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DNAunion: I already pointed out that there is more to IC than a one-sentence definition.
Same goes for other things dealing with science, such as evolution. One of the most-used definitions of evolution is "changes in allelic frequencies in a population". If we stick to just that definition then we can't legitimately state that dinosaurs or trilobites evolved because we don't have access to their alleles.
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NosyNed: I'd be tempted to argue that we do have access to the alleles since they show up in the phenotypes.
But then you’d be bringing in a new concept; one that is not part of the one-sentence definition of evolution. How is that materially different from bringing in the concept of minimal function into Behe’s usage of IC, which he mentions several times in his book?
Also, it is
possible for a phenotype to change without there being an associated change in allelic frequencies. This can happen if the number of each allele in the population remains constant but their distribution — between heterozygotes and homozygotes — changes.
PS: I am not arguing against evolution, just making a point about the inadequacy of many one-sentence definitions.
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NosyNed: However, I agree that things can be oversimplified. But I don't see more in Behe's definition of IC (other than restricting it to biochemical systems). Is there more to it?
Yes. Here is something I wrote up several years ago, back when I was an IDist (if one must pigeonhole). Even it is not complete (minimal function is not mentioned, nor are other things).
PS: I should point out that I am posting this as is, without updating it.
3) IRREDUCIBLE COMPLEXITY
Irreducible complexity is best defined by Dr. Michael Behe, who coined the term in his 1996 book Darwin’s Black Box: The Biochemical Challenge to Evolution. On page 39 of that book, he states:
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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.
So any system that has all 6 of the following attributes is IC:
(1) SINGLE SYSTEMThe system must be a single system. It cannot be a composite system, such as an automobile. Even though the reciprocating, four-stroke, internal-combustion engine of a car is probably IC, the car itself is not because its sound system and its air conditioning system can be removed without the car losing its function. These systems that could be removed without the car losing function are subsystems of the car (which means that a car is not a single system, but is rather an aggregate system composed of multiple systems). Not even the eye — which many people would simply assume counts as a single system — meets this criterion, as Behe points out.
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Both Hitching and Dawkins have misdirected their focus. The eye, or indeed almost any large biological structure, consists of a number of discrete systems. The function of the retina alone is the perception of light. The function of the lens is to gather light and focus it. Tear ducts and eyelids are also complex systems, but separable from the function of the retina.
Hitching’s argument is vulnerable because he mistakes an integrated system of systems for a single system, and Dawkins rightly points out the separability of the components. (Michael Behe, Darwin’s Black Box: The Biochemical Challenge to Evolution, Free Press, 1996, p38)
(2) SEVERAL PARTSThe single system mentioned in (1) must be composed of
several (i.e., at the absolute minimum, three) parts. A two-part system that requires each part - such as a natural lever system formed by one pine tree falling perpendicular to and on top of an already fallen pine tree - is not an IC system (note that such a fallen-tree-lever system also fails the criterion of parts having to be well matched, which will be discussed next). Everything else being equal, the greater the number of (interacting) parts in a system, the greater the system’s complexity; and the underlying concept of Behe’s book and argument is irreducible
complexity, not irreducible
simplicity.
(3) WELL-MATCHED PARTSThe several parts mentioned in (2) must be well matched. That is, the parts should physically fit together (and work together) so well that a change in one part’s size and/or shape would require compensatory changes in at least one other part’s size and/or shape. In addition, a well-matched part must be a solid, not a fluid.
For example, for a standard mouse trap (the object Behe uses to explain his concept of irreducible complexity), decreasing the length of the holding bar by half would necessitate an equivalent reduction in the size of the hammer as well as a large-scale adjustment in the position of the catch and probably the spring also. Similarly, doubling the length of the hammer would also necessitate concomitant changes in other parts: the holding bar’s length would need to be doubled, and its girth may need to be increased in order to handle the additional load, the catch would need to be repositioned, the length of the base would need to be increased, and a repositioning of the spring may be required. For an IC system, the parts’ sizes and shapes should be somehow specific to each other: generic parts are not well matched to each other.
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The appearance of the modifier "well-matched" in the definition I constructed reflects the fact that complexity is a quantitative property. A system can be more or less complex, so the likelihood of coming up with any particular interactive system by chance can be more or less probable. As an illustration, contrast the greater complexity of a mechanical mousetrap with the much lesser complexity of a lever and fulcrum. Together a lever and fulcrum form an interactive system which can be used to move weights. Nonetheless, the parts of the system can have a wide variety of shapes and sizes and still function. Because the system is not well-matched, it could easily be formed by chance.
