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Tom DiBenedetto tdib at UMICH.EDU
Tue Jan 26 16:00:36 CST 1999


Thomas Schlemmermeyer wrote:

>>I think there is more to it than that. Simplicity is inherint in the scientific
>>approach. If one does not attempt to formulate the simplest explanation, then
>>one might as well rest content with a separate explanation for each
>>phenomenon (the most complex explanation); i.e. no science.

>I would not agree with that. Especially biologists should recognize that their
>science is of quite idiosyncratic nature. Why were the dinosauros extinguished?
>Why are there no leaf-cutter ants in Africa? and so on.
>The diversity of life is so amazing and overwhelming that often simplicity
>makes place for complexity.

The simplicity standard inherint in parsimony is applied only to the range of possible explanations for a given set of
phenomena. It does not compel you to ignore the complexity that exists; it merely states that you should not
postulate complexity unnecessarily. If it is necessary to postulate complexity in order to explain something, then go
right ahead. That would not violate parsimony.

>In the beginning of a scientific paradigm there often is an elegant metaphor,
>a simple phrase which enlightens and entrances its followers. Having past by
>some decades, one discovers that maybe the anterior model or a third not even
>thought out paradigm may find some use as well.

Sure,,once again, parsimony is applied only to alternatives that explain equal amounts of data.

>Another cause which may lead to some conflict between simpler and more complex
>models is the level of organization one looks at.
>Simple parsimony models were developped by systematists, the level of
>organization would be, in this case, the whole organism. That all goes back to
>Aristotle and his book about the parts of animals.
>Evolution, ultimately, should be understood however, at the level of
>populations and gene frequencies. This may be a field where one feels nearer,
>in terms of thinking, to Felsenstein.

I think that Felsensteins work is inherintly about explaining genetic evolution, and that therefore he will need to
develop ever-more complex models of that evolution. I have no problem with that; it does not violate any parsimony
principle that I understand. Complexity in a model is good, if you are trying to describe a complex reality. Parsimony
only cautions you to not make your model more complex than it needs to be. My dispute with Felsenstein is that he is
foccusing his efforts on estimating the phylogenetic pattern with his models, and I think that is putting the cart before
the horse. I think he should be using the phylogenies (for any given group) developed by those who look at all
available evidence (morphology, behavior, genes etc) and then trying to model the evolution on that tree (as others
do who study character evolution).

>> Evolutionary theory must explain our
>>discoveries of homology, they are not the source of it.

>Yes and No. This is a very complicated problem I think.

yes




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