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Author | Topic: Behe's Irreducible Complexity Is Refuted | |||||||||||||||||||||||
NosyNed Member Posts: 9004 From: Canada Joined: |
No, I'm not saying that. I am saying that it is IRRELEVANT whether or not loss of function occurs when one of the ossicles is removed because the system is not IC according to Behe's statements. Is this definition the Hambre gave earliy correct?
quote: How is the middle ear not IC? What would it have to be like to be IC if you think it is not?
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DNAunion Inactive Member |
quote: quote: That definition is correct. But as with many/most concepts, a one-sentence definition doesn't say it all. After all, if that one sentence contained everything Behe wanted to say about IC, he wouldn't have written a book. In his book, Behe goes on to explain things more, such as what he does NOT means by a single system (an integrated system of systems doesn't count) as well as giving a better idea of what he means by parts.
quote: Okay, looks like you guys are finally settling on the middle ear (and not the whole hearing system) as the system under consideration. Let's stick with that. In this thread, several functions have been mentioned for the ossicles. But as I pointed out earlier, mere amplification is not what most people have mentioned. So I propose that we all accept transmission of force from the tympanic membrane to the oval window as being the function of the ossicles. So... SYSTEM = ossiclesFUNCTION = transmission of force from tympanic membrane to oval window All agreed?
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NosyNed Member Posts: 9004 From: Canada Joined: |
No, I don't agree on "the" function. That is being a bit silly. The ossicle perform more than one necessary function. If the hearing would not work without those functions why is one of them 'the' function? Why even worry about it actually?
The ossicles perform amplification, attenuation, transmission and impdedance matching. I suppose if one of them is "the" function it would be transmission. If amplification, attenuation or impdendence matching weren't working some volumes of some frequencies would still be heard. If transmission isn't working there is no hearing (or at least very, very little). But for now, for the sake of argument, ok, 'the' function is whatever you want it to be.
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Mammuthus Member (Idle past 6503 days) Posts: 3085 From: Munich, Germany Joined: |
However, knocking out actin makes for some pretty nasty mutants...also major or minor component is rather arbitrary. If knocking out a gene lowers fitness (even if the organism survives) it is still a major component in its pathway.
Cell Struct Funct. 1998 Oct;23(5):273-81. Related Articles, Links Recovery of flagellar inner-arm dynein and the fertilization tubule in Chlamydomonas ida5 mutant by transformation with actin genes. Ohara A, Kato-Minoura T, Kamiya R, Hirono M. Department of Biological Sciences, Graduate School of Science, University of Tokyo, Japan. The ida5 mutant of Chlamydomonas, first isolated as a mutant lacking a subset of axonemal inner-arm dyneins, has recently been shown to lack conventional actin owing to a serious mutation in its gene. It lacks inner-arm dyneins probably because actin is an essential subunit for their assembly. In addition, male gametes of ida5 are unable to produce the fertilization tubule, a structure that contains a core of actin filament bundles. To establish that those observed deficiencies are solely attributable to the loss of actin, and to provide a basis for future studies on the actin function in this organism, we examined in this study whether transformation of this mutant with cloned actin genes can rescue the mutant phenotypes. Cotransformation of the double mutant ida5arg2 with the wild-type actin gene and arginino-succinate lyase gene that suppresses the arg2 mutation yielded several transformants that displayed increased motility. All of them were found to have acquired the introduced actin gene in the genome and the product actin in the flagella, and regained the missing inner-arm dyneins and wild-type motility. In addition, most transformants also became able to grow the fertilization tubule when mating reaction was induced. In addition to the wild-type actin gene, we also used a chimeric actin gene in which the N-terminal 12 amino-acid sequence of Chlamydomonas actin was replaced by that of the greatly divergent Tetrahymena actin. Transformants with this gene also resulted in recovery of inner-arm dynein and 70-80% of the wild-type level of motility. These results established that the lack of inner-arm dynein and the fertilization tubule in ida5 are consequences of its loss of conventional actin. Furthermore, they demonstrate that Chlamydomonas offers an excellent experimental system with which to study the structure-function relationship of actin by means of mutant analysis.
