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|Topic: Irreducible Complexity (Slevesque & Dr Adequate Only)
Member (Idle past 4612 days)
Behe defined an irreducibly complex biological system as a system which is "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".
Creationists, following Behe's lead, often claim that irreducibly complex structures cannot evolve (to be more precise, cannot evolve by the processes detailed in the theory of evolution).
The argument is that an irreducibly complex system of n parts can't have evolved because natural selection would not have favored the evolution of the first n-1 parts of the system, because the first n-1 parts of the system would have conferred no selective advantage to the organism until the nth part was added to the system.
(I believe that I have stated the creationist position fairly: it is no desire of mine to argue against a straw man, and if any creationist would like to refine this argument by quoting from Behe, I should welcome the intervention.)
I made the argument from parts being steps, and in biological systems, the basic unit for steps are mutations.
And yet we can see in the fossil record how this evolved. (Or, if you are a die-hard creationist, at least admit that we can see in the fossil record how this could have evolved.) We have the intermediate forms (or, if you are a creationists, the things that look exactly like intermediate forms) showing how the incus and malleus took on their present form and position and role by gradual adaptations of form and position and function from the quadrate and articular bones of the reptilian jaw.
Just to be clear, if you're a creationist, you don't have to concede that this is how the mammalian middle ear evolved. It is, but let's save that argument for a rainy day.
No, my point is that the evolutionary explanation for the middle ear involves gradual shifts of form and position and function. Behe's argument fails because we don't need to imagine an evolutionary process in which (for example) the malleus and the stapes came first, and then the incus poofed into existence to fill the gap between them.
The sequence in the fossil record shows that we don't have to envisage a scenario where two of the three parts acquired their modern form and position first and then the third was tacked on. And even if you are a die-hard creationist and don't think that the fossil record is evidence of anything, nonetheless you must concede that we can see how the irreducibly complex system might have been produced by ordinary evolutionary modifications, and without two of the parts evolving and then the third being added.
Now, the first point of contention is if I find any convincing evidence that the reptilian ear did in fact become the mammalian ear, through a series of steps that natural selection would favor.
And this one of the problems your going to have if basing yourself on big anatomical features and transitions from the fossil record. You have to show a series of mutations that lead from one to the other, and you'll find it almost impossible to do using gross anatomical features such as bones, and even more using fossils instead of living animals, because at best you show 8 intermediates, in a transition that probably involves hundreds of mutations.
There is a distinct reason why IC systems in biology are analysed only at the biochemical level with the pieces being proteins and such, it is because the analysis of an advantageous mutational pathway to a IC system will be much, much, much more easier to discern.
But putting this aside, and supposing that I do accept that I see how this could have evolved, then I still see a blatant problem with this example, the three bones are already contributing to the hearing system of the reptiles:
In fact, even in modern reptiles the quadrate and articular serve to transmit sound to the stapes and the inner ear (see Figure 1.4.2).29+ Evidences for Macroevolution: Part 1
And this strongly suggests to me, that this is an example of an already irreducibly complex system of three parts, where you modify the arrangements of the three parts and end up with a different version the same IC system that still does the same thing.
Let's take another example. Mammals have two jaws to grasp and chew their food with: an upper and a lower jaw. Remove one of these parts, and all function is lost --- one jaw is about as much use for chewing as one millstone is for grinding. This structure is therefore irreducibly complex.
So, what can we conclude? Clearly, this: that the evolution of this system can't have occurred by one jaw developing first and then the second one being added to make the complete system.
And guess what? No biologist anywhere ever has claimed that this happened. Instead, they trace the evolution of jaws from pharyngeal arches ("gill arches") which already had a lower and upper half before they functioned as jaws. Fossils of interest include the early chordates Yunnanozoon and Haikouella, which have no jaws but which possess pharyngeal teeth.
(Some modern fish also have pharyngeal teeth on the pharyngeal arches behind their jaws. Here's a picture of pharyngeal teeth in modern carp.
