"Guy Hoelzer"  wrote in message
news:cfg2sc$n8t$1{at}darwin.ediacara.org...
> Greetings,
>
> I started a new thread here because this interesting (IMHO) subject arose in
> the "What is Life" thread.
>
> in article cfdfd8$2te5$1{at}darwin.ediacara.org, Chris Gordon-Smith at
> address{at}homepage.net wrote on 8/11/04 8:53 AM:
>
> > For the Baldwin effect to occur, the solution to the 'new'
problem has to be
> > within, or at least partly within, the repertoire of some or all of the
> > existing population.
>
> It was the excellent word "repertoire" that caught my
attention here.  This
> sentence seems to invoke the assumption that phenotypic repertoires are
> built up through natural selection.  Leaving aside neutral evolution
> arguments, I think this common view is mostly false.  In my view, the set of
> possibilities in the repertoire are imbued by the physics of complex
> adaptive systems.  IMHO natural selection does not create any of these
> possibilities; instead, I think the effects of natural selection generally
> work by constraining phenotypic plasticity.  It erects obstacles to
> phenotypic change that tend to threaten the long-term persistence of the
> lineage.

Does the genome act by digging channels or by constructing dams?

Dr. Hoelzer seems to have been inspired in his speculation by:
http://fsweb.berry.edu/academic/mans/jgraham/Emlen%20Chaos_1998.pdf

To be honest, this paper does not impress me very much.  My main complaint
is that it fails to make clear the distinction between phase space (where
the attractors live and within which trajectories are traced) and parameter
space (which controls and determines the geography of phase space).
Evolution consists of changes in the genome, which determines a point in
parameter space, which then interacts with the environment and the starting
state to determine a trajectory in phase space.

When viewed correctly, it is easy to see that changes in parameter space always
involve both kinds of changes in phase space - channel digging and dam
creation.  There are frequently Thom "catastrophes", with new attractors
appearing, or old ones disappearing or merging.  Evolutionary change involves
both kinds of changes in the attractor structure (as well as simple shifts of
the attractor).  There is no particular reason to focus on just one of these.

At the biochemical level, an enzyme is more in the nature of a channel than
a dam.  Nonetheless, progress in evolution is frequently made by modulating
the expression of an enzyme.  This is more dam-like.  Both processes occur.

At a philosophical level, I think that Hoelzer and also Emlen are most concerned
with placing biophysics and biochemistry into the central role, with genetics
relegated to a secondary role.  Certainly, no one would dispute that genetics
cannot take the organism to a place which is not allowed by the physics and
chemistry of the situation.  My analogy might be to an automobile.  The engine
is strictly physics and chemistry, as is the restriction on mobility forced
by the fact that the drive train is too close to the road.  But genetics is
still the driver and NS is still the navigator, riding shotgun and pointing
out the direction.
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