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From: gallagher@husc4.UUCP
Newsgroups: sci.bio
Subject: Re: Comment on punctuated equilibria
Message-ID: <1634@husc6.UUCP>
Date: Fri, 10-Apr-87 13:13:12 EST
Article-I.D.: husc6.1634
Posted: Fri Apr 10 13:13:12 1987
Date-Received: Sat, 11-Apr-87 17:31:44 EST
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Reply-To: gallagher@husc4.UUCP (paul gallagher)
Organization: Harvard Univ. Science Center
Lines: 41

I've found out in the past 24 hours that there are indeed evolutionary
theories which assign no role or almost no role to natural selection -
so I owe Mr. Strickling an apology.

Specifically, Daniel Brooks and E.O. Wiley ("Evolution as an Entropic
Phenomenon") and Peter Saunders and Mae-wan Ho ("The Complexity of
Organisms" - both in J.W. Pollard, Evolutionary Theory: Paths into the
Future) emphasize that the theory of natural selection, because it is
an optimization theory, is inadequate to explain the complexity of
organisms and the fact that the origin of species and the production
of diversity are time-dependent and thus irreversible phenomena.  Hence,
they use the principles of non-equilibrium thermodynamics to model
evolution and embryological development as irreversible entropic
processes characterized by the increase of information complexity.
In this framework, the existence of convergence - which I cited as
proof that natural selection must be a force in evolution - appears
"because variation is constrained by the deterministic factors in the
information systems of organisms" - the same changes appear in
different organisms because these changes correspond to a minimal
increase in complexity...

Along similar lines, Brian Goodwin ("Changing from an evolutionary to
a generative paradigm in biology" in the same book as the above)
argues against the historical  emphasis of evolutionary biology.  An
adequate answer to the question, "why does this dog have a tail"
is not "because its parents had a tail".  He emphasizes morphogenetic
fields - embryological regions which have the ability to generate
forms.  Rather than being completely controlled by inherited genetic 
elements, they are structures guided by generative principles which
direct spatial and temporal organization.  Each morphogenetic field
has the potential of creating a great variety of forms, "because
each morphogenetic field is described by equations with many solutions
which define the set of morphological possibilities."  Evolution,
even though it involves changes in genes and the environment, thus
is to be understood as a change from one solution of the morphogenetic
field equations to another.

In both these theories, natural selection is thus entirely peripheral
to the understanding of evolution.

Paul G.