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Re: Some thoughts on cladistics



I haven't read Full House, so I have to go by your paraphrase.
<The point is that "evolutionary systematics" can,
additionally, declare species or higher groups as transitional between e. g.
reptiles and mammals, reptiles and birds or whatever. Here the cladistic
criticism is that this kind of transition is a complete artefact produced by
the recognition of paraphyletic groups, ...>

Birds are necessarily a paraphyletic group?

A system of classification starting from observation of easily
distinguished, numerous, and widespread modern groups is no more an
abstraction than any other approach.

<...at least for clades, phylogenetic systematics use the last common
ancestor instead of an archetype. The
ancestor at least existed :-)>

So, modern birds are an archetype, a non-existent (to our senses) model of
which living exemplars are only an imperfect image.  However, an
unidentifiable ancestor whose characters are being educed by a logical
argument is far more real.
This argument sounds a bit perverse, as I'm understanding it.

<However, these "basic body plans" (aka "Bauplan" [also a use of 'archetype'
in biology I did encounter]) have never been regarded as very serious by
those who drew them, and they haven't been used very much in
classification.>

There have been some apparently serious bauplan discussions here.

On the Plato/Aristotle distinction, the contrast is between speculative
results (Plato) against observation (Aristotle).  The (unoriginal) assertion
I made in the post to which you're responding is that Aristotle did not go
far enough.  Though he started from observation, he stopped experimenting
before assuring himself that he had enough observations.

He knew something about weight.  So he attempted to utilize that
understanding to determine what would happen if two similarly shaped metal
objects were dropped from a tower.  His logic was good, given his knowledge,
but his conclusion was outright wrong.
What was his error?  He used logic in place of direct observation.
So, let's propose a rule:  the further a hypothesis gets from direct
observation, and the fewer direct observations it's based on, the more
doubtful it should be considered.

The idea that a classification system should start with easily observed
modern groups seems comfortable to me in this context.

Simple, isn't it.  ;-)