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MrHambre Member (Idle past 1421 days) Posts: 1495 From: Framingham, MA, USA Joined: |
NosyNed writes: Ned, it may fit the definition of 'irreducibly complex' but it doesn't suit Behe's purposes. That's what the problem is. quote:How is the middle ear not IC? What would it have to be like to be IC if you think it is not? What Behe and his acolytes are trying to say is that certain molecular machines are essentially different from others, on no other basis than this arguable (to say the least) notion of 'irreducible complexity.' Therefore the blood clotting cascade, say, is less like the (supposedly non-'IC') hemoglobin molecule and more like a mousetrap or a motorcycle. The bacterial flagellum is less like a type-III secretory system and more like an outboard motor. Darwinism basically denies this sort of nonsense, and declares that molecular machines are just like all biological structures: the product of billions of years of variation and selection. regards,Esteban Hambre
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DNAunion Inactive Member |
quote: quote: See, this is why people need to read Behe’s BOOK instead of just his DEFINITION! Behe spends some time discussing MINIMAL FUNCTION. Here, that concept can help us nail down what the function of the system under consideration is. What could be lost and yet have the system still retain minimal function? Remember, Behe’s argument rests on what is REQUIRED, not on everything that is there. If the ossicles didn’t provide any amplification for the signal, would minimal function be retained? Yes. So amplification is NOT the function of the ossicles (it’s an additional, accessory function that is not required from minimal function). If the ossicles didn’t transmit force from the tympanic membrane to the oval window, would minimal function be retained? No. So transmission of force from the tympanic membrane to the oval window should be considered the function of the ossicles.
quote: Sounds pretty good to me. Note that amplification would still exist without any contribution in amplification from the ossicles themselves due to the differences in size and mass of the tympanic membrane and the oval window.
quote: Sorry, not good enough. That leaves the possibility of "moving the goal post" later. Either you — plural, mind you - actually accept that the function of the ossicles is transmission of force from the tympanic membrane to the oval window (and the debate progresses) or you don’t (and the debate is at a standstill). [This message has been edited by DNAunion, 03-10-2004]
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DNAunion Inactive Member |
quote: No, it's not. Lowered fitness indicates a reduction in system function, NOT loss of minimal function. If minimal function is retained, the system is still operational and the "missing part" is not a required part.
quote: The first sentence indicates that ONLY A SUBSET of the axonemal inner-arm dyneins is lacking: NOT ALL OF THEM. Some inner-arm dyneins were present even when actin was not. (The second sentence is less clear). Furthermore, the following from the abstract indicates that minimal function was retained in the absence of actin since the reintroduction of actin merely increased motility (i.e., they had motility in the absence of actin, but adding actin increased it).
quote: [This message has been edited by DNAunion, 03-10-2004]
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Mammuthus Member (Idle past 6503 days) Posts: 3085 From: Munich, Germany Joined: |
quote: Then you clearly must not consider any of the various muscular dystrophies as a result of mutations in various parts of the dystrophin, utrophin etc. complex to be particularly important either though they almost universally severely impair motility of those afflicted and ultimately result in death. In any case, the lowered fitness of the actin mutants would remove those individuals from the population if not sustained by the artificial environment of the lab..thus it is still a critical function. They would not have been observed as mutants were it not for the impaired function. If you chose to view only those mutants that completely ablate a function as critical then this is a fairly esoteric view of mutation. In any case, your original point was that using textbooks you could not find references of any significant involvement of actin in cilia or flagella and this is clearly wrong.
