I wrote the following at another forum (a science forum, believe it or not) in which I was debating a proponent of 'intelligent' design. I borrowed heavily from Dr. Miller's "The Flagellum Unspun - The Collapse of Irreducible Complexity
, but used some more recent references for the TTSS & Flagellum discussion. I couldn't access some of the ones he cited:"
[T]he concept of irreducible complexity is not useless… It makes you think about the nature of systems and their origins. It doesn't necessarily makes you ignorant like Robison claims. It is also a tool of falsification for those who believe all biological systems have arisen through evolution without intelligent agents. It's a pitty that it comes from a man like Behe. Otherwise it may have gotten the proper attention it deserves.
It actually originates from Darwin, believe it or not. In his Origin of Species
(1859: 191), Darwin writes that if there existed an organ or organism that could not have been formed by "numerous, successive, slight modifications," the "theory [of evolution] would absolutely break down." Behe and others have obviously read this and used it as their weapon against science. The anti-science community called it 'irreducible complexity' and declared that there were systems that could not have evolved because the removal of just one part would cause the entire system to fail (Behe 1996; 2002). Behe, and other anti-science types, have cited the bacterial flagellum as one of the several systems that fit this mold.
Other systems cited by Behe include the vertebrate blood clotting cascade and eukaryotic cilium, but the bacterial flagellum is the most significant it would seem. Homologous to the basal region of the bacterial flagellum is a mechanism known as a type-III secretory system (TTSS), which transmits toxins to the cells of bacterial hosts. It's been demonstrated that the TTSS remains completely functional even with most of the parts of the flagellum itself. The research (Aizawa 2001; Briggs et al 2004; McNab 2004; Yonekura 2000) wasn't conducted with the desire to disprove so-called 'irreducible complexity,' but rather the need to better understand the nature of bacteria.
With regard to the cascade system of clotting blood, Behe says the following (1996, 84-86):
When an animal is cut, a protein called Hagemann factor (XII) sticks to the surface of cells near the wound. Bound Hagemann factor is then cleaved by a protein called HMK to yield activated Hagemann factor. Immediately the activated Hagemann factor converts another protein, called prekallikrein, to its active form, kallikrein. [...]none of the cascade proteins are used for anything except controlling the formation of a clot. Yet in the absence of any of the components, blood does not clot, and the system fails.
Factor XII, mentioned in the quote above, initiates the cascade. If Behe is correct, the absence of this protein would result in blood that doesn't clot. Yet, dolphins don't have it (Robinson, Kasting & Aggeler 1969). Their blood clots just fine. Neither factor XII nor prekallikrein are present in the puffer fish (Jiang & Doolittle 2003).
The concept of 'irreducible complexity' is, indeed, useless for offering any sort of logical explanation. Analogies of mousetraps and other machines are irrelevant. These are demonstrably designed
systems and are not
being suggested to be created by nature. Nature does, however, have its own "mouse traps" with systems of predator-prey organisms, but none have been demonstrated to be 'irreducibly' complex in any way. I challenge anyone here to show a natural system or organism that cannot operate without all
of its parts.
Aizawa, S.-I. (2001). Bacterial flagella and type III secretion systems, FEMS Microbiology Letters
, 202 (2), 157-164.
Behe, M. (1996). Darwin's Black Box
. New York: The Free Press.
Behe, M. (2002). The challenge of irreducible complexity. Natural History
111 (April), 74.
Briggs, L.J.; Davidge, J.A.; Wickstead, B.; Ginger, M.L.; Gull, K. (2004) More than one way to build a flagellum: comparative genomics of parasitic protozoa. Current Biology
, 14 (15), R611-R612.
Darwin, C. (1872). The Origin of Species (6th edition)
. London: Oxford University Press.
McNab, R. M. (2004). Type III flagellar protein export and flagellar assembly. Biochimica et Biophysica Acta (BBA) - Molecular Cell Research
1694 (1-3) 207-217.
Miller, K. R. (2002-2004). The Flagellum Unspun - The Collapse of Irreducible Complexity. In Ken Miller's Evolution Page (Evolution Resources). Retrieved 8106, from http://www.millerandlevine.com/km/ev...2/article.html
Jiang, Y. and Doolittle, R.F. (2003). The evolution of vertebrate blood coagulation as viewed from a comparison of puffer fish and sea squirt genomes
. Proceedings of the National Academy of Sciences
, 100 (13), 7527-7532.
Robinson, A. J., M. Kropatkin, and P. M. Aggeler (1969). Hagemann Factor (Factor XII) Deficiency in Marine Mammals. Science
, 166, 1420-1422.
Yonekura, K., S. Maki, D. G. Morgan, D. J. DeRosier, F.Vonderviszt, K.Imada, and K. Namba (2000). The Bacterial Flagellar Cap as the Rotary Promoter of Flagellin Self-Assembly, Science
, 290 (5499), 2148-2152.