Re: Cladobabble

[christopher brochu <cbrochu@fieldmuseum.org>]

>    Wow.  How many times have we been down this same road....?


Too many times, in my opinion.

[shortened - basically well-said stuff]


 The two really big problems with phylogenetic
>systematics as is it currently practiced is the inherent subjectivity of
>character
>selection and the extremely qualitative means by which those characters are
>described and thought of.


This, I agree, is a potential problem.  This is also why (to back down a
road I've been on multiple times here) one of the greatest strengths of a
phylogenetic analysis is its explicitness.  We can see precisely how big a
fool Tom Holtz is by looking at his matrix.  We can even put numbers on it
("Tom is an idiot xx percent of the time, and his foolish trees collapse
after only xx steps.").  The same is true for any phylogeneticist.  We have
no idea just how big a fool his predecessors were, because their
phylogenies were not based on anything we can actually review.


[shortened - again, more well-said stuff]

>
>There are people that love cladistics and there are people who hate it,
>but with a
>very few exceptions, no one is working in improving it.

I agreed with everything Josh said up to this statement.  Every issue of
_Systematic Biology_ and _Cladistics_ has at least one article improving
phylogenetic methodology (or at least claiming to do so); most of the
improvements with parsimony are in _Cladistics_, but not all of them.  In
fact, one of the most fundamental improvements to parsimony analysis (the
ratchet method for obtaining the complete set of MPT's) came about within
the past couple of years.

As for the problem of inexplicit character definitions - the only real
solution there is to have reviewers flag problems in submitted matrices.
And before someone cries out about the time necessary to do this, and how
no one really does it - in non-dinosaurian circles, this is standard
operating procedure.  My characters went through several cycles of review.
I know this is a dinosaur list, but phylogenetics is phylogenetics.

Another solution is to have each and every character figured in the text.



 I have been known to
>speak out against cladistics quite a bit, but what I am usually on about
>is the
>characters selection and description problem and the religious zeal by
>which some
>tote the methodology.  People are working on improving phylogenies, sure,
>but to
>my understanding very few paleontologists are working on the character
>problem.

Among dinosaur workers, perhaps.  Outside Dinosauria, no - this is a real
issue, and people certainly deal with it.  Go to the evolution/systematics
meeting sometime, and you'll see all kinds of people dealing with it in all
kinds of ways (some more violently than others).


chris





_________________________
Christopher A. Brochu
Department of Geology
Field Museum
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Chicago IL 60605

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