Systems requiring several parts to function that need not be well-matched, we can call "simple interactive" systems (designated 'SI'). Ones that require well-matched components are irreducibly complex ('IC').
let me first illustrate a well-matched system using the blood-clotting cascade (Stubbs and Bode 1994). The active form of one protein of the cascade is called thrombin, which cleaves the soluble protein fibrinogen to produce fibrin, the insoluble meshwork of a blood clot. The chemistry catalyzed by thrombin is simply the hydrolysis of a certain fibrinogen peptide bond. However, all proteins are made of amino acid residues joined by peptide bonds. A typical protein contains several hundred peptide bonds. There is nothing remarkable about the bond in fibrinogen that is cleaved by thrombin. Yet thrombin selects that particular bond for cleavage out of literally hundreds of thousands of peptide bonds in its environment and ignores almost all others. It can do this because the shape of thrombin is well-matched to the shape of fibrinogen around the bond it cleaves. It "recognizes" not only the bond it cuts, but also a number of other features of its target. The other proteins of the clotting cascade (Stuart factor, proaccelerin, tissue factor, and so on) have similar powers of discrimination. So do virtually all of the components of the molecular machines I discussed in Darwin's Black Box. (http://www.discovery.org/viewDB/index.php3?program=CRSC%2... )
So what does well-matched mean? I’ll give it a shot.
3a. Strong sense
match = to fit together (related to proper size and shape)
well = (1) to a high degree, and/or (2) to a large extent or degree, and/or (3) to an extent approaching completeness, and/or (4) without doubt or question
Well-matched: Physically fitting together both precisely and specifically due to having exactly the correct sizes and shapes (tailor made). A change in the size and/or shape of (at least the interacting portion of) one part would necessitate a compensatory modification to the size and/or shape of (at least the interacting portion of) the other part.
Example: An enzyme possessing great specificity for its substrate (due to their complementary, three-dimensional, recognition surfaces), or the moving, interlocking gears of either a transmission or a mechanical clock (they mesh together perfectly).
3b.Weaker sense
match = to fit together (related to proper size and shape)
well = (1) in a good or proper manner, or (2) satisfactorily with respect to conduct or action
Well-matched: Physically fitting together properly - that is, satisfactorily enough to perform a particular action — due to having appropriate sizes and shapes. Though the two parts may not interlock or have large areas of complementary surface contact as they do in the strong sense, the size and shape of (at least some region of) each part are still constrained to being within certain fairly narrow parameters. If the size and/or shape of one part were changed by more than a trivial amount, a compensatory change in the size and/or shape of the other part would be required.
Example: The holding bar on a mechanical mouse trap that restrains the hammer from moving.
So what does well-matched not mean?
Argument: If a system is able to function, then its parts must be well matched.
Counter: A functioning lever system made of non-well-matched parts can be produced by numerous different-sized and/or different-shaped objects (diving board, refrigerator, bookshelf, tree branch, car, etc.) coming to lie perpendicularly across a fallen pine tree.
Argument: If a system is able to function well, then its parts must be well matched
Counter: A functioning lever system consisting of non-well-matched parts (such as was just described) can perform its function well.
Argument: In a water-channel system, water is a well-matched part as it perfectly fits the specific three-dimensional contours of the other parts (the two sides and bottom)
Counter: Fluids do not fit Behe's usage of "well-matched". His usage of "well-matched" pertains to
solid objects that physically fit together well due to their shapes and sizes. If a fluid (liquid or gas) is poured into a cylindrical container, it will immediately conform to that particular shape (becoming cylindrical). If that very same fluid were then poured into a cubic container, it would immediately conform to that particular shape (becoming cubic). If that very same fluid were next poured into a container of irregular shape, it would immediately conform that that particular shape (becoming irregular). And if a liquid were poured out onto the floor, it would immediately conform to the floor's particular contour (becoming flat). A single fluid (liquid or gas) conforms to whatever shape it is contained in. As such, it cannot be considered a well-matched part according to Behe's usage. The reason? Lack of specificity: fluids are the ultimate conformers. In the following quote, Behe explains that the components of the BZ reaction are not well matched because those parts are generic and fit a wide range of other parts that are not components of the system under consideration.
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BEHE: Let's contrast this biochemical specificity [of the specificity of the blood-clotting enzymes] with a comparable chemical reaction lacking such specificity. The peptide bonds of proteins can also be cleaved by simple chemicals. A typical procedure calls for incubating the protein in 6N hydrochloric acid at 110C for twenty four hours. If fibrinogen were incubated under those conditions, the peptide bond that thrombin leaves would be broken, but so would every other peptide bond in the protein. It would be completely reduced to amino acids. If thrombin were in the mix, it too would be completely destroyed. If the other proteins of the clotting cascade were there, no clotting would take place, even though the peptide bonds that are cleaved in the cascade would be cleaved, because all other peptide bonds would be hydrolyzed too. There is virtually no specificity to the chemical hydrolysis beyond the type of bond that is cleaved.
Similarly, the reactants of the BZ reaction are small organic or inorganic chemicals that show little specificity for each other. One ingredient, sodium bromate, is a general purpose oxidizing reagent and is capable of degrading a very large spectrum of chemicals besides the ones used in BZ reactions (thus its transport aboard airlines is forbidden). Another requirement of the reaction is simply for a transition metal that can change its oxidation state, and a number of such metals are known, including iron, cerium, and manganese ions (Field 1972). A third requirement is for an organic molecule that can be oxidized. Many candidates could fulfill this role (ones that have been used include malonic, citric, maleic, and malic acids), and organic molecules can be oxidized by many reagents other than bromate. The last ingredient is simply a high concentration of sulfuric acid. As Field (1972, 308) noted, setting up BZ reactions "is an exceedingly easy task as they will occur over a wide range of concentrations and conditions."
