Blind cave fish see the light

_{Mark

January 11, 2008

Intelligent Design}

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Two blind fish can make sighted offspring.

“The offspring of crossbred blind cave fish see like their surface-dwelling cousins.

The results in Current Biology 1, show that the two populations took different evolutionary paths to blindness.

“We’ve basically shown that these different populations have converged upon the same outward appearance independently, and that they use different genes to do it”, says Richard Borowsky of New York University.”

This is the type of thing that RM and NS can do. I would say that they lose different genes to become blind, not use different genes.

Comments

jerry: "Something was operative in the cave environment to create blind fish. I understand how a mutation can create blindness but why would that mutation then become dominant. I can think of some reasons but they are just speculations." I would disagree. I think it is a much more passive thing. Blind offspring from sighted parents likely occur equally as often for fish not in caves as for fish in caves, but for fish in caves this is not a disadvantage, so they are not eliminated. The genetic entropy increases without limit w.r.t. visual systems until it is impaired to the point of non-functionality.SCheesman_{January 11, 2008
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Read the fine print. The picture captions & title are misleading. Some yellow journalism there. Normal sight was not restored but rather partial sight at best, sight that quickly deteriorated no less, in a fraction of the offspring. I question what controls were used in this experiment but don't have access to the original article.
in the most successful pairing, 40% of hybrid fry could see.
...
They then tracked eye movements while the fish were presented with a rotating pinstripe pattern. A number of the hybrids could track the pattern with their eyes — at least for a while. The young fishes' vision deteriorated with age.
As I said elsewhere this is not surprising at all and can be easily explained by Mendel's 6 principles of inheritance coupled with RM+NS and bit of observation subsequent to Mendel. It shouldn't be surprising at all that something as complex as the eye has a complex gene network behind it that can be catastrophically damaged anywhere in a large number of genes. Random mutation introduced errors in some genes in visual cascade. In the separate populations different genes were damaged but the result was the same - total loss of vision. Because there is no need at all for vision in total darkness natural selection didn't act to cull the mutants. It explains why the fish became blind in the first place - genetic entropy on steroids so to speak. Mendel didn't know any of the above. As Mendel discovered, genes (he called them particles because they didn't tend to blend like a fluid as Darwin believed) travel in pairs in diploid organisms. Germ cells have the pairs split apart. When sexual recombination occurs one gene from each parent recombine to form a new pair. If the genes aren't identical one of the pair may be dominant while the other is recessive in the offspring. In the blind fish experiment the parents had some undamaged, or at least not catastrophically damaged, genes in the set of genes needed for visual function. The two populations had different sets of undamaged genes but neither had a complete set of undamaged genes. In the hybrid offspring there would be gene pairs in the visual array with one damaged and one undamaged gene (heterozygous for the damage) where in the parents the gene pair was two damaged genes (homozygous for the damage). As learned through observation subsequent to Mendel a damaged gene is usually a recessive gene or, conversely, an undamaged gene is usually dominant. So in the hybrids some of the visual system was restored in the first generation because where the damage was homozygous in the parent it became heterozygous in the offspring with the undamaged gene in the pair being preferentially dominant. What would be an interesting follow-up experiment is to selectively breed hybrids with partial vision to see if vision was eventually completely restored which would be conclusive evidence that a complete set of functional vision-related genes could be cobbled together from the two isolated populations' genomes. However it's only mildly interesting because complete or incomplete would not be surprising in any significant way nor would it add to our general knowledge of genetics. It would add only to knowledge about the two specific populations of blind fish. As Jerry said this doesn't really speak to ID one way or another. The neo-darwinian theory of evolution is essentially correct when applied in the short term - "microevolution" if you will. It's only when the theory is extrapolated to the long term (macroevolution) that it becomes incredible - i.e. the hypothesis that macroevolution is just a whole lot of microevolution over deep time. Processes usually don't scale to infinity in a linear manner which is something that engineers are acutely aware of but biologists tend to ignore in the case of RM+NS. What they are doing is like concluding that you can pile rocks high enough to reach the moon based upon the observation that you can pile rocks high enough to reach the clouds (a mountain). The process of rock piling doesn't scale that far in a linear manner before the underlying principle becomes non-linear. In another example, transistors can be linearly scaled down in size through quite a range and this is well explained by classical mechanics but there is a point where quantum mechanical effects overwhelm the classical and the size no longer scales down linearly due to it. Biologists are making an unjustified presumption that RM+NS scales linearly from microevolution to macroevolution when in fact the empirical evidence points to a much narrower bound where the scale remains linear. DaveScot_{January 11, 2008
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Is this similar to the hairless chiuaua or finch beaks? That is, once you take the hairless chiuaua or the finch out of the environment that was placing a tax on the system, the organism reverts back to its original form.ajl_{January 11, 2008
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Something was operative in the cave environment to create blind fish. I understand how a mutation can create blindness but why would that mutation then become dominant. I can think of some reasons but they are just speculations. I have heard about blind fish before in caves but no details. Is it just one cave or are there several caves independent of each other that have blind fish? Are there caves that have fish with eyesight? Examples like this are why I believe ID should include the modern synthesis as part of its basic approach to evolution. NDE clearly makes some changes to genomes and many of these changes help the organism to adapt and persist. However, it is limited. It is why I consider this type of research as ID research because it is part of the paradigm that Behe is preaching. Namely, the modern synthesis works but is limited as pointed out in the Edge of Evolution. So any research that shows that NDE does not produce any novelty over time is ID research whether the researcher says it is or not.jerry_{January 11, 2008
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Note that they became blind in the first place because natural selection was NOT operative in the cave environment w.r.t. blind individuals, so the harmful mutations were able to survive when normally they would have been eliminated -- demonstrating that the true and limited role of natural selection is to preserve information from loss by harmful mutation, not create it.SCheesman_{January 11, 2008
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idnet.com.au: "This is the type of thing that RM and NS can do. I would say that they lose different genes to become blind, not use different genes." I think you are quite correct; Likely both lines of blind fish became blind due to the harmful mutation and loss of separate, but vital parts of the same system responsible for the production of sight. Breeding combined and restored the "missing" genes to allow the original system to function as designed. Net gain in information from the original situation? Zero.SCheesman_{January 11, 2008
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