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More Cladistic Stuff [Part 1]



[I'll tolerate some drift here for the same reason I accept messages
 on heat transfer computations, but I can't let this go on forever.
 Please try to keep in mind that this list is about dinosaurs not
 cladistics! -- MR ]

Part one in a series...
------------Norm King wrote:
>You see, I haven't been completely assassinated yet--

        If I had wanted to assassinate you, you wouldn't be e-mailing now... :)

>I think, however, if a tally could be made, we would find that
>morphological distance DOES reflect phylogeny most of the time.  And, if
>you are interested in what physically exists in the world, you will use
>morphological distance to find out.

        Morphological distance, as in shared synapomorphyies, certain help
us to discern phylogeny.  Once the determination of phyloegny is made,
morphological distance adds no useful information about the phylogeny.
However, it does not point to clear groupings, nor does it show us what
"physically exists in the world", and I eagerly anticipate teh inevitable
clarification of your point.

>Animals and plants are everyday objects that we can see all around us.

        Yes, but *groupings* of animals and plants based on diagnostic
definitions and paraphyly are *not* real entities.

>But cladists define things that
>have no concrete reality, and then say that _only_ those things are real.

        Is there another cladist out ther who will clarify this point?
Obviously, I am doing an inadequate job of explaining why phylogenetic taxa
are real entities.  NK, please re-read my last couple points, I don't want
to clutter the list yet again.
        
>This reminds me of an Aristotelian ideal that we can only envision,
>and then hope to find out how it is manifested, albeit imperfectly,
>in the real world.

        Can we ever observe phylogeny in action?  No.  Please reread my
posts.  If you still do not understand why a phylogenetic taxon is real, see
Gauthier and DeQuieroz 1990.

>So we don't rename the ancestors, we rename the descendants, calling
>them birds.  Even though the ancestor-descendant chain is complete,
>there was a major discontinuity in the history of life at that
>transition.

        Bufallo chips!  The "History of Life" as you call it is not a real
thing.  There is no Ultimate Historian judging which event is more important
than another.  There is only evolution, deaf, dumb, and blind.  Birds are no
more phylogenetically distant from other dinosaurs than are dromaeosaurs,
they just have different adaptions.

>You can't _define_ it away!  What's more, it is morphological
>distance that allows us to recognize this _real_ discontinuity.

        No one is "defining away" a major event.  We grace that event with
the creation of a new taxon just like traditional taxonomy.  What we do not
do is redefine the ancestral group because of that event.  Phylogenetic
taxonomy covers the novelty of birds in an objective and even-handed way, by
recongizing a new taxon.  The phylogenetic taxonomicist does not re-arrange
ranks (which are purely subjective, and have no basis in phylogney, and no
quantifyable, discernable basis in objective reality), nor does he redefine
the more inclusive clade, or remove the less inclusive from the more
inclusive, because this would violate the basic tenant that taxonomy should
represent phylogeny, and thus consist of paraphyletic groups.  The
phylogenetic relationship of birds and other dinosaurs is much better
represented by this system.  I challenge you to provide evidence that a
non-phylogenetic taxonomy can better represent the phylogeny.

>There is clearly a conflict of value systems here, which is a

        The value systems can be summarized in terms of what you want out of
your taxonomy:
        A card catalog, ala phenetics, like alphabetical order, which
emphasizes ease of fitting an object into you classification.
        An objective system, like the cladistics, or rock classification
(well, ok, it approaches this...), which is based on an objective reality
and involves incorporation of the system units into discussion of the main
paradigm of the science in question.
        An half-keystered cross between the two, attempting to fit
subjective groups into a quasi-objective structure in some sort of attemt to
combine objective reality with ease of classification.

        In short, it is the Beverly Hills principle.

        Wagner
+--------------------------------------------------------------------------+
| Jonathan R. Wagner                    "You can clade if you want to,     |
| Department of Geosciences              You can leave your friends behind |
| Texas Tech University                  Because your friends don't clade  |
| Lubbock, TX 79409                               and if they don't clade, |
|       *** wagner@ttu.edu ***           Then they're no friends of mine." |
|           Web Page:  http://faraday.clas.virginia.edu/~jrw6f             |
+--------------------------------------------------------------------------+