Thomas Schlemmermeyer termites at USP.BR
Tue Aug 22 09:52:34 CDT 2000

Your problem has also been discussed in philosophy of experimentation.
Of course, it is difficult to do manipulative experiments with
phylogeny, but it is by no way impossible! You may think of these
homeotic mutations in Drosophila.

Another question that enters is the meaning of prediction.
The conventional, most conservative view which would be most
vulnerable to creationist attacks is that a theory must make a genuinely new
prediction which is then tested by a genuinely new experiment which
happens to be realized only after the prediction already was made.

It was shown however that such a strict temporal order between prediction and
experiment is by no way necessary. It is also possible to make predictions
which are tested by experiments or observations which happened already before
the prediction was made.

On (         Tue, 22 Aug 2000 08:41:30 +0100),         Zdenek Skala
<Zdenek.Skala at INCOMA.CZ> wrote:

>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

Thomas Schlemmermeyer, Ph-d. student, Sao Paulo, Brazil

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