2000 years of stasis

MAGarland at AOL.COM MAGarland at AOL.COM
Fri Feb 4 21:44:35 CST 2000

>  Mark
>  seemed to claim that cladistics is somehow essentialistic, because we dont
>  describe taxa anymore, but rather we "define" them. But this seems to fly
>  the face of the fact that it has been cladists who have been in the
>  forefront of the "diagnose vs. define" debates, and very much on the side
>  "diagnoses"! I mean, for example, read anything by Kluge in the past few
>  decades for long and extended philosophical arguments about why species and
>  taxa are individuals, not somehting that can be defined, but must be
>  diagnosed etc. etc. How on earth can cladistics be seen as essentialistic?

[disclaimer]  I am not a philosopher and do not understand half of what I
read. [end disclaimer]
Phylogenetic nomenclature attaches a definition, not a diagnosis, to each
name, and therefore to each taxon.  (See lots of papers by de Queiroz and
others about "phylogenetic *definition* of taxon names" or something
similar.) That definition boils down to the invocation of a common ancestor
and all of its descendents.

I would think attributes of the members of a group would be involved in any
diagnosis of a group.  But in phylogenetic nomenclature, attributes of the
named group--other than synapomorphies--are irrelevant. Are lists of
synapomorphies useful diagnoses?  Maybe, maybe not.  If I can't use that list
to identify something as a member of that group, then it isn't a diagnosis in
my book.

I haven't read much Kluge, but de Queiroz argued in 1994 (Syst. Biol.
43:497-510) that his "definitions" were not essentialistic.  I don't follow.
To me, if you are presuming to define, instead of describe, a taxon, you are
entering the world of essences.  You are leaving the world of appearances
(that is, attributes) and attempting to get to the unchanging soul of a
thing.  The essence of a phylogenetic taxon is the holy common ancestor and
all of its descendents.  And since we know that cladistic reconstructions can
never lead to falsehood, that definition of ancestor and descendents will be
unchanging and eternal (good for nomenclatural stability!).

Now maybe cladistic techniques themselves are not essentialistic, but
phylogenetic nomenclature is.

>  I think it is a rather strange perspective on essentialism to claim that
>  recognizing taxa as appertaining to real historical lineages is somehow to
>  be essentialistic.

Linnaeus recognized species and genera (which he *defined,* not described) as
real historical lineages created by God.  Yet people claim he was
essentialistic.  I'm just trying to be consistent.

>  I am also puzzeled by the remark "...I am looking at morphological
>  discontinuities in a limited part of the world, and putting morphologically
>  similar things into groups within groups. Sounds like folk biology to me...
>  Doesn't have a whole lot to do with identifying apomorphies and
>  plesiomorphies. "
>  Puzzeled because I constantly heard my cladist teachers referring to their
>  work as "erecting groups within groups based on [detailed] morphological
>  similarities and differences". Find a root on that system of groups within
>  groups and voila, you have identified apomorphies and plesiomorphies.

But what I'm looking at in the identification process is *any* characters I
can get my hands on.  I don't care whether they're apomorphies or
plesiomorphies.  Those categories are in a different world as far as I'm

If I create in my own mind a system of nested groups for identification
purposes, using any and all characters, will I have a phylogenetic
reconstruction?  I doubt it.

Mark A. Garland
Florida Department of Environmental Protection
2600 Blair Stone Road, Mail Station 2500
Tallahassee, Florida 32399

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