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Re: Cladistic Massive Retaliation
> >this may seem like a nitpicky point but cladistics makes arbitrary
> >in another way: it assigns NAME, which are for our convenience only.
> I fail to see why this is any more arbitrary than any other system,
> or even why this is flawed in any way. Please elaborate.
I wasn't attempting to make cladistics any MORE arbitrary, simply
that arbitrary judgements exist in cladistics. A clade may be a real
thing, but cladists have different ideas about WHICH clades are the genuine
ones (meaning, they make different judgemnts as to HOW common descent is
traced for an organism, based on abitrary interpretations of the data).
> A taxon based on common decent is much less arbitrary than either
> case. One can, make a paraphyletic taxon based on common decent.
> Why? What added value is there in burdening your taxonomy with
> trivia? Is today's zoologist so overworked that he cannot simply look and
> see which animals look superficially like which other animals?
You make it sound so simple. You might as well say "Is today's
paleontologist so overworked that he cannot simply look at the fossils
and see which animals are descended from other animals? Why do we
In any case, it isn't SUPERFICIAL similarities I am interested in.
You are forgetting that similarites can also result from analogy. Don't
cladists have to make this same distinction? You may not be aiming for
morphological similarities as the final goal, but you use them to determine
who is descended from who. I'm simply saying this information is useful
in and of itself in understanding evolution. Why shouldn't that
information be included in the taxonomy?
I think you overstate both the complications proposed by paraphyletic
groupings and the ease in identifying evolutionarily relevant differences.
What is wrong with arbitrary group divisions? If they do not
contradict the phylogeny (by creating POLYphyletic groups), and they
help understand the differences and similarities between groups AS A
RESULT OF EVOLUTIONARY CHANGES, why shouldn't these arbitrary grouping be
included? How are such changes "not real" just because they are a little
more difficult to identify?
All I am saying is that it is helpful for taxonomy to have a further
function in undrstanding evolutionary relationships and change than just
"who is descended from who".
> Morphological distance is *irrelevant* to phylogeny.
Morpholgical distance can be INDICATIVE of phylogeny, is the
distance is due to homology. They can also indicate WHY a phylogenetic
change took place. Including morphologies in a taxonomy can help the
paleontologist to understand why groups evolved the way it did, using
the morphological changes AND lines of descent as a guide. A taxonomy
that makes note of BOTH makes it easier for the paleontologist to
understand more about evolution than just who is descended from whom.
It provides perspective.
As an example: birds (read: avian dinosaurs) survived the K-T, while
dinosaurs (read: non-avian dinosaurs) did not. Why? Cladistics does not
make note of these differences, but a more traditional taxconomy might by
noting MORPHOLOGICAL differences between dinosaurs and birds (flight
modifications, feathers used for flight, endothermy?) which might have
bearing on WHY. (Don't start an endothermy debate based on this: I'm
just citing an example). What about the reptile-mammal transition?
Why shouldn't the morphological changes that might be indicitive of
different physiologies different directions in mammal evolution be made
note of in the taxonomy?
Doubtless, everyone will have different ideas about what
arbitrary groups to use, and changes will occur with time, but the
cladistics NONARBITRARY system is no less in flux. Considering that
cladograms change as new information comes in, I do not see how ARBITRARY
changes to this ARBITRARY system are any more problematic.