The attitrion of taxonomic expertise

James Lyons-Weiler weiler at ERS.UNR.EDU
Thu Oct 17 08:35:23 CDT 1996


On Thu, 17 Oct 1996, Alan Harvey wrote:

[in response to my post on how statistics have aided molecules]

>         I disagree with the causality here. Molecules overran morphology
> long before the sophisticated statistical techniques arrived on the scene.
> It's my impression that these techniques began to appear when the molecular
> folks realized they needed to be able to explain unusual (i.e., highly
> discordant with morphology) results, and could neither simply claim
> inherent superiority of molecular data nor re-examine their characters in
> the manner of a morphologist.

My point is that if statistical techniques such as maximum likelihood were
not developed, the criterion of discordance would apply to both
morphological and molecular data.  Because the tecniques apply to
molecules, the fault of discordance went to the untested partition of the
data, namely, morphology.


> produces an odd result, I can identify the specific characters that support
> the odd branches, and evaluate those characters (or any other, for that
> matter) using either a priori or a posteriori criteria, and I can
> re-examine the characters on the organisms with respect to homologies, etc.
>
It would be nice to not have to rely on the tree to tell you about the
quality of the data, because it smacks of circularity.  A recent
perspective on reciprocal illumination is tied to suspicion of inductive
reasoning, and preference is given measures of true probabilistic support,
which induction simply cannot provide.

I, too, wish to avoid molecules vs. morphology (as Alan stated last post),
because I think it a non-sequitur.  Those arguments rely on
generalizations, which don't hold.  Waht simply matters is a comparison in
specific instances.  For me, the path leads to questions of information
and noise content, which are directly observable in every case.

(Point of clarification; I didn't raise the tree of life symposium; I'm
not an iconoclast. I was referring to a point that I raised during the
symposium.  My fault for not yet having coffee).

James Lyons-Weiler

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