cladism's greatest weakness

Tom DiBenedetto tdib at UMICH.EDU
Fri Sep 24 14:39:35 CDT 1999

Richard Zander wrote:

>You can't say that there is a world "out there" (implying some degree of
>inaccessibility) then say it is right here, something perceivable.

ButI didnt mean to imply that the world out there is in any sense
inaccesible, only that we can form mistaken ideas about it. Hence the
need for testing.

>I guess I'm a skeptic. Reminds me of another switch common in systematics: saying at
>the beginning of a paper that a reconstruction is being generated, then
>presenting a classification at the end of the paper.

What is the problem with that? Cladists believe in classifying in a
manner that mirrors the reconstruction.

>Let's compromise. There are collections in cabinets "out there" around the
>corner from my office. I perceive remembering perceiving them a bit ago.
>Notice the concious self-referencing which is highly PC and also good
>scientifically. I think there is an immense gulf between perceiving species
>and hierarchies "out there" and perceiving yourself construing models called
>species and heirarchies that help guide action. What happens is that unless,
>the distance between guess and by golly is accepted, realist systematicians
>begin to believe that the result of their analyses of samples is a direct
>and immediate perception of something "out there" or at least a close
>approximation of it.

Yes, we do hope that it can be a close approximation. Why else would we
be doing this?

>What evidence have I of this? The presentation of one cladogram per result.
>Optimization, yes, is a valuable tool, and is the best guide to action -
>given no loss upon failure. Is being wrong a loss to science? We have
>hundreds of published many of them are somewhat wrong? Very
>wrong? How do you tell the difference?

By examining the evidence, just like in all science. We do the best we
can with the evidence that we have. Then we try to find more evidence.
What more can you expect?

>A cladogram, in the presentation of
>poorly supported detail, is not a reconstruction, which requires
>considerable support in the form of reassurance that there are no reasonable
>alternatives. This is the realist burden and cladism's greatest weakness.

But porly supported cladograms are easily seen to be just that. So long
as one uses all available evidence, even a poorly supported cladogram
is state-of-the-art. And something to be improved upon by the next
worker. As in all sciences, we can only start with what has already
been learned, try to learn more, and train our students to do even more
after us.

>I believe there is good in modern systematics, but
>except for publications using Bayesian Markov chain Monte Carlo analysis,

Gee, I always thought the Bayesians had it all bass-ackwards, given
that the probability calculus was designed for a consideration of the
probabilities of *events*, not hypotheses. Probabilities of hypotheses
are not consistent with the calculus of probability. See both Edward's
book on Likelihood, and Popper's works on the scientific method for
critiques along these lines.

>present forms of phylogenetic analysis do not provide acceptable
>consideration of contrary hypotheses.

Do you think all scientists should abandon their preference for the
hypotheses that are most in accord with empirical data in favor of a
non-judgemental consideration of all alternatives?

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