[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: Some thoughts on AVES
----- Original Message -----
To: "Demetrios M Vital" <email@example.com>; <firstname.lastname@example.org>
Sent: Friday, November 02, 2001 2:00 PM
Subject: Re: Some thoughts on AVES
> In a message dated Fri, 2 Nov 2001 11:30:40 AM Eastern Standard Time,
Demetrios M Vital <email@example.com> (demetrios Vital) writes:
> > > Fortunately, I don't have to. We only have to classify the specimens
> > > actually discover. For this reason, abstract apomorphy-based
> > > 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
> > to fill),
> How so?<
If you're asking how "we" labor to fill the amount of knowledge we have, the
simple answer is by digging up new species. In the end though, it was a
vague statement that has no meat behind it.
> 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.<
Yes, but that ability exists for very few features. Classification can't
stop in the present.
> 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.<
That presumes that ability to pinpoint every adaptation to its exact gene
source. We can't do that reliably, now or with fossils.
> > We'd need a complete genomic understanding
> > of every individual in the population that speciates, which we can't
> > define, and then a complete understanding of the future heredity
> > 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.
That's a pretty arbitrary statement. Whose choice is it when that happens?
What percentage of the population must have the adaptation before it can be
used for a character-based system? Not to mention the difficulties of a
practical definition of "population"...
> 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_?<
Velociraptor didn't evolve into, or is an example of, birds. As to why
Confusciornis isn't used, I don't know. That's not an area that I can argue
for or against. And don't get me wrong, I know that every system has a huge
chunk of subjectivity to it, but some more than others. Tell me, are you
arguing for a hierarchical system, or just character-based classifications?