Zdenek Skala Zdenek.Skala at INCOMA.CZ
Tue Aug 22 08:41:30 CDT 2000

John Grehan wrote:
>If direct observation is taken for granted then there is no need for
>"theory" of any kind - whether a theory of evolution, of relativity, of
>biochmeistry etc. Everything is observable. Yet much of scientific
>"knowledge" comprises conceptual models of reality. That these
>models are
>effective in predicting factual events not already known (e.g.
>nuclear explostions) renders them useful - regardless of whether
>anyone may view them as true representations of reality.
Probably I was not specific enough. The observations are of course
not sufficient to science but they are necessary to it - I mean
"observation" in a rather wide sense. The problem (in my opinion)
is, that "traces of evolution" are open to different explanatory
models (several phylogenetic models, at least) and under all of
them the data pattern give some sense. Very similar
"pattern/process" problems are well known in community ecology
(one community pattern can be created by several different
processes) and the prevailing meaning is, that IF they can be
solved, it can be done only by manipulation experiments. Since the
phylogenetic data set is "closed" by being a historical one, we
cannot design such experiments (and so make really new
observations). Strictly said, we can see "fossils" but do not know
what they represent (in terms of phylogenetic events). We can
make only different equally plausible models about them where
"plausibility" refers more to the scientific "esthetics" than to what is
believed to be scientific standards.

John Grehan:
>In terms of evolutionary theory a common criterion for usefulness
>is prediction of one form or another.
Well, but this is about congruence of the data, not about the
evolution. Even within evolutionary theory many congruences exist
that are not phylogenetic (I think that even creationists would be
able to construct a model with a high predictive power - remember
Linnaeus). On the other side, different phylogenetic models can be
found as having high predictive power for different purposes. I would
quote here the often discussed incongruence between the
phylogenies inferred from molecular vs. morphologic data.
] Zdenek Skala
] e-mail:
] skala at incoma.cz

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