Re: Addressing Scientific Reductionism

Robert Kolker wrote:

dkomo wrote:

Moreover, in a book I've just recently slogged through, _The
Plausibility of Life_, such modular organization has been strongly
selected by evolution because it greatly facilitates the process of
viable phenotypic variation. Organisms are modular because they can
evolve more easily if they are. A small amount of genetic change can
result in big changes in organism characteristics. No need for
Darwinian gradualism.

Now that is quite fascinating. That could very well account for
punctuated equilbrium. It is interesting to note there is much more to
(possible) evolutionary mechanisms than the sculptoring and culling done
by natural selection.

I am beginning to understand why thinkers like Dennett consider the
theory of evolution the greatest thing since sliced whitebread.

If you think about it for a minute, you will quickly come to the
conclusion that such a systems design is inevitable. The notion that
"one gene encodes one trait" was completely dispensed with by 1945
(although the idea remains implicit in mathematical genetics). Rather,
by the 1930's, it was becoming obvious that any complex character in the
phenotype was the result of the expression of a significant portion of
the genome.

If that's so, the question then becomes: "how do you evolve such a
structure?" If the interaction matrix between gene products and their
affected traits is such that everything affects everything, evolution
becomes impossible. The entire design becomes a house of cards. You
can't change any bit of code without affecting the entire organism.

The evolution of modular design ("organ-ization") is the only way out,
and it's advantages have been discovered independently by human
engineers and nature, albeit several billion years displaced in time.

Pleiotropy is the inevitable consequence of highly interactive systems.
Pleiotropic effects ? in any complex system ? are intrinsically
minimized by modular partitioning of the subprocesses. And evolution, as
an adaptive process, has just as clearly discovered the values attendant
to modular code and partitioned behaviors. Indeed, such structural
partitioning is the mechanism that allows the common phenomenon of
"mosaic evolution," the evolutionary process where one part of the body
(such as mandibular morphologies or gut chemistries) are allowed to
rapidly change in response to new evolutionary pressures while other
organs (such as the eyes or feet) remain relatively unmodified.

Engineers who work on very complex systems tend to define two qualities
as attributes of complexity: "coupling" and "cohesion." Cohesion is a
measure (somehow calculated) of how closely the internal parts that make
up a module belong together when seen from different perspectives.

Coupling, in contrast, measures how much the submodules interact. Good
structuring and clever systems design works to partition complex systems
into minimally interacting modules by reducing the implicit complexity
by minimizing pleiotropic interactions between the subparts.

In that regard, the following is what Microsoft writes on the subject.
Although Microsoft is writing this text in regards to the costs of
software maintenance and the speed of evolving code, the same morals
apply just as specifically to germline DNA:

======================================================

"Two pieces of code are coupled if there is a high probability that
changing one piece will require changing the other. Because of its
complexity, software is highly susceptible to coupling. Coupling can be
quantified by a dependence matrix containing the probability that module
A will have to change in response to a change in module B. High
probabilities are bad because an upgrade can have a cascade effect of
changes throughout the system, and the duration of this cascade is
exponential in the probability of coupling. Thus we expect that coupling
correlates with the cost of maintenance, and indeed Darrel Ince cites
confirming studies. Coupling is essentially the opposite of modularity
and must be minimized for evolutionary prototyping to be cost-efficient.

"A global technique to reduce coupling is to distribute knowledge on a
"need-to-know" basis. That is, module A doesn't know about module B
unless B has an immediate role in A's job. This is the main reason to
avoid sprawling global namespaces. Furthermore, what A knows about B is
limited to the role that B has to A. This is the motivation behind
encapsulation and multiple interfaces."

-- http://research.microsoft.com/~minka/patterns/intro2.html

======================================================

Wirt Atmar

.

Relevant Pages

  • Re: Addressing Scientific Reductionism
    ... such modular organization has been strongly ... theory of evolution the greatest thing since sliced whitebread. ... can't change any bit of code without affecting the entire organism. ... but that is not an argument using natural selection at the organism ...
    (sci.bio.evolution)
  • Re: Addressing Scientific Reductionism
    ... such modular organization has been strongly ... theory of evolution the greatest thing since sliced whitebread. ... can't change any bit of code without affecting the entire organism. ... but that is not an argument using natural selection at the organism ...
    (sci.bio.evolution)
  • Re: Addressing Scientific Reductionism
    ... such modular organization has been strongly ... theory of evolution the greatest thing since sliced whitebread. ... can't change any bit of code without affecting the entire organism. ... but that is not an argument using natural selection at the organism ...
    (sci.bio.evolution)
  • Re: Results of the Great Evolutionist/ID Debate Thread
    ... about how light detecting cells could have sprung up in the first ... (not the eye itself, which is what was being discussed in the above, ... Acting like evolution is the only logical way to view the fact that ... behavior and processes of the organism. ...
    (talk.origins)
  • Re: specialization momentum
    ... The Concept of Momentum of Specialization ... Linearity of evolution of the whole organism is one element. ... As situational filters change in a milieu in some ways and remain somewhat ...
    (sci.bio.evolution)
Loading