superficial understanding of the topic, but that’s what happens when a layperson tries to talk about complex science.

  20. 20
    AVS says:

    No, biped it’s pretty well understood that the species originated at the surface level and a subpopulation of the species has evolved to survive in underwater caves. Anything else to add?

  21. 21
    Upright BiPed says:

    Then it’s not “odd” that they have eyes. They are part of their genetic history.

  22. 22
    AVS says:

    What is odd is that a subpopulation of a species has eyes while another doesn’t. And yet the population that doesn’t need eyes still have the majority of the ability to grow eyes. I had said that if a designer was taking away the function of the eye, they would scrap the blueprints too. But instead we see most of the blueprints hanging around and are functional, as we would expect with evolution. I was not really talking about the article itself at first, just the species and the work that has been done on it previously.

  23. 23
    Jul3s says:

    AVS, first you play dumb and then you condescendingly claim that it isn’t that simple and pretend to know my personal history. You cannot claim to know that my argument hinges on a superficial understanding of anything because you are blindly determined to ignore every statement and make smug remarks lacking content, depth and substance.

  24. 24
    Upright BiPed says:

    So, as it turns out, their isn’t anything odd about it.

  25. 25
    AVS says:

    I read the article here on UD, then realized you ready for a decent argument and read the whole paper. That was when I understood where you got lost in the details. Its ok, it happens. =)

  26. 26
    AVS says:

    Yes, Biped, nothing is odd if you accept evolution took place. It’s when you think the blind fish was designed blind, and yet still has much of the necessary functions of sighted fish that things get odd.
    That was my point. Congratualtions

  27. 27
    Upright BiPed says:

    Yes, Biped, nothing is odd if you accept evolution took place.

    Why would I think anything else?

    It’s when you think the blind fish was designed blind

    Who thinks this? Is this not something you just invented, or does it appear on this thread?

    That was my point.

    Thanks for the clarification.

    It was a pretty weak point; apparently based on nothing of actual substance.

  28. 28
    AVS says:

    The guy who first commented was who I was originally trying to talk to. He seemed to think that the blind cavefish were “designed” blind. To which I was hoping to ask him why he thought we can still get the fish to develop an eye by just inserting a small piece of lens from a surface fish.
    Obviously things didn’t go to plan.

  29. 29
    Jon Garvey says:

    A key point is surely that evolution by natural selection cannot anticipate need – it is purely an opportunist.

    Here, though, is an example where need is apparently anticipated by a gene hanging about in the wings. Prima facie then, evolution did anticipate future need, and so the denial of that anticipation is a metaphysical choice, not a following of evidence.

    Neutral evolution, of course, gives a possible mechanism by which a protein could “turn out” to be useful without adaptive steps, but that too is simply a belief that what appears purposeful was fortuitous.

  30. 30
    Jul3s says:

    No, nobody even seemed to think that the fish was designed blind. Such extreme misunderstanding makes discussion a waste of time.

  31. 31
    AVS says:

    No, actually here they show how a change in conditions can increase the variations of a trait in a population. Natural selection can then act on this variation, which they modeled.

  32. 32
    AVS says:

    I’m pretty sure the first commenter did. And if you dont think it was designed blind then you’re the type that believes in some kind of “designed evolution”?

  33. 33
    Upright BiPed says:

    Robert Byers is a person who can start a sentence and contradict himself before he makes it to the period. I’m certainly not prepared to waste my time trying to make sense of him.

    On the other hand, Mr Byers comment does nothing to rescue the comment of yours that I quoted – by your own explanation of it.

    cheers

  34. 34
    AVS says:

    That would be because up until comment #10 I was under the impression that the blind fish still had eyes and that they were nonfunctional. Don’t tell anybody.

  35. 35
    Joe says:

    AVS:

    And if you dont think it was designed blind then you’re the type that believes in some kind of “designed evolution”?/

    So you are admitting ignorance of ID, finally. And please demonstrate how natural selection produced these fish. Start with demonstrating how you determined the mutations wer happenstance.

    Thanks.

  36. 36
    Paleysghost says:

    The fish were not “designed blind”, AVS — the eyes were “shut down” to conserve energy after the population became trapped in a dark environment(like turning off your lights on a bright sunny day), which is “logical”.

