Re: Philosophies for Character Ordering

["Jaime A. Headden" <qilongia@yahoo.com>]

David Marjanovic (david.marjanovic@gmx.at) wrote:

<Ordering only means to arrange the states of a character in a line. It
does not make any assumptions about which end of the line is the
plesiomorphy. This is for the outgroup to decide. If the outgroup has a
long tail, the ordered character will be equivalent to the assumption that
the tail gradually got shorter; if the outgroup has a short tail, the
ordered character will be equivalent to the assumption gradually got
longer. (Ignoring the possibility of reversals.)>

  As Mickey pointed out correctly, "ordering" argues that a taxon with
condition "2" must have "1" as well as "0", which is how it's treated in
the machine, and infers that the condition is progressive and in that
form, rather than in any other combination of acquisition or gradual loss.
A taxon that makes a "jump" from "0" to "2" is inferred to have gone
through stage "1" in its evolution (I made this point by bringing up where
a taxon can incorporate two vertebrae into the sacrum simultaneously
rather than one by one; the machine will interpret this the same way).
This is an intrinsic assumption of an unobserved process of evolution, and
appears to occur only through corrolary, and that can be done without
ordering any characters.

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


        
                
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