How can evolution explain body symmetry?

The New YorkerI think the analogy the author uses to describe a direct route to an irreducibly complex system is quite humorous. Our first random mutation built us a simple 600$ Garmin and a 12 billion dollar satellite system. The next random mutation will build us a computer that can drive our vehicle for us. After all, "no one would be surprised" by that. Now if the molecules all came together in the right fashion, and this new mutation appeared by itself (hey, he made the analogy), I might be surprised, but the author is right, I certainly wasn't surprised to see this. Ask yourself why? Why does it seem LOGICAL to link a location finding device to a location changing device? I would argue it's because you're intelligent. Of course, I'm not smart enough to do it myself, but I certainly conceived of the idea long before this author published his article. H. Allen Orr seems completely unphased by the fact that his first example of a direct path to an irreducibly complex system involves quite a bit of guiding intellect. He goes from saying "We add new parts like global-positioning systems to cars not because they’re necessary but because they’re nice" to saying "It’s important to see that this process is thoroughly Darwinian" three sentences later. I'm sorry but that's total crap (and only takes like 10 seconds to read). Our adding of anything at all to almost any other thing in industry is almost NEVER Darwinian. It is DESIGNED, quite painstakingly I might add, to make more money.Perhaps it's curious to you that he didn't use an example from nature, you know, since they're obviously everywhere. Instead we get a double cop out in the next analogy (also not from nature). We're not sure why, but we know this "bustling urban street" evolved incrementally (I think partly because that's the point of the analogy and because we'll eliminate "Urban Planners" later, in case you know what those are or have a tyrannical one running your city... like I do). Now firstly, although we know it evolved store by store, each store has so affected the other, that we lost a large part of the evidence as to which came first. Oh, and secondly, it's not irreducibly complex. Remove one shop, and the other shops don't cease to function.It's not like I can't conceive of what he's trying to describe, but it's hard to ignore the elements of intelligence and design he chose to include as his analogies. You can't convince me intelligent design is "junk science" if you rely upon it for your analogies to work. At best you would have junk analogies.

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Human design is a process of trial and error, and passing on successful approaches to students. In this respect it is exactly analogous not to divine creation, but to natural selection.

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No, natural selection does not generate information, it reduces it...by definition. It does not remember what didn't work, nor does it develop a database of "successful approaches" to mutation. Only a successful RESULT is passed on. The DNA does not learn HOW to produce the mutations it might "want". The author's analogy fails because it is PRECISELY an example of a intelligently and PURPOSEFULLY designed system.

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Each time something is thought that might work, it relies either on past experience, that is, trial and error, or some leap, large or small, that is not guaranteed to be successful until it is tried out.

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Again, natural selection does not make anything new and the random mutations it can select from are not incrementally more successful due to any type of "past experience" or something that is "thought that might work".Or perhaps I have it wrong and DNA is self aware.

I did read that entire article, but it only talks about the kidney's abilities to regulate salt and frames the entire issue of it's usefulness in those terms which seems terribly close minded. I don't think the post it was in response to claimed that the kidney was irreducibly complex. I only found that term in the response.But his claims of marine life evolving back and forth between fresh water and salt water got me wondering. If I could identify distinctly isolated bodies of freshwater would I find any vertebrate species in both that appeared (or were by genotype) nearly identical? I was thinking along the lines of, "If God thought like me and decided that fish X was kind of neat, would he only place it in interconnected bodies of freshwater (or those on the same continent or continental divide)" in creation mode. In evolution mode, I was thinking even if they were transplanted long ago somehow, they would certainly have drifted far enough apart to have lost the capability to breed. Over subsequent millennia (enough to make their habitats clearly isolated) they would certainly have evolved as to be almost unrecognizable by phenotype and comparable by genotype only to a common ancestor. I think what I found might turn the talk back towards things like how certain environments might select certain shapes. shorthened the link. PLEASE, use peek to see how it's donewhich referenceshttp://faculty.evansville.edu/be6/b4805/ps2s05/Rundle.pdfThe second article seems to describe "ecomorphs" as some sort of archetypal uber species that all similar niches will eventually be filled in with.... to such a degree of similarity that they can interbreed....even though their DNA is quite different and does not point to a common ancestor.As a layman I am quite lost at this point. Developing all the right mutations, in (mostly) the right order, with no incompatible or disqualifying intermediate beneficial mutations (which would deselect all the other candidates while simultaneously cursing incremental progress toward the perfect "ecomorph" ---> square one) seems to move the debate back to cosmology and the time window we've had. If regular evolution toward a species that is "good enough" to survive takes hundreds of millions of years, how long does it take to have a "good enough" attempt cross over to become a "great" attempt without diverging. Then again from those "great attempts" that don't diverge, how long does it take to evolve into an "almost perfect" attempt without diverging? What about getting from there to a "completely perfect attempt to the extent that it can reproduce with separately evolved ecomophs and looks almost identical" ... times at least 2 (since the archetype is defined by the niche not simply the existence of the other ecomorph).As for flagellum, are there any specific rebuttals to this rebuttal?
http://www.designinference.com/...003.02.Miller_Response.htmI have read some more recent but general rebuttals of IC but I can't find anything that deals with the specific claims of this piece (specifically sections 4 and 6). I'm sure you have some ready so I thought I'd save myself some time by asking.Seeing as you've had many classes in biochemistry, genetics, and biophysics, I would be inclined to trust evidence you provide, but it's hard for me to settle for "it's wrong, because it's wrong"This message has been edited by AdminJar, 07-18-2005 06:27 PM

