Do you see IC as the savior of the Intelligent Design “theory”? Well, then, I would suggest that you don’t go and read this.
Irreducible complexity, intelligent design’s closest brush with biology, is marked by three ironies.
IC is supposed to be important because it cannot evolve. But it can evolve, in the same ways that anything else does.
Not one of the impressively complex biochemical systems said to be IC by IC/ID proponents has been shown to be in fact IC and several are known not to be. The known cases of IC are simpler and their evolution is understood.
Although the subject is religiously motivated, proponents have focused on bacterial flagella as the last hope for a highly complex IC system. This has the unintended consequence of making The Designer (aka God) responsible for serious diseases.
It is easy to see why scientists are not impressed by the claim that IC cannot evolve. IC is a matter of an observer specifying a combination of function, parts and system so that the specified function requires all the parts. There is no way for evolution to be sensitive to this, no way for it to matter at all. Nor does nature care about ‘direct’ vs ‘indirect’ evolution as perceived by us. Indirect evolution is as normal as tails on cows. Evolution merely requires populations with heritable variation. The processes of mutation, natural selection and random drift are not sensitive to whether a change will be deemed direct or not, nor whether a function, system and parts as specified by some observer are changing to meet the ‘all parts required’ condition.
There was supposed to be a special reason why it was impossible or at least very difficult for evolution to arrive at an ‘all parts required’ situation, but there is no such reason. The proposed reason was based on overlooking standard evolutionary processes and making analogies to manufactured items. Comparing Behe’s mousetrap to Venus’ flytrap confirms the reasonable suspicion that analogies and arguments based on manufactured items lead to underestimating nature. Since IC can occur in the ordinary course of events we have a known process, evolution, which is acting in the present and which given time is sufficient to produce the adaptations that Behe finds perplexing. This is like the raising of the Rocky Mountains; a known process acting in the present is sufficient, given time, to produce the result. Of course there is no way to predict all the details in either case, nor is it necessary.
Some people who believe in ID use the irreducible complexity argument like some kind of mantra - “we don’t understand how these complex systems could have developed, therefore they could not have developed, therefore evolution is falsified”.
If you don’t want to read all of the article linked to above, then how about this:
This (irreducible complexity - ed) is the classic argument from design; however, it is based on an incomplete understanding of the mechanisms of evolution. Evolution is not random; adaptations are not produced by “chance.” Mutation does produce random (chance) variation, and if mutation were the only mechanism of evolutionary change, it would be a random process. However, natural selection, a nonrandom process, acts on this random variation to produce adaptations like the eye.
Likewise, irreducible complexity arguments state that complex organs are “irreducibly complex,” you cannot take away one of the “parts” and still have a functional organ, therefore, it must have been made all at once. Evolution by natural selection does not make a complex organ all at once. They are the products of many small changes (produced by mutation) that are selected for, modified, and that accumulate over a long period of time. Each of the intermediate steps is functional. For example, there are many gradations in light-sensing organs, from the very simple to the very complex (vertebrate and molluscan eyes), and each of these serves an adaptive function for the organism. See Kenneth Miller’s book: Finding Darwin’s God for an excellent analysis of design and irreducible complexity arguments.
You may also hear probability arguments, in which an astronomically small probability is stated that some trait evolved by natural causes. Again, these arguments are based on the assumption that the trait appeared in its current modern form all at once. Indeed, this would be highly improbable. However, this is not the way evolution works. Evolution by natural selection is a gradual, step-by-step process, with incremental changes occurring through mutations that are then selected for if advantageous.