From: bivalve (bivalve@mail.davidson.alumlink.com)
Date: Tue Nov 05 2002 - 19:08:05 EST
>Some time ago, on this list, Behe's and Dembski's use of the
>bacterial flagellum as a system of irreducible complexity was
>dismissed with the claim that it probably evolved out of the type
>III protein secretion system. I tried to check the evidence
>available to support this claim.<
[useful detailed comparison deleted]
>In any case, the similarities between flagellum and type III export
>are very restricted, making any derivation claim highly speculative.
>Whether the sequence similarities which do exist derive from
>divergence from common ancestral genes or from functional
>convergences remains equally uncertain.<
>Does this situation "explain" the flagellum and demonstrate that it
>is not "irreducibly complex"? I doubt it. The claim remains to be
>substantiated.<
The similarities between parts of the flagellum and type III systems
certainly does not provide a full explanation of the origin of the
flagellum. However, they do contradict a basic assumption of
identification of irreducible complexity, namely the assertion that
the parts are only useful as components of the whole system and could
not be gradually assembled piecemeal. Instead, we have a subunit
that can be used as a component of multiple systems. Thus, all the
parts of a flagellum did not have to be assembled all at once.
Thus, ID is not disproven, but it is not supported, either.
Dr. David Campbell
Old Seashells
University of Alabama
Biodiversity & Systematics
Dept. Biological Sciences
Box 870345
Tuscaloosa, AL 35487 USA
bivalve@mail.davidson.alumlink.com
That is Uncle Joe, taken in the masonic regalia of a Grand Exalted
Periwinkle of the Mystic Order of Whelks-P.G. Wodehouse, Romance at
Droitgate Spa
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