Circularity & testing.

Mark Garland MAGarland at AOL.COM
Mon Oct 21 09:26:36 CDT 1996


In a message dated 96-10-21 00:34:44 EDT, tdib at UMICH.EDU (Tom DiBenedetto)
writes:

<< You are obfuscating the point that the algorithm will display pattern when
 >there is no pattern to be displayed.

 What? Thats ridiculous. I think you mean "the algorithm will display
 a pattern generated by random data as well as a pattern generated by
 non-random data". Pattern is pattern; if random data generates a
 pattern, then it generates a pattern. Either the data aint random, or
 you have an artefact, but you cant deny it is a pattern. Once again,
 the intrpretation of the pattern is up to you, and will be heavily
 influenced by the decisions you made in putting together the
 data-set. >>

What's ridiculous is the typical interpretation of the pattern: the user of
the parsimony technique will publish a tree or trees based on these random
data and this will become accepted as the "true" or "best" phylogeny by other
systematists.  People who use parsimony (in systematics) assume that
evolution has produced any pattern they see in their data--and there is no
way to prove otherwise under parsimony (unless additional data reveal
"incongruencies").  The whole process is designed so that you'll find what
you're looking for--a pattern produced by phylogeny--whether it's there or
not.  Hey, it might work much of the time--but it might not, either.  How can
you know?

Mark A. Garland
Office of Environmental Services
Florida Department of Environmental Protection
3900 Commonwealth Boulevard, Mail Station 140
Tallahassee, Florida 32399-3000




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