Irreducible complexity is a concept popularized by Michael Behe in his 1996 book Darwin's Black Box to support intelligent design. Intelligent design pushers argue that while some systems and organs can be explained by evolution, those that are irreducibly complex cannot, and therefore an intelligent designer must be responsible.
Irreducible complexity stems from the claim that some biological systems appear to be too complex to have arisen by natural selection. Specifically, it argues that if you take a part away from an organism and it stops functioning (analogous to taking the engine out of a car) then it must be irreducibly complex and cannot have evolved. It is one of the main arguments of the Intelligent Design movement.
The concept is considered to be mostly bollocks when applied to evolution because it fails to take into account numerous other pathways that a particular ability can evolve through - it assumes that evolution must go through "additive" processes to achieve its conclusion and this isn't the case. Most evolutionary biologists do not consider it science by any stretch of the imagination because the idea relies on personal incredulity and specific examples are non-falsifiable.
There is a slightly different definition of "irreducible complexity" related to emergent phenomena in systems theory and computational complexity theory. However, a full explanation of this is beyond the scope of this article. It is believed that Michael Behe has basically taken some of the ideas found within this theory and rehashed it slightly to apply to evolution. Behe's definition is that an irreducibly complex form 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"
While surrounded by some fancy words and the language of science, this is just incredulity that the world could arise through naturalistic processes. The argument is no more advanced or "evolved" than William Paley's "Watch Argument" which stated that as a watch looked created, it must have a creator. Essentially, Behe is stating "because I can't see a natural explanation, Goddidit" - this ignores any possibility that a naturalistic explanation or evolutionary pathway will later be discovered.
 Probability Analysis
In calculating the probability for a mutation, one must consider not merely the probability that the mutation will arise, but the number of opportunities for that mutation. So if a mutation has only a one-in-a-million chance of happening, it's still very likely that the mutation will eventually occur if the species has millions of members. So now the question arises: if there are several different mutations under consideration, do we multiply all the probabilities together, and then compare the probability to the number of opportunities, or do we compare each probability to the number of opportunities, and then multiply the adjusted probabilities together? Evolutionary theory suggests that we should generally do the latter; each mutation can arise independently, spread through the population by natural selection, and combine through sexual reproduction (or gene transfer in simpler organisms). Proponents of irreducible complexity assert that in some cases, the individual mutations do not provide any advantage by themselves, and so are not operated on by natural selection, and we must multiply the probability of all of the mutations first before considering the number of opportunities.
“”"I think I have now finally understood what "irreducibly complex" really means: a statement, fact or event so simple it cannot be simplified any further, but still too complex to be grasped by a creationist."
 Explanation from uncyclopedia
An argument that states that because something doesn't work when broken down to its component parts it must be impossible for it to have been developed gradually.
Or something that Michael Behe, after sitting down and thinking for, sometimes, as long as 5 minutes, cannot explain without recourse to an intelligent designer.
 Examples of flawed arguments
Frequently, believers in this philosophy cite the eye as an example of something too complex to have evolved. The argument is frequently presented with a question of the type, "What use is half an eye?". However if the question is recast as "Given a choice, would you prefer to be completely blind or have 50% of your present vision?", then it becomes clear that the question is badly formed, especially when keeping in mind that many species manage to survive with significantly less advanced eyes. Examples include the polychaete worms, which can distinguish between light and dark; the simple eye-cup of the flatworms, for finding the direction of a light source; jellyfish and scallops, with simple eyes for detecting movement; the famous compound eyes of the insects, which can make out simple shapes, and ultimately the sophisticated single-lens eyes of the molluscs and vertebrates.
Another famed and also flawed example is "the watch on the beach." It goes as follows: "if you find a watch on the beach, do you assume it got there by chance, or do you assume it was made by an intelligent designer?" The example is flawed because watches and their parts do not reproduce or mutate. (And if they did, they could be produced by random mutation.)
