Ashlock was treated badly
tdib at OCEANCONSERVANCY.ORG
Tue Jan 8 09:47:48 CST 2002
From: Ken Kinman
it strikes me as odd that Ashlock's attempt at precision should be
regarded as illogical or unwarranted, and yet precision suddenly becomes
important when cladists want to distinguish "adjacency" and "directionality"
of character states. In most fields of human endeavour, "ordering"
encompasses both adjacency and directionality.
Actually I think that ordering does not necessarily encompass
directionality. My email program orders my emails by reference to the time
and date that they were recieved. That is ordering. I can then click on the
little bar at the top of the window and put the most recent email at the top
of the list, or, by clicking again, put the oldest at the top. That is
imposing directionality. I dont think it is anything peculiar to cladists to
separate out discrete steps in one's methodology. It is, I think, part of
the natural progress in any rational endeavor.
As I mentioned before, Ashlock's proposal was not an attempt at precision;
by the time he made his proposal, the three relevant categories
(poly,para,mono) were defined as precisely as they are now. His proposal was
to simply substitute holo- for mono- and to use mono- as a general term
encompassing both paraphyly and "holophyly". So it was an attempt at
protecting and promoting a generalization, not adding precision. And it was
opposed because the generalization is useless. If there is a useful
generalization to be made by combining two of the three categories, then
surely it would be a concept that encompasses poly- and paraphyly, for they
both share the characterisitic of being groupings that do not reflect our
best inference to the true historical pattern of taxic divergence.
Instead of fighting these little proxy battles, it might be helpful to
simply face up to the simple issue that divides us. Your logic, and
Ashlock's is perefectly fine, given your premises, as is cladistic logic
given its premises. The underlying dispute is simply the (very) old issue of
whether or not the scientific classification of life should be aligned with
our understanding of the historical pattern of taxic divergence - or not.
If you accept this criterion, as most have, then paraphyletic groups are
simply mistakes, and it must be a central mission of systematics to correct
them. Monophyly, sensu Ashlock, is meaningless. Hennig's precise definition
of the three concepts, rooted in the nature of the evidence that underlies
the groups (apomorphy-monophyly, plesiomorphy-paraphyly,
convergence-polyphyly) is perfectly logical and clear, and a successful base
for a coherent classificatory method.
If you do not accept that classification should reflect the historical
branching pattern, then you could come up with any number of logically
coherent methodologies based on whatever particular premises you choose.
That seems to be your position. Arguing the internal logic of one system by
making reference to the premises of another seems rather besides the point.
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