Re: Underlying basis of classification (Was: Re Dinobirds)

[Philidor11@aol.com]

In a message dated 7/19/99 9:11:55 AM Eastern Daylight Time, 
cbrochu@fmppr.fmnh.org writes:

<<And the computer algorithm actually creates an unrooted network before we 
specify an ancestor - we really can't interpret ancestors on an unrooted 
network, since we don't know which way time runs on something like that.>>
and
<< The time axis is secondary to the network and imparts a sort of 
"directionality" that we can interpret as the result of evolution. >>

I see it.  
The only way an ancestor could not be created is if the diagram worked 
without descent, providing a circular constellation of animals based on 
certain specified traits.  The model of basal/derived traits implying closer 
to/farther from an ancestor is a separate, secondary analysis.  Presumably, 
if this model could not be successfully applied, then the observed 
association of the animals would be rejected.  Given the possibility of 
regression to more 'primitive' characters and the fact that the characters do 
not have to be combined for a functional purpose in a single animal, this 
secondary analysis is probably very forgiving.  
My difficulty in seeing this was the assertion in previous discussions that 
cladistics is a classification system based on evolution in preference to 
description.  From this it seemed to follow that any connection among animals 
must first be consistent with an evolutionary progression.  Methodologically, 
this is simply not true.  Shows you have to check your premises carefully in 
following an argument.

By the way, I  want to understand your point on the group:

<<(Amoeba(Oak Tree(Starfish, Tyrannosaurus)))
Where are the ancestors here?  Is the comma between the starfish and
teerex an ancestor?  The parenthesis between the oak and the metazoans?  
One could also express them with internested circles or boxes.>>

Leaving aside my initial feeling that you were saying that the oak tree was 
ancestral to tyrannosaurus, a relationship complicating family reunions, and 
that a single symbol can cover multifarious gangs of ancestors, I wonder if 
you want me to read the punctuation as 'the oak tree split off from a line 
leading to starfish before the line leading from starfish to Tyrannosaurus.'  
 I certainly see what you mean about internested circles or boxes, though my 
instinct is to try to turn each circle into part of a linear evolutionary 
narrative.
What is the accurate way to turn that statement into prose?
Thanks again!  This is fascinating.