From: Tim Ikeda (firstname.lastname@example.org)
Date: Tue Sep 10 2002 - 20:59:47 EDT
>I believe the flagella was used originally in the Black Box because it had
>a very direct analogy to mechanical swimming devices and thus could be
>clearly seen as an interworking set of components that function all for
>one purpose or not at all.
Yes. I remember that this system was used for illustrating the concept
of irreducible complexity. But as a test case for determining whether
IC systems can evolve it has some problems. The first is that the
organism or class of organisms which later gave rise to bacteria with
flagella is not well defined. So knowing what components were around in
the immediate pre-flagellar progenitor is extremely difficult to determine
(actually it's currently impossible). Second, the acquisition of the
flagellum likely happened roughly two billion years ago, which seriously
reduces the odds that any sequence homologies will survive (It can happen but
it's probably extremely rare). The effects of time in conjunction with
strong, optimizing selection adds to the difficulty. Basically, as a means
of directly addressing the question of whether IC systems are accessible
to evolution, the bacterial flagellum does not strike me as an experimentally
This is not to say that people won't try to figure out its history,
either from creationist or evolutionary perspectives, but I just
don't think we have anywhere near enough information to reach anything
like a reasonable conclusion. Like the RNA world hypotheses, I think
the study might be an interesting intellectual diversion, but not likely
to acheive strong results.
>Regardless, wasn't the cilium mentioned in the Black Box, and isn't the
>cilium more "modern" in evolution, yet far more complex?
Yes, cilia were mentioned in Behe's book. I do not believe that they could
be considered more "complex" than flagella, as there can be fewer components
involved. Note however that some cilia are probably in the neighborhood of
about billion+ years old. Cilia could be interesting from the perspective
that they do exist in different forms in different species and therefore
it may be possible to examine a relatively "new" structure with regard
to possible pre- and post-emergent states. That is, in some cases it may
be possible to determine what components were available in the ancestral
state and compare this to an organism carrying a newer version of the system.
Components of cilia (and their closely related proteins) and differences in
how they operate in other cell functions might also be an interesting study.
>What systems do you propose are more modern than the flagella that would be
>easier to work out due to the evidence available about their formation?
To a certain degree I had hoped that biologists such a Behe would have
already made some suggestions. Picking the correct model system to
address a particular question is often the most important step in doing
research. Ideally, you work with systems which are likely to provide
the best, most conclusive answers. This often makes the difference between
four years and a Ph.D. vs. eight years and a M.S. Because the question is:
"can IC systems arise in evolution?", I believe it is best to study a system
in which the pre- and post-IC emergence data is most readily available. In
practice this means working with systems that have most recently appeared
and for which we have good parent and sibling data for comparison.
Recall also that Mike Behe described the blood clotting cascade and parts of
the mammalian immune system as examples of IC systems. Many of the components
of these systems post-date the origin of cilia by perhaps a billion years. But
I'm not sure why they just haven't received as much attention from Dembski and
others. If any mathematical evaluation of evolutionary probabilities is likely
to succeed, it can only be done on the most recently emerged systems, not
ones billions of years old. Other systems that have more recently emerged in
their current forms could likely be found among systems that involve host/
parasite or symbiote/host interactions, transcriptional regulatory systems
in closely related organisms (e.g. differences in regulation of the same
operons in bacteria such as E.coli and S.typhimurium - or even between
strains of the same species), and other areas where co-evolution and "arms
races" may drive rapid changes in key systems. Functions need not have dozen
of components: A basic IC system needs only two.
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