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NosyNed Member Posts: 9004 From: Canada Joined: |
Ok it is transmission. With an ossicle removed the hearing remaining by bone conduction is so very minimal that the individual is deaf.
added by edit I don't think there would be any amplification with an ossicle removed. The middle ear is air filled. I'd bet that there would be effectively no vibration transmitted through the air to the fluid of the middle ear. [This message has been edited by NosyNed, 03-10-2004]
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Loudmouth Inactive Member |
DNAUnion,
Since I started the thread, I will take the initiative and lay it out for you. IC system: Mammalian middle ear ossicles (stapes, malleus, and incus). Function: Transfer soundwaves from the outer tympanum to the oval window of the inner ear. Argument for system being IC: Removal of just one unit (ossicle) will abolish the function of the whole system, sound waves will not transfer from the outer tympanum to the oval window of the inner ear. You claim that Behe excludes macroscopic IC systems. I would like a reference for this. Again, this is Behe's definition of IC from this page:
In 1996, the Free Press published a book by Lehigh University biochemist and intelligent design advocate Michael Behe called Darwin's Black Box: The Biochemical Challenge to Evolution. The book's central thesis is that many biological systems are "irreducibly complex" at the molecular level. Behe gives the following definition of irreducible complexity: "By irreducibly complex I mean a single system composed of several well-matched, interacting parts that contribute to the basic function, wherein the removal of any one of the parts causes the system to effectively cease functioning. An irreducibly complex system cannot be produced directly (that is, by continuously improving the initial function, which continues to work by the same mechanism) by slight, successive modifications of a precursor system, because any precursor to an irreducibly complex system that is missing a part is by definition nonfunctional. An irreducibly complex biological system, if there is such a thing, would be a powerful challenge to Darwinian evolution." (p. 39) I will concede that the intro to the Behe quote does say "at the molecular level". However, the definition itself does not exclude macroscopic IC systems. You do have a point that Behe meant for his definition to apply only to molecular systems. However, the evolutionary pathways that have been hypothesized for creating molecular IC systems are the same ones evidenced in macroscopic IC systems. For Behe to claim that such indirect pathways are possible but inadequate he must first have 2 things. 1. The complete history of how that molecular IC system came about. Behe must show how each step in the actual development of the current day IC system were such as to exclude evolutionary pathways. For example, he must show the step by step development of the bacterial flagella. The observed complete history, not Behe's just so stories. 2. Behe must show how indirect evolutionary pathways that resulted in macroscopic/skeletal IC systems do not apply to molecular IC systems. He says that co-aptation is not an option for molecular IC systems, but this seems to be an ad hoc hypothesis used to exclude counter-evidence. His logic for excluding indirect evolutionary pathways must be based on evidence, not his own incredulity. Really, there is nothing to refute except Behe's own incredulity of possible indirect evolutionary pathways. I guess the only way to refute Behe's IC via ID hypothesis is to show that Behe does believe that indirect pathways can develop molecular IC systems. I refuted the notion that indirect evolutionary pathways can develop IC systems in the absence of Behe's incredulity. And one more question for DNAUnion, and I would really like an answer in order to make this debate move along. Why does Behe exclude macroscopic/skeletal IC systems? It would seem that if such systems came about in the fossil record in "one fell swoop", his theory would only be strengthened. It would be like evolutionists discounting genetic data that shows no common ancestor but relying on morphology alone to show common ancestry. You can't pick and choose once you make predictions.
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Peter Member (Idle past 1507 days) Posts: 2161 From: Cambridgeshire, UK. Joined: |
As I said, which one of the ossicles can you remove
without 'breaking' the vibration transmission system?
