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Re: Archaeopteryx

On Tue, Jun 17, 2003 at 12:30:56AM +1000, Colin McHenry scripsit:
> From: "Graydon" <oak@uniserve.com>
> > What's a class, in quantifiable, testable terms?
> What is any taxonomic unit, in quantifiable, testable terms?  Species
> are not real, and yet they are the basic unit for all taxonomic
> systems.  Even under phylogenetic taxonomy, the taxa are not real -
> they are arbitary names positioned upon a particular phylogenetic
> hypothesis, as Oliver has pointed out.

Species certainly are real.

We can't comfortably *define* 'species', but there's a real sense in
which the lesser murlet is a different way of getting copies of genes
into the future than an ostrich.

And yes, phylogenetic taxa aren't 'real' in the pick-up-and-pound-on
-the-table sense; they *are* real in the 'testable hypothesis about the
pattern of descent in a group of organisms' sense.

> The only real level of organisation in nature is the organism (which
> is precisely what gets left out of most cladistic analyses, but that's
> a seperate argument).  EVERYTHING else is an abstract entity devised
> by us as a tool  that we use in our effort to understand the patterns
> we see in nature.


Common descent is real; it results in structure.  You can call that
structure organization if you want; if you are fussy about what
'organized' means, you don't have to, but the structure is there.

> > That reliance on the contents of specific heads, most commonly mentioned
> > hereabouts in genericonometer jokes, is one of the creationist
> > assumptions.
> Just because what is meant in the concept of the genus is subjective,
> doesn't mean that it is not a valid, usable conceptual tool in the context
> of a taxonomic system.  If most people can agree upon a subjective concept,
> then it has the potential to be a useful tool in communication.

It does.

It *can't* be science, though; science has to be independent of the
contents of any particular head.

> And get over the creationist thing, please.  Just because something is
> subjective, doesn't automatically make it creationist.  

The *idea* of 'equivalent broad categories of organism' has a long
creationist pedigree; it doesn't particularly well represent the
structure we've got from common descent, because the tree of life gets
periodically pruned by a madman with a chainsaw.

> Not even being really stupid is enough to make an idea 'creationist' -
> it needs to be far, far worse than that. :-).  Anyway, truly objective
> science is a myth.

Truly objective is something no one can be, but which can be
successively statistically approximated.  Just because we can't get
there is not a good reason not to try.

> As I stated earlier, and Oliver and Jean-Michel have emphasised, the main
> use of a taxonomic system is to facilitate communication of scientific
> ideas.  It's a tool, a means to an end, not a greater end in itself.


The end is to figure out that structure of descent, isn't it?

oak@uniserve.com | Uton we hycgan    hwaer we ham agen,
                 | ond thonne gedhencan    he we thider cumen.
                 |   -- The Seafarer, ll. 117-118.