Striking a balance, weighting and Cladistics

[Gabriel A. Eickhoff]

On Thu, 15 Feb 2001 18:35:49 -0800, Curtis Clark <jcclark at CSUPOMONA.EDU>
wrote:

>At 10:34 AM 2/15/01, Ken Kinman wrote:
>>    I don't how many nucleotide changes were involved in the evolution of
>>feathers, but it was a large number.  The above statement boggles my mind
>>and had my jaw dropping.
>>    Even individual nucleotides are of differential importance and will
>>someday be weighted routinely in some fashion.
>
>Ken, I'm more important than you are. Just ask any of my students who are
>hoping to get good grades at the end of the quarter. But I'm sure that in a
>different context, you are more important than I.

Curtis, ideed this is a clever analogy. But consider this twist on things.
Lets suppose that one of the students in your class is a dear, close fried
of Ken's. Now, I imagine that you Curtis are a very likeable guy, and
even with this students grade in mind, I think the student would still feel
that Ken is more important than you. Reason out also that this is ideed the
same context, just with a bias.

This is the type of thing that is happening every day in systematics. How
can we possibly put a weight on something? To do so would require not only
the most intricate and intimate understanding of that trait, but also all
the traits that you are weighting it against. This is unreasonable. But at
the same time it confounds us because we know that there needs to be a
scheme where this is possible and can happen. There needs to be a
standard...but currently, that is also unreasonable. We all reckon that it
needs to happen, that weighting must be done. The problem is not with that,
it that we just don't know how to do it...bias free.

So, I ask you, why do we continue to do it? In the name of "confidence" of
the characters weight? What is confidence anyway? Having never been to
Australia, I may easily reckon that all swans are white...infact I honestly
believe that I could go out an in an hour wrangle up a large group of people
who also believe that all swans are white. Who would be willing to swear my
life on it. While at the exact same time, I could do the same thing in
Australia, except with Black Swans.
So, confidence is only a function of what we know...or rather what we think
to know. What good is something we "think" we know, in science? Absolutely
no good at all. The first step is be able to look something in the face and
"know" it for what it is.

>The issue is context. Every homology is equally important in elucidating
>phylogeny. That fact is independent of their importance in any other
context.

Why then Curtis, if every homology is equally important, do we have
weighting?

Cheers-
-Gabe