You (with all the rest of the Mere
>Creation crowd) seem to assume that Mike Behe has proved his case and has
>definitively shown that evolution cannot explain irreducible complexity.
I too have been concerned with the seemingly uncritical eagerness in which this
bandwagon is being jumped upon. It is reminiscent of the aftermath of
Johnson's book, Darwin On Trial.
While I applaud Behe for producing a thought-provoking tome, I have a problem
with a basic premise behind his thesis.
My problem with the model has to do with the presupposition that evolution
only works by fine-tuning the function of primordial structures. That is,
the idea that a mouse trap evolved from a primordial structure by gradual
improvement of mouse catching ability. This sounds like a microevolution
scenario. Behe's model, however, does not seem to account for the
possibility that a mousetrap could evolve from something that originally did
not function as a mouse trap, which seems more congruent with a
macroevolution scenario.
As i understand Behe's point, adding or subtracting from the component
parts of an irreducibly complex structure, such as a mousetrap, would leave
you with something other than a mousetrap. So how could natural selection
gradually fine-tune mouse catching ability if the primordial structure could
not catch a mouse? However, this begs the question of why couldn't a mouse
trap evolve from something with a different function? Why couldn't the
immediate progenitor of a mouse trap be a catapult, and the progenitor of a
catapult be something that moved passively, perhaps as a counterbalance
tool, etc?
Let's go to a biological example: I agree with Behe that it is hard to imagine
cilia evolving by fine-tuning of proto-cilia. Once you remove any of the
components of a cilia it ceases to have any cilia-like function. But is it
necessary to think that cilia must evolve in this way? Cilia are complex
cellular appendages with molecular motors that allow them
to wave and move cells through liquid, or move liquid past cells.
But, rather than evolving from something with similar function, why can't we
consider that cilia evolved from something that did not have cilia-like
function?
Suppose a primordial structure provided an early selective advantage because it
increased the surface area of the cell and facilitated nutrient uptake? This
primordial structure would not need all of the components of a cilia which
seems to take care of the problem of irreducible complexity of cilia.
The point of this exercise is that the concept of irreducible complexity
has an a priori constraint of functional similarity between
proto-structures and "final" structures that I am not sure is reasonable.
In other words, it seems that by irreducible complexity, Behe
means that complex structures are FUNCTIONALLY irreducible. If we ignore
the functional constraint, is Behe's view of evolution still reasonable?
Shalom,
Steve
____________________________________________________________
Steven S. Clark, Ph.D . Phone: 608/263-9137
Associate Professor FAX: 608/263-4226
Dept. of Human Oncology and Email: ssclark@facstaff.wisc.edu
UW Comprehensive Cancer Center
CSC K4-432
600 Highland Ave.
Madison, WI 53792
"Now how does one alter the charge on the niobium ball? 'Well at tha
t stage', said my friend, 'we spray it with positrons to increase the charge
or with electrons to decrease the charge.' From that day forth I've been a
scientific realist. So far as I'm concerned, if you can spray them then
they are real. Ian Hacking, Representing and Intervening, 1983
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