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Re: Linnean Classification and Creationism



Tom Holtz writes:

"All monophyletic taxa are real taxa, if we accept that evolution
by descent has occurred... As such, monophyletic lineages exist,
and thus clades exist."

I have a problem with the word "exist," which was first brought
home to me when I discussed the idea of "species" with a cladist
(before my boycott of the sci.bio.paleontology newsgroup). I
explained that any species that is ancestral to any other species
is by definition a paraphyletic taxon, because it no longer
includes all its descendants, and that for cladists to allow
species, but not other taxa, to speciate is inconsistent. He
explained that when a species speciates, it "ceases to exist,"
and is thus not a paraphyletic taxon. So, for example, when a new
species B "buds off" as a subpopulation of species A, species A
vanishes (just like that!) and is replaced by species B and a new
species, C, which holds all those descendants of A that are not
in B.

(No--I'm serious! This is how he said it!!)

Well, if the species "ceases to exist," what meaning does this
have for the clade that comprises the descendants of that no-
longer-existing species? It would seem, from the foregoing, that
the only parts of any clade that "exist" are the terminal taxa,
and that most of the clade therefore does not "exist."

Cladists seem to use the word "exist," to suit their purposes,
_very_ freely indeed.