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Sorry our survey said that "hence we refer to the two phenotypes as ecomorphs."

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The first part of the sentence which you did not quote reads, "Thus, neither the Benthics nor the Limnetics from different lakes are monophyletic; hence..." The "Thus" refers to the rest of the paragraph which provides the DNA evidence. They are comparing the DNA across subspecies lines and saying that these sticklebacks diverged from each other independently each time and that they are not related along subspecies lines. This takes the position that similar niches have some sort of archetypal form (which logically speaking they would) and that evolution has had time to reach it in EACH instance INDEPENDANTLY, and at the SAME TIME! In this instance they are speaking of resource partitioning causing a replication of two almost identical subspecies of stickleback across geographically isolated habitats. I find that preposterous.

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Actually all of the populations studied appear able to interbreed

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My surprise was not that the Benthics and Limnetics could breed with each other. Their constant contact and procreation has helped them retain this capability. The surprise (to my evolutionary side) is that given a marine stickleback as our hypothetical ancestor, that ONLY the new traits of the Limnetic and Benthic in niche X can be considered to offer ANY selective advantage to the species to such a degree that natural selection will discard (by some as of yet untold mechanism) ANY OTHER divergent beneficial mutations, in favor of retaining these! Common, that's the point of the whole article. Evolutionists are forced into this position (which the authors describe in the first and second sentences of the second paragraph) no matter what ancestor they choose to claim these fish came from. Not only in this case did they branch into two subspecies to share resources in EACH lake, each subspecies are basically the SAME, AND in the SAME STAGE (it's a separate improbability)! In fact, they are so similar, that they can mate along these subspecies lines, and PREFER TO! Don't you realize what an incredible position that is? Don't you see how that radically compounds the improbabilities? It imbues natural selection with "forecasting" powers by claiming that advantages that would diverge them from the niche archetype are discarded in favor of "holding out" for "the" perfect advantage AND that these "random" mutations seem to be coming according to some timetable! I think you came up with the common term for this.

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So in fact there is absolutely no indication that these populations don't share a common ancestor and every indication that they all derive from a genetically diverse ancestral population of marine threespine sticklebacks.

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If you took "common ancestor" to mean a common ancestor to all the sticklebacks in the study, then that is beside the point. The authors do actually suggest that as a side note (which they don't footnote - probably because it is beside the point, or maybe because they just dreamed it up... I don't really care). The importance of the DNA study was to show that the split into subspecies occurred AFTER the presumed geographic isolation of these sticklebacks from each other. They're saying that these fish are not ancestors along subspecies lines. It's what makes their existence so amazing to you.But if you want instead to get away from discussing parallel evolution (I would if I were you) and talk about lineage, I'll grant you one thing. If someone else provides enough evidence to convince me that parallel evolution is possible to the extent that it explains the above examples (and quite a few others I'm finding) of parallel speciation (privately or in another thread), then I will grant you that these sticklebacks came from whatever animal you claim. I'm not being cute about that either. My evolution side says that, if this type of parallel evolution is true for a given niche then the existence of that niche's archetype in the SAME STAGE across isolated locations DOES indicate a common ancestor. Of course given the newfound powers of RMNS, if the relatives are in DIFFERENT stages of progression towards nirvana across these habitats, then they could have evolved from entirely different species.Now I can bring this back to body symmetry. If parallel evolution is such a powerful force, what is common among the niches of organisms with the same types of symmetry? This could be an answer for evolutionists as to why this symmetry exists along various lineages.edited for spelling.This message has been edited by teratogenome, 07-19-2005 03:47 AM

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if sexual selection on morphology plays any part in reinforcing the sympatric speciation then of course the similar ecomorphs are more likely to mate with those sharing their morphological phenotype

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I'm focusing on the fact that they have shared morphological phenotypes that evolved separately. Once given that they look more alike and eat the same food, I'm not surprised they also prefer to mate. I'm trying to get you to ask "how did we get here".