In cichlids, the lower left and right first pharyngeal arches have fused together to form a lower "pharyngeal jaw" behind the true jaw.)
Now, whether or not you accept the evolutionary explanation for this irreducibly complex structure, it's plain that the fact that it is irreducibly complex does nothing to argue against the evolutionary explanation, since the explanation does not involve the system evolving one jaw at a time, nor yet two fully-formed jaws simultaneously appearing at a single stroke, but rather the gradual processes of adaptation of form and function that one associates with the theory of evolution --- that is, with the actual theory of evolution, the one in biology textbooks, rather than the imaginary theory of evolution that must have been rattling around in Behe's head when he came up with this stuff about irreducible complexity.
Your explanation of all this is very difficult to understand, hopefully I understood it correctly.
In this case (once again, if I accept that I can see a possible pathway between fish gill arches and mammalian jaws) is that you start of once again with an upper and lower pieces already in the right place, and end up with these same pieces at the same places but this time changing function, and now serving as a jaw.
Another problem is, of course, that the jaw isn't a two piece system. It has many other pieces such as tendons, nervous circuits, etc. etc.
I would suggest, for the reasons mentioned earlier, that you stick to biochemical systems, and also because all the pieces of such systems and associated mutations are more easily identifyable. And of course, this will keep us on the terrain of experimental, presently observable processes and science, which is going to be easier for both of us to come to the same conclusions about those systems (contrary to fossils, which you can't expect of me to continually accept that there is a pathway between fossils just for the sake of the topic at hand)
As a final example, divide yourself (conceptually) into two parts --- your head and everything else. A series of experiments conducted by the French researcher Dr Joseph-Ignace Guillotin have proved conclusively that one is useless without the other. You yourself are an irreducibly complex system.
And this would be a strong objection to any evolutionary scenario involving a bunch of human heads rolling about without bodies for a few millenia; or, alternatively, a bunch of headless people strolling around and bumping into things.
But this is not the scenario that biologists have put forward. Instead, they suggest that the process involved gradual encephalization starting with a segmented ancestor whose frontmost segments played no special role.
Again, you can believe that or not; but it is no objection to this theory to point out that today the human head+body that represents one of the end points of that process forms an irreducibly complex system. It is only an objection to a hypothesis in which heads magically appeared on human bodies which previously had lacked them, or vice versa --- a hypothesis to which no-one at all subscribes.
This example tends to show that you aren't really interested in a genuine discussion, which was to expected I guess.
But say I take the example seriously. The basic irreducibly complex part of this is the IC aspect of multicellularity. It is a basic aspect of it that cells are interdependent and cannot survive without the others.
This in fact is a prime test for IC: if IC systems can evolve naturally, in no other area should we be able to better observe this then in the evolution of mulicellularity from unicellularity. The environment around us is filled with billions of unicellur organisms, of generation times in the span of minutes sometimes. If multicellularity was evolvable, then we should routinely observe every step of the process around us at any given time. We do not, and we do not observe it either in the fossil record, where multicellular organism appear all at once with no trace of the intermediates. Clearly, the only reasonable conclusion is that no paths exist for multicellularity, appart from mind-boggling randomness and luck, maybe.
Take your time to answer, as I have obviously taken more time then I planned.
AbE I know I am making some grand contentious claims here regarding multicellularity, but this was wanted to get the discussion in that direction, so you can drop any snarky comments you could plan up
Member (Idle past 4612 days)
Well no. As I said repeatedly about my examples, it makes no difference to the goodness of my argument or the badness of Behe's whether you believe this actually happened or not.
The point is simply that an evolutionary explanation need not involve the last step and final mutation being one that poofed the incus (for example) into existence fully-formed to fit between the malleus and the stapes.
Once we have taken note of this, we can see why Behe's argument fails.