    Not to mention the fact that the eyes have not been “completely erased” from the genome, and a few adaptations and breeding (if the population is suddenly released from the darkness) will re-activate sight in the offspring.

    Reading your comments is just physically painful.

  37. 37
    Dionisio says:

    “I was blind, but now I see.”
    Was I designed to be spiritually blind? Actually, on the contrary, I believe I was designed to have spiritual sight. Blindness is just the absence of sight. God graciously had the Holy Spirit turn up my spiritual switch to ON, through a mechanism known as ‘saving faith’.

    Now, let’s switch to the biological vision. As we all know well, there’s more to biological sight than just the eyes, which are an important part of the vision system. Hence, the presence of eyes does not imply having vision. It’s a necessary but insufficient condition. The whole mechanism may be physically present, but dysfunctional (deactivated).

    The deactivation could derive from a broken or missing component. But also could be due to a switch being off.

    As we humbly approach the big data coming out of research, we may look forward with great anticipation to more light being shed on these mysterious issues. We crave for results. The more information we have, the clearer we see the elaborate choreographies and orchestrations hidden under the visible traits and physiology. In awe we contemplate all this and sing hallelujah.

  38. 38
    lifepsy says:

    Eye expression is stimulated by light levels in the environment… there was a bunch of phenotypic plasticity experiments done on them a couple years ago.

    Just another creature with pre-programmed variability to deal with multiple environments. Darwinian evolution again is just inessential baggage trying to shoehorn its way into the article.

  39. 39
    SteRusJon says:

    AVS (and others),

    I will come to Mr Byers defense even though I do not espouse many of his views. Mr. Byers is, I am sure, Canadian. I strongly suspect he is French Canadian. I suspect that English is his second language and I applaud his effort to express his views in this English forum. Since his English is light years ahead of my French, I refuse to look down my nose at his efforts. His thoughts, very likely, are more coherent when expressed in French. Whether you agree with them or not is irrelevant to the expression/comprehension issue.

    Now, I realize you may be unaware of all this. But it is obvious that his posts can be difficult to parse. Whatever the reason for that, it behooves the reader to be particular when reading them. All the more so, if they are going to be used as a spring board for a reply.

    I cannot see, unless you wish to read uncharitably, how you conclude that Mr. Byers thinks that cave fish were created blind. In the post Mr. Byers uses the following three phrases:

    “evidence of how adaptation happens quick”

    “see if the eyes of descendents start working again”

    “one mans mutation is anothers adaptation from another” mechanism.

    The first and last phrases contain the word “adaptation” and the middle one has the word “again”. These words strongly suggest that he believes that the blind fish are descended from fish with fully functional eyes.

    AVS, to think that an important tenet of ID is the special creation of species with dysfunctional subsystems because of the first post in this thread indicates your need to joust with straw men. Furthermore, it shows to me a lack of charity on your part.

    To others. If the shoe fits, wear it.

    Stephen

  40. 40
    seventrees says:

    Greetings.

    SteRusJon at 39:

    I will come to Mr Byers defense even though I do not espouse many of his views. Mr. Byers is, I am sure, Canadian. I strongly suspect he is French Canadian. I suspect that English is his second language and I applaud his effort to express his views in this English forum.

    C’est vrai, M. Robert Byers? I really hope it is the case.

  41. 41
    Robert Byers says:

    AVS
    I’m not French Canadian. I’m Canadian. I’ll try to improve my lingua populi.
    I’m YEC and believe the fall came and destroyed biology. In its place is a distorted biology that wotks just to keep life alive. So YEC accept adaptations, like in people colours/shapes, as long as critter stays in kind.
    I love cave blind creatures as it proves they went blind only upon entering the cave. It proves biological mechanisms to all.
    Then what mechanism?
    Its so coomon, and more common in the past, for such creatures to be found thats it likely its a innate mechanism and not from selection even in acceptable doses from creationists.
    Its unlikely its selection on a few traits. Why should a blind one do better then a blinded seeing one constantly.
    Possibly one could argue the winning/surviving blind ones work smarter in darker areas and the sighted ones were still grasping at lighter areas and the blind ones prevailed having more chance for food.
    Yet I doubt it. I think undiscovered mechanisms are affecting biology and bringing needed results.
    They are good clues for everyone however.

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