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OK, so show me anywhere where it shows that the same "random" mutations are responsible for these phenotypes in all cases.

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The improbability lies in acquiring all (or enough to be distinctly sexually selected for) the same phenotypes by whatever mutations caused them.

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That would almost be a worthwhile point, if it wasn't for the fact that the limnetic x benthic crosses from different lakes actually mate as well if not better than those from the same lake.

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I was only making the point that they preferred to breed along subspecies lines to illustrate just how distinctly similar their phenotypes are to each other. What I said was intended to delineate what I was not focusing on (Limnetics choosing Benthics and vice versa).

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Any scintilla of support for that that you can find anywhere in the paper?

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They write, "The genetic evidence indicates that the Benthic-Limnetic pairs from three lakes (Priest, Paxton, and Enos Lakes) are derived independently of one another". If evolution must be true, and these fish do exist, and their DNA points away from one common Benthic or Limnetic, then in three separate cases parallel evolution selected phenotypes so similar to each other that we call the Benthics in every lake Benthics, and the Limnetics Limnetics. And the fish appear to agree with our naming scheme. If beneficial divergent mutations had been selected, then the species would have diverged. Either agree with my logic or tell me that no beneficial divergent mutations occurred (or tell me they weren't selected for somehow).

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You can say that there hasn't been sufficient drift or directional selection to lead to speciation between similar ecomorphs in differing lakes, but that is all.

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I'm not debating that. Although by the definition of an ecomorph, there shouldn't be any more directional selection until the selection pressures of the niche change. What I've been trying to say is that it seems highly unlikely that drift and directional selection would lead to 3 cases of nearly identical speciation in the first place as the authors claimed.

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Since the reproductive isolation is only pre-mating, as far as we can see, and given the short time period involved there is no reason to assume any large scale or widespread genetic changes have occurred. I don't think you could say anything at all about the relative beneficence of whatever genetic variations might exist between the populations from differing lakes

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I'm not making that argument either. I'm not talking about beneficial variations that might currently exist between different lakes (a random distribution of which one might expect - which would also point away from parallel evolution). I'm talking about having the same beneficial mutations selected for previously to such a degree that it results in a nearly identical divergence into the same subspecies in all three cases. The changes that have occurred (if parallel evolution caused it) are at least large scale enough to have been naturally selected for and distinct enough for the fish and the researchers to recognize clearly now.

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No, it imbues natural selection only with the ability to fit square pegs in square holes...

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You're kidding me? Assuming, for arguments sake, that it isn't absurd to claim the ability to compare all the relevant environmental variables that affect selection within a given niche, you now want to assume that these PRECISE phenotypes occurred without interference from other selectable divergent phenotypes and at a minimum of 3 times, to the same species in each case (Limnetics kept looking more like their distant Limnetic cousins even assuming the Benthics never changed)?? Even if you can claim that natural selection is selecting for precisely the same traits in each habitat, you also want to claim that random mutation is now ordered to not produce any beneficial mutations that would cause entirely different looking but well suited sticklebacks?

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and since the original populations can be expected to have had a reasonably similar stock of genetic variance to work on to begin with

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So because they must have had the same gene pool at one time, this so limits the number of possible beneficial mutations... that they must all be the same to this degree now?

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we don't know that these all occurred at the same time or over the same time period only that they occurred within a rather broad window

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So 10,000 years is now a "broad window" in evolutionary time? We've gone from millions of years to get from x to "good enough" to less than 10,000 years to get from x to the almighty ecomorph?

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Why would it be an answer in any way preferable to that of a common bilateral ancestor?

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Why be so constrained? It's just fitting square pegs into square holes after all right?I was going to say that balanced appendages and opposable muscular forces might be something selected for by gravity and angular momentum. Then I was wondering what kind of organism alive right now might be better off with a Siamese twin.