Continuity, reticulation, and classification

Thomas DiBenedetto tdibenedetto at OCEANCONSERVANCY.ORG
Wed Jul 25 12:09:43 CDT 2001

-----Original Message-----
From: Ken Kinman [mailto:kinman at HOTMAIL.COM]
Any bioclassification is a construct and arbitrary. The tree of life is a
continuity, and any cuts to divide it into taxa are arbitrary.  Cladistic
classification is just as arbitrary in a different way, and many cladists
believe that sister groups actually exist (which I find very troubling)
The notion that a classification scheme is a human construct seems to me to
be rather obvious. I note that Ken then links the word "arbitrary" to
"construct" almost as if it were a