The thing is, that thinking that it did happen is the only way of thinking that it could happen, in this particular case of using fossil evidence (I'm highlighting this so you don't take the previous out of context), because you haven't actually demonstrated a step by step pathway in which each step is favoured by natural selection.
No, for the same reason. I don't have to show this at all. I have to argue that the last mutation was not necessarily one which poofed a fully formed part into place into a structure which was identical to the existing structure apart from missing that part.
But no one is claiming this, and wanting to represent Behe as if this is what he's claiming is clearly fallacious.
The thing is, the mechanism you are proposing to explain IC systems is not some sort of continuous morphing, but a step by step process fo mutations and Selection.
Yes, but they're not necessary to do so --- as you can see from the diagram of the reptilian ear in the website you reference, the stapes alone will transmit vibrations from outside to inside the ear. And this is not true of the mammalian ear.
Two unsupported assertions, unfortunately.
Oh, you're doing this to make things easy for us?
You can stop doing us favors now.
It is to make it easy for us, meaning the both of us.
Keep in mind, I have no personnal investment in the idea of IC, my worldview functions perfectly well without it, and it's not my idea. If it were to be shown to be unreliable I would gladly conclude so. Note that in the two years I have been here, this is the first time I discuss this subject, and this was only because someone foolishly (in my opinion) claimed that it had been ''utterly and completely demolished'', showing that I myself am hesitant to put much weight to it, and that my intention is to show that, at the very least, credit is to be given were credit is due, and that Behe does not deserve to be treated like a complete idiot.
I think it makes sense to analyze the jawbones as a system. Can you come up with some sensible criterion for a biological system such that this doesn't make sense?
Well, first I don't see how the two jawbones could perform functions on their own, functions such as, you know, chewing.
(After all, the bacterial flagellum wouldn't do anything useful unless it was attached to the rest of the bacterium, and yet I don't hear any creationist complaining that that doesn't qualify as an example.)
In counter-part, that is because all the relevant pieces for the flagellum to perform it's function are being considered into the system. You can't say the same about your two-piece jaw system
In the first place, this is a non sequitur; in the second place the conclusion is not merely fallacious but false; in the third place we can observe multicellularity evolving; and in the fourth place I don't see what this has to do with IC.
This is directly related to IC, because the IC nature of multicellular systems is what makes the crude example of ''head and body'' an IC system.
Where an intermediate would be what? An organism consisting of one-and-a-half cells?
(As a matter of fact, in our observations of the evolution of multicellularity the first step is not even from one cell to two. But again we seem to be straying from the topic.)
The advent of life, and coordinated multicellularity are two points where we can agree (I hope) that it is clear that they are the advent of IC systems.
Multicellularity arises when the selection is made at the level of the organism, not at the level of the individual cells, and reproduces as a single organism.
These two areas, the origin of life, and the origin of multicellularity are of particular interest because we should be able to observe every single step all around us. It should like being in a forest, where you don't need to see a tree's entire life to know each steps it goes through because of the vast amount of trees around you, where each tree is at a different stage. (Same analogy with stellar evolution)
Member (Idle past 4612 days)
You do know that argument by analogy is fallacious reasoning, even though it is helpful to sometimes illustrate a discussion.
In this case, the analogy clearly does not apply. You are making the claim that there exists a pathway of single mutations, where as each step is favored by natural selection to go from one to the other.
In other words, you are making a claim about the mechanism it happened by. Not the historicity of the event. Behe, being a theistic evolutionists, would agree with you that mammals descended from reptiles and the fossil evidence for this, but he would disagree on the mechanism.
Member (Idle past 4612 days)
Sorry end of semester studying is underway, but I haven't forgotten this.
In fact I have been reading 'Irreducible complexity revisited' (http://www.designinference.com/....Irred_Compl_Revisited.pdf) in my spare time and I have just finished reading it.
I'll be posting a reply hopefully tomorrow. I guess you can read Dembski's paper if you have the time, it would help the discussion
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