The attitrion of taxonomic expertise

Tom DiBenedetto tdib at UMICH.EDU
Fri Oct 18 11:48:06 CDT 1996

On Fri, 18 Oct 1996 09:19:36 -0700, James Lyons-Weiler wrote:

re. synapomorphies and circularity
>The "best fit" part is circular; the data that are used to choose the tree
>that provides the best fit are used to test homology (the data).

Sorry, but I think the circularity is in your head, not in the method
:).  The hypotheses are combined into the pattern with the least
incongruence. That is what we call a "best fit". Hypotheses which are
incongruent are made to fit the best pattern by dissecting them into
as many congruent parts as necessary to fit the pattern, All of this
is done within the expectation that true homologies are congruent.
The data are not used to find a best fit and then that best fit used
to test the data. There is only one step; the fitting process IS the
test of the homologies under the expectation of congruence.

Tom DiBenedetto
Fish Division
Museum of Zoology
University of Michigan

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