Structuralism and evolutionary theory

Denyse posted some links to comments by Stuart Pivar
on Gould but one aspect caught my eye "structuralism".

I have done a little bit of research and structuralism
is an interesting concept which combines evolution
with morphogenesis. As many evolutionists and
philosphers (Ruse) have pointed out evolution is in
many ways constrained. It is constrained
mechanically, it is constrained by laws of physics,
it's constrained by laws of chemistry.

I am reading a book called "the plausibility of life"
by Kirschner and Gerhart which describes what they
call 'facilitated variation'which argues that while at
the genome level variation is 'random', at the
phenotype it is not.

Structuralism looks at the laws of physics to show how
the embryo 'self organizes', driven by laws of physics
and genetic information.

The work by Gordon from the University of Manitoba is
quite interesting
http://www.umanitoba.ca/faculties/medicine/radiology/stafflist/rgordon.html

While his main career focuses on radiology, Gordon has
been interested and involved in emergence for quite
some time and there are some interesting papers in his
collection.

Gordon shows that via gene duplication the
dimensionality of the genome increases, disputing thus
statements by IDCers (a discussion on ISCID's
brainstorms comes to mind...)
Variation and selection come to play on the copy of
the gene (or the original).Physics however is an
important process in emergence as well since to get
new capabilities (emergence) physics needs to be
represented so that selection has 'something to work
against'.

Structuralism argues that there is a genotype to
phenotype mapping and that this mapping happens via
genetics and physics.
This concept of self-emergence means that the organism
is both observer and designer.
This also resolves the question raised by for instance
Paley namely that design requires a designer.

And although people have also argued that emergence
requires an observer (god?),Gordon argues that the
designer and observer are part of the same system.
(see http://www.cs.bgu.ac.il/~sipper/emertest.html)

Gordon:

<quote>Artificial life research begins from the
premise that Alife subsumes real life. A criterion for
emergence in Alife has been formulated that, however,
excludes real life and postulates the need for a real
life Designer and an Observer. This in effect
nullifies the premise of Alife and takes us back to
the argument for God from design of Bishop Paley in
1802. An alternative is to realize that Alife could
include two properties: simulated organisms that both
design themselves and are the observers. Self-design
can come about via evolution in a population of mating
organisms, especially via mutations that are gene or
higher order duplications. Duplications permit novelty
while retaining previously attained functions. The
ability to observe can itself evolve, if its
construction process evolves. This may now be possible
to simulate, if new paradigms for embryogenesis, such
as positional information or differentiation waves,
prove accurate, or at least sufficiently robust to
construct a wide diversity of observational abilities.
The evolution of perception, however, may be limited
by the physics available to the Alife organisms, which
can come in three forms: simulated physics, real
physics accessible to robots, or "Cyberspace physics".
</quote>
The emergence of emergence: a critique of "design,
observation, surprise!" Riv Biol. 2000
May-Aug;93(2):349-56.

Rather than seeing structuralism as a replacement for
Darwinian theory, it complements it as it provides the
third prong of what is needed for evolution

1. A theory of natural selection
2. A theory of heredity
3. a theory of generation of variation.

Alan Love, in his review of:

Ron Amundson, The Changing Role of the Embryo in
Evolutionary Thought: Roots of Evo-Devo, Cambridge
University Press, 2005, 296pp, $75.00 (hbk), ISBN
0521806992.

writes
<quote>
Another of these principles is a criterion of
explanatory adequacy on evolutionary explanations
adhered to by structuralist biologists, the 'Causal
Completeness Principle': "In order to achieve a
modification in adult form, evolution must modify the
embryological processes responsible for that form.
Therefore an understanding of evolution requires an
understanding of development" (p. 176). This principle
underlies the structuralist conception of evolutionary
transitions, which is very different from that of
functionalists. Functionalists explain the process of
evolutionary change from one adult phenotype to
another via population processes such as natural
selection, which sorts genotypes and thereby alters
allele frequencies. Structuralists explain the process
of evolutionary change from one ontogeny to another
via developmental processes such as morphogenesis,
which can be altered in different ways to generate
novel phenotypes. The 'Causal Completeness Principle'
is irrelevant to the evolutionary explanations of
functionalists.</quote>
http://ndpr.nd.edu/review.cfm?id=4421

On Pandasthumb Andreas Bottaro comments

<quote>Structuralism is more about the development of
complex forms according to basic natural principles
and rules which are not genetically/epigenetically
encoded, but may reside in the structural organization
of the organism itself</quote>
http://www.pandasthumb.org/archives/2005/06/of_form_over_substance_a_review_of_sermonti.html

In "Defining Evolution" John Wilkins writes

<quote>Process structuralism: Some changes are biased
by their structural relations and form. The foundation
of process structuralism was laid by D'Arcy Thompson
(1917) and recently revived by Brian Goodwin (1994),
and others. Complex structures and systems are not
free to vary independent of their relationships with
other components of the complex.
</quote>
http://www.ncseweb.org/resources/rncse_content/vol21/1610_defining_evolution_12_30_1899.asp

Denyse makes some predictions
(http://post-darwinist.blogspot.com/2005/10/structuralism-growing-challenge-to.html)

<quote>

1. The structuralists will provide the best
explanation for the Cambrian explosion (when most of
the general types of life forms arose rather suddenly
525 million years ago).
</quote>

In fact, whether one wants to call it structuralist or
not, James Valentine (and many others) argue that hox
genes and the evolution of regulatory genes explains
much of the Cambrian explosion. In the end it seems
that it is a combination of genetics, variation,
selection and physical constraints that explain the
Cambrian explosion and undermine one of the icons of
ID.

<quote>2. However, some structures will elude a
structuralist explanation and be accepted as
irreducibly complex. That one goes to ID, along with
the origin of life.</quote>

In other words, our ignorance will guide us to infer
design rather than admit that we just don'tknow. Seems
that the role for ID is scientifically speaking
minimal or nonexistent.
Received on Sun Oct 30 08:56:57 2005