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Irreducible Complexity

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  • Irreducible Complexity

    This has come up, due to the fact that I am friends with many creationists. They often pose the idea that the existence of IC systems disproves evolution, and I wish to hear your take on it.

    I will the lay the argument out in premise form:

    P1 If irreducibly complex biological systems exist, then evolution is false.
    P2 The bacterial flagellum is an irreducibly complex biological system.
    C Therefore, evolution is false.

    I take issue with both of the premises.

    P1 I don't think it is the case that the existence of irreducibly complex systems disproves evolution out right. It only proves that the particular system which is claimed to be IC cannot have evolved. Perhaps, some intelligence played a role in instituting that particular biological system, but overall, evolution could still be a process which has occured, and still occurs.

    P2 My first issue, would be that just because you cannot take away a part of something and keep it's current function, doesn't necessarily mean that you cannot build it through incremental steps. For example, when building an arch. If you took any particular stone from the arch, it would collapse. But in the past, arches have been assmebled through incremental steps. A support beam is created to hold up the other stones during construction. We have also seen this in nature, outside of biology. A mound is formed, and the center is slowly eroded away, leaving but only the arch. So, it is conceivable that this bacterial flagellum has gone through this process sort of process, evolutionarily.

    My second issue, is that there is a likely evolutionary ancestor to the bacterial flagellum. It is called the type III secretion system. It is used to inject various fluids into some other organism. The proteins that compose it, however, are the same ones used to create the bacterial flagellum, but is missing others as well. This means, that if you take parts away from the bacterial flagellum, is still serves some function, and therefore is not IC. I am not saying that if you did it right now, it would do such, but it suggests in the past that the bacterial flagellum evolved from the type III secretion system.