The above arguments are appeals to the common sense of the "Average Joe." Popular support is, however, not part of the scientific method; this can be easily understood when considering that a significant part of the world's population believes in astrology.
Although irreducible complexity is offered as evidence of intelligent design, this conclusion is questionable. Robustness is generally considered to indicate good design, not precariousness. Which parachute would you consider better designed - one which ceased to function if a single part was missing, or one which has a back-up pullcord? Irreducible complexity is at best evidence for crappy design.
Behe also has defined and redefined irreducible complexity:
“”In response to these demonstrations however, IDC proponents belatedly ‘reinterpret’ their initial claims in order to lift them out of the critic’s reach. A first strategy to this end consists in shifting the burden of proof from plausible evolutionary pathways to the actual evolutionary story, maintaining that the broad outlines of a plausible evolutionary account amounts to nothing more than Darwinian wishful thinking and speculation. The same bait-and-switch technique can be discerned here: IC is constantly boasted as a point of principle for ruling out the possibility of evolutionary explanations, but as soon as it is challenged on that ground, through a discussion of plausible evolutionary scenarios, ID creationists pretend that they were talking about actual evolutionary pathways all along.
When they are confronted with tangible evidence of actual evolutionary history, IDC theorists resort to a second strategy, shifting their design claims to the remaining parts of the evolutionary puzzle, as if the ‘real’ problem was always there. For example, Kenneth Miller (2004) beautifully demonstrated the structural similarities between one component of the flagellum and the so called type III-secretory system. He convincingly argued that the former is a very plausible evolutionary precursor of the latter, which has been co-opted by evolution to perform a new function. In response to this embarrassing demonstration, Behe (2001:689-690) simply shifted his attention to the complexity of the newly discovered system by itself, and at the same timestubbornly insisted that the assemblage of these precursors into the flagellum system is still impossible without the helping hand of a Designer (Behe, 2004:359).
 How "Irreducibly complex" structures form
One way in which "Irreducibly complex" structures could develop is via a process known as scaffolding, wherein a structure gains in complexity via duplication and mutation of parts, then parts are knocked out via mutations, leaving a structure with no direct linear development from the original, basic structure. Other paths by which irreducibly complex structures may form include cooption of parts from other structures. Both of these can be seen in the case of the bacterial flagellum, which includes many parts taken from a secretory pump.
Another is "function shift" or exaptation, which can also explain how irreducibly complex structures may evolve. During evolution, a feature may shift from one function to another-a classic example is the feathers of a bird. They originally evolved in dinosaurs as a way to keep warm, but birds then evolved to use them for flight. Half a wing might not be useful for flying, but it will still keep you warm. Our arms are another example-they were originally legs, but evolved into arms when we became bipedal.
Additionally, to assert that something is irreducibly complex is to assert that none of the parts could have provided a benefit by themselves. The more parts there are, the more impressive it is that all of them developed; however, this also means that there are more possibilities that have to be eliminated. For instance, if someone claims that there are ten parts to a particular irreducibly complex structure, then there are ten different possibilities for which one developed first. If even just one of them has a use that we are unaware of, then the structure is not irreducibly complex.
 See also
- Eye evolution, a good basic explanation of the subject.
- Response and explanation of the subject on EvoWiki
- Irreducible complexity and the scientific literature
- Irreducible complexity cut down to size, a nice video that refutes irreducible complexity.
- Rainbow Arch
- ↑ http://creationwiki.org/Irreducible_complexity
- ↑ See Wikipedia: Irreducible complexity (Emergence)
- ↑ Micheal Behe - Darwin's Black Box: The Biochemical Challenge to Evolution
- ↑ Björn Brembs - I CAN HAZ UR BEKTEERYA?
- ↑ Buchsbaum, R. Animals Without Backbones (Penguin 1958); vol.1, plate 64
- ↑ Scallop eyes
- ↑ Evolution IS a Blind Watchmaker: Video of a clock-'evolving' simulation
- ↑ 
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|Reductio ad absurdum|