You’re fantasizing. I’m not embarrassed in the least because I know I have the best case regarding this dispute. But at least this dispute has allowed me to see that we can always count on Tim’s bluster to hide it’s embarrassment when he faces plant.
I’m just gonna leave this here…
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You should be.
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…and 99% of scientists that actually study these matters have been duped! Definitely that’s the most likely scenario. Definitely.
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You should be very embarrassed with your continual demonstrations of scientific ineptitude. I suppose Creationists as a rule lack the self awareness to be embarrassed by their failures.
I already explained to you back mutations and gave a real world example which you of course completely dodged. But according to you and Behe such things are impossible. 
If you think that with his irrelevant peppered moth example Tim has demonstrated that my skepticism regarding polar bear reversion was unfounded, then I am sorry to tell you that you don’t understand the subject either.
What magic barrier makes it impossible for a polar bear to have a mutation producing brown fur? You keep forgetting to tell us.
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Just going to leave this here.
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Your peppered moth exemple was completely off the mark.
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Funny that everyone else watched it nail your silly polar bear claim to the wall. 
What magic barrier makes it impossible for a polar bear to have a mutation producing brown fur? You keep forgetting to tell us.
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To emphasize Tim’s post, perhaps you could address my earlier question.
If mutations in the polar bear changed the polar bear gene for coat color so that it is identical to the brown bear gene, would the polar bear have brown fur?
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It doesn’t even have to be identical. As Argon pointed out above a suppressor mutation can also restore the original functionality to a gene.
A suppressor mutation is a second mutation that alleviates or reverts the phenotypic effects of an already existing mutation in a process defined synthetic rescue. Genetic suppression therefore restores the phenotype seen prior to the original background mutation.[1] Suppressor mutations are useful for identifying new genetic sites which affect a biological process of interest. They also provide evidence between functionally interacting molecules and intersecting biological pathways.[2]
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Okay, let me explain you.
The polar bear has evolved over time from the common brown bear by changing its fur colour to white, the ideal colour to blend in with its ice-covered surroundings. With new data an international research team now documents that the separation from the brown bear into an independent species has gone very quickly.
It is believed that a long time ago (maybe 500 000 years ago), the brown bear migrated to the north during a warmer climate period and when a cold period subsequently set in, a group of brown bears may have become isolated and therefore forced to quickly adapt to the new colder conditions. One of this adaptation was to evolve a white color in place of the original fur color, which allowed the animal to blend in with its ice-covered surroundings. At the molecular level, it is believed that this change toward the white phenotype occurred through some degrading mutations within the LYST gene that code for a protein associated with pigmentation. IOW, the polar bear display its white color because a long time ago it has adjusted to its environment by degrading a gene, ie., the LYST gene. The important thing here is to note that in its white environment, the animal is better off without a functional LYST gene than with a functional one. So in this situation, what would prevent the accumulation of other degrading mutations within the LYST gene of polar bears? Nothing of course. And as a result, one would expect the gene to harbor now several other degrading mutations. And this is the case actually, since a recent study found that the LYST gene in polar bear contain seven missence substitutions that, according to the authors, are predicted to dramatically suppress melanin production and transport, causing the lack of pigment in polar bear. Now, given this situation, what is the chance that the multi mutated non functional LYST gene in polar bear can revert to a functional version? The answer is nearly zero.
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I have to say that you guys are hammering on @Giltil for the wrong reasons. The specific example Tim brought up is not an example of a mutational reversion.
The bright moth allele persisted at a low population frequency in the peppered moth population during the industrial revolution(it wasn’t wiped out), and when eventually measures were taken against pollution and the environment changed, the bright allele became beneficial again.
So while the ancestral allele reverted to it’s pre-industrial revolution frequency, it did not do so by a back mutation. While mutational reversion can and does happen, this is just not an example of that.
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That doesn’t change the fact that reversion mutations can happen. There is also the possibility that mutations to other genes can make up for the loss in function (if there is selective pressure for brown fur) since melanin production is dependent on many different genes.
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For big animals like polar bears (small population size and generation rate, few offsprings), reversion and fixation of a specific non beneficial mutation would be a very rare event. But reversion and fixation of two non beneficial mutations would be so rare as to be practically impossible.
If suppression of melanin production is adaptive in polar bear, it is likely that some other genes on which depend melanin production have also accumulated degrading mutations in that species.
Let me explain it to you.
You expressed a belief this couldn’t happen
Evolution has no requirement to follow the exact mutational path in reverse to achieve the phenotypical function, in this case brown fur color. You seem to think there is only one very specific configuration of gene to produce the color.
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I didn’t offer it as an example of a reverse mutation. Just as a counter to Gil’s belief polar bears could never reacquire a brown coat through RV+NS.
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So? Your claim is like looking at a winning lottery number then demanding the random number generator produce the identical number the next week or else the first winning number was “designed” i.e. rigged.
It’s really sad you don’t understand the basic scientific concepts Behe is falsely twisting as evidence for “design”.
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Fixation of neutral mutations happens in every generation. The fixation rate is equal to the mutation rate, so about 50 to 100 neurtral mutations are fixed in each human generation. I would think that the mutation rate in polar bears is about the same.
Not if those genes serve multiple functions.
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