(http://www.discovery.org/viewDB/index.php3?program=CRSC%2...)
(4) INTERACTING PARTSThe several parts mentioned in (2) must interact. A system that is composed of non-interacting parts is not IC. This includes:
4a. A system in which the components are stationary/static. For example, the pieces of a standard jigsaw puzzle inter
lock, but they do not inter
act.
4b. A system in which the components are arranged in a simple serial manner, with each one acting upon the next in line (such as a line of falling dominoes). Here the distinction is between acting and
interacting.
The problem with 4b is that the parts are merely acting on the next in line, as opposed to interacting with multiple other parts in various ways. It is clear that there is a distinction between:
4b-1: A system composed of a series of things in which each is merely
acted upon by (and/or dependent upon) the next in line (such as a food chain, or an A->B->C->D metabolic pathway).
4b-2: A system composed of a group of things arranged into an
interacting (and/or interdependent) network, with each of the parts acting/depending upon multiple others such that various linkages run from each part in multiple directions to form a complex meshwork of
interacting (and/or interdependent) parts (such as a food web, or a mouse trap).
Interactions that are made by forces being applied through direct, physical contact are clearly interactions; in the strong sense of the word. Interactions that occur only logically, or indirectly through intermediaries, are not clearly interactions of the type Behe requires (they are interactions in the weak sense and would need to be examined individually).
(5) PARTS CONTRIBUTE TO OVERALL FUNCTIONEach of the several parts mentioned in (2) must contribute to the system’s overall function. An accessory part is a part of the general system that (1) is not required for the functioning of the core IC system or (2) performs a function that does not tie directly in with that of the core IC system. For example, a mechanical mouse trap could have a rubber pad added to its base in order to make the trap easier to grasp or to dampen the sound of the SLAP associated with the forceful impact of the hammer with the base. But the rubber pad would not contribute to the catching of mice and so would serve a function unrelated to the overall function of the device. Any such accessory part does not count as being a part of an IC core system and must be eliminated from the parts mentioned in (2).
(6) ALL PARTS REQUIREDRemoval of any one of the several parts mentioned in (2) causes the system to lose function. A system can have an IC core with accessory parts added on. Consider again a rubber pad added to the base of a mechanical mouse trap. We already saw that the pad is an accessory part because it serves a function unrelated to the overall system’s function. But even if that weren’t true, the rubber pad would still be a mere accessory part because it could be removed without leading to the loss of system function. In such a case, the accessory parts are part of the overall system, but they are not part of the *IC* core system, and must be eliminated from the parts mentioned in (2).
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The reason for the conclusion [that a watch must be designed] is just as Paley implied: the ordering of separate components to accomplish a function beyond that of the individual components. The function of the watch is to act as a timekeeping device. Its components are the various gears, springs, chains, and the like that Paley lists.
So far, so good. But if Paley knows what to look for in his mechanical paradigm, why did he go downhill so quickly? Because he got carried away and started looking to the wrong features of the watch. The problems start when Paley digresses from systems of necessarily interacting components to talk about arrangements that simply fit his idea of the way things ought to be. The first hint of trouble comes in Paley’s opening paragraph, when he mentions that the watch’s wheels are made of brass to prevent rust. The problem is that the exact material, brass, is not required for the watch to function. It might help, but a watch can function with wheels made of almost any hard material — probably even wood or bone. Things only get worse when Paley mentions the glass cover of the watch. Not only is the exact material not required, but the whole component is dispensable: a cover is not necessary for the function of the watch. A watch cover is simply a convenience that has been attached to an irreducibly complex system, not a part of the system itself. (bold emphasis added, italic emphasis in the original, Michae lBehe, Darwin’s Black Box: The Biochemical Challenge to Evolution, Free Press, 1996, p 215-216)
Note that confusion often arises when people remove what they believe to be a part from a system Behe determined to be IC with the resulting system still being functional (which appears to refute Behe’s claims). The problem is usually that these people are not removing a part of the IC system, but rather are removing either an accessory part (see (5) and (6) just above) or a part of one of the parts of the IC system. For example, consider a system that typically has say 12 copies of a rod-like structure that together form some sort of a barrel that is one of the several parts of the IC system. Someone may find that 1, 2, or 3 copies of the rod-like structure that combine to form the barrel can be removed without the system losing function. They might then claim to have falsified an example of IC, but they would be wrong. The barrel — which was the part of the IC system - is still there, functioning as it was before: it itself just has fewer components now than before. So this would not be the removal of a part of the system, but rather the removal of a part of a part of the system (it would be merely a subpart of the system that was eliminated). The individual parts of an IC system do not have to be IC themselves: parts of a part of the IC system, or copies of a multi-component part, can be taken away from an IC system without the resulting system losing function, without contradicting Behe’s definition/example at all.
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