Positivism vs Realism
tdib at UMICH.EDU
Sun Dec 14 18:19:30 CST 1997
James Francis Lyons-Weiler wrote:
>> gee, like maybe we should assume more modification even when we dont
>> see it, eh?
> Depends on how you "see it". If you "see" modification as those
> positioned on the parsimony tree, you are sure to underestimate
> the degree of modification sometimes.
so,,,,lets make up some more....give me your criterion by which to
declare that certain specific character matches are not homologs.....
>> The hypothesis tested is that the distributions coded in the matrix
>> are the result of descent. Logical violations of that are revealed as
> But isn't the backbone of the background knowlegde that
> characters are inherited? What does this do to c?
not in any particular way.I should have been a bit more precise. The
hypothesis tested is that the distributions in the matrix are the
result of descent in the specific pattern tested.
>> What gives
>> you the predictive power to claim that parsimony is underestimating
>> homoplasy, or that a particular synapomorphy is really an artifact
>> of something?
> I can't imagine a world where processes of evolution
> and taxon sampling and chaarcter sampling don't cause
> parsimony to (sometimes) underestimate homoplasy. How
> do the principles of evolutionary biology lead to the
> ridiculous conclusion that the processes of evolution will
> not render misleading data in specific cases???
Whoa,,,homoplasy IS misleading data,.We are not denying it, we are
> A major limitation of cladistics is the insistence that
> a synapomorphy is something that we get from a tree.
> It's not: they existed before humans evolved - before
> the term was coined. Hence, _apparent_ synapomorphy...
What silliness. That is like saying that a major limitation of modern
chemistry is the insistence that an element is something found in a
periodic table,,,in fact they are found in the real world. Trust me
on this James, all cladists understand that synapomorphies refer to
things that happened in the real world, often a long time ago.
>> How exactly do you propose to derive trees?
> With informative data that have survived critical tests.
Well cool, welcome to the club.
Tom DiBenedetto http://www-personal.umich.edu/~tdib/
Fish Division tdib at umich.edu
University of Michigan Museum of Zoology
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