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MrHambre Member (Idle past 1421 days) Posts: 1495 From: Framingham, MA, USA Joined: |
quote:Good question. After hitching the intelligent-design-creationism wagon to 'irreducible complexity' and defining it for all to see, he then denies that it applies to organs. I've already stated that the human heart sure seems 'IC': if you take away the pump or valves, you don't, well, catch mice, in Behe's words. However, there seem to be problems defining anything as 'IC,' even Behe's pet subject the BacFlag. Ian Musgrave, of the University of Adelaide, argues in his hypothetical scenario for the evolution of the bacterial flagellum that certain parts of the BacFlag can be removed and the system still seems to function. So the concept of 'IC', then, isn't the crux of the debate. The biological structures themselves may or may not be 'IC' depending on how we define them (don't get me started on Dembski's notion of the BacFlag as a discrete combinatorial artifact) or their function. The argument itself concerns developmental pathways, and Behe realizes that it's much easier to make a convincing case for the evolution of the complex human heart than for the BacFlag. Behe, obviously, is not the first one to assert that property A is proof of design. It doesn't matter what the proposed litmus test is, what matters is that we're never told why property A is proof that natural law is not inviolable and that divine intervention has taken place in Nature. I don't consider 'irreducible complexity' any better than any other candidate for property A. We have no clear understanding of why natural processes could not conceivably account for an 'IC' system in biology, and certainly no evidence that intelligent agency accounts for the origin of any biological structure. regards,Esteban "Cilia Thing" Hambre
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DNAunion Inactive Member |
quote: You're mixing apples and oranges. When specifically discussing Behe's statements on IC then if a "part" is deleted and the result is just reduction in fitness, not loss of minimal function, then the "part" is not considered to be one of the required parts of the IC system itself.
quote: Agreed (more or less...your statement makes it sound like it is clearly wrong that I couldn't find any references in my textbooks, which is not the case). I learned something, and already thanked you. [This message has been edited by DNAunion, 03-10-2004]
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DNAunion Inactive Member |
quote: Sure...from my personal notes (people can skip the introduction and head straight for the quotes, if they want, without losing anything). ***************** How many people here truly understand how a computer operates? Probably not many. I would imagine that most users know little more than what button to push to turn the computer on and what a monitor, keyboard, and mouse are (for example, many people point to the system case sitting on their desk or floor and call it a CPU!). Ask them how a CPU fetches instructions and a convincing answer will not be forthcoming. Others know computers in a bit more depth. They know that there is a thing called a hard drive that somehow holds all of their information, and that some kind of a green circuit board inside the system case houses something called the CPU (which they have no idea what it looks like) that does the thinking, etc. Understanding computers a bit better than the first group, those belonging to the second group could give a better explanation of how a computer operates. A few others know a great deal about computers. They know of the binary language and its physical representation as the presence or absence of electric charge; that a hard drive contains multiple rigid platters that spin at high rates and have read-write heads (or separate read heads and write heads) that float on a thin cushion of air just above the platters’ surfaces; and that the BIOS serves as an abstraction layer between the given hardware configuration and the operating system; etc. These people could give a very detailed and convincing explanation of how a computer operates. What we see here is that - as with most everything that science studies - the whole is understood better by learning how its parts operate. And if the parts are themselves composed of smaller parts, an even greater depth of understanding of the whole can be reached by determining how they function too. This process of drilling down to deeper and deeper levels produces a fuller, more-thorough picture of the whole. This is reductionism. Life. That is what we are interested in. There are different organizational levels of life. Obviously, there is the level of the organism. For centuries, the only organisms known were plants and animals, and the organismal level was as far as biology had delved. Let’s stick with animals, since much of our knowledge of life was originally derived from them. How does an animal work? No one knew for sure. Animals jumped, ate, mated, slept, and died but detailed explanations of how these actions occurred were not known. As time went by, biology dug deeper and found that animals are composed of organ systems, which are themselves composed of organs. Then more detailed explanations could be provided (for example, the path that food took through the body and the fact that blood circulated instead of irrigating the body and then new blood being produced to replace that which was pumped out of the heart). But even this level did not suffice. Further research dug deeper into the tissue and cellular levels of organization. More detailed explanations were available. Indeed, each deeper level that was examined led to a greater understanding of how life operates. And within the last 100 or so years, the innards of the cell have been being investigated, leading to an even more complete understanding of life. So to understand most fully how life works, and in order to provide the most detailed and convincing explanations for life-related phenomena, we have to dig down to the deepest levels of biological systems: biochemistry (gross anatomy is at far too high of a level).
quote: quote: quote: quote: quote:
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DNAunion Inactive Member |
quote: Besides the quotes I gave above, Behe also says this about the panda’s thumb:
quote:
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