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Re: Some thoughts on AVES
In a message dated Fri, 2 Nov 2001 11:30:40 AM Eastern Standard Time, Demetrios
M Vital <firstname.lastname@example.org> (demetrios Vital) writes:
> > Fortunately, I don't have to. We only have to classify the specimens we
> > actually discover. For this reason, abstract apomorphy-based definitions
> > like the one I gave do not bother me overly much.
> Again, not only are you relying on a lack of knowledge (which we all labor
> to fill),
> but are setting up a system which inherently has limitations.
> One of these limitations is the fact that you can only work with fossil
Not at all. If I wanted to define a group as all descendants of the first
individual to carry the feline wire-hair gene (the first occurrence of which is
historically documented), I would be free to do so. It would be an odd thing
to do, but I could do it, in principle.
> > Not necessarily (see above). And besides, any adaptation, if defined
> > strictly enough, must indeed have been acquired overnight.
> I don't know if that's true.
I do. Any given heritable feature (again, if narrowly enough defined) will
have a first occurrence, whether it is due to a novel mutation or to a novel
shuffling of genes.
> We'd need a complete genomic understanding
> of every individual in the population that speciates, which we can't even
> define, and then a complete understanding of the future heredity patterns
> of those individuals. That's not possible.
Yes, and therefore it would be unwise to name a group based on such a feature
until it had fixed itself in a population.
> And aside from all the problems listed above, the system is _still_ more
> arbitrary that phylogenetic taxonomy!
Wrong. Defining Mammalia based on auditory ossicles is no more arbitrary than
defining Aves based on _Archaeopteryx_ and _Passer_. Why not use
_Confuciusornis_? Why not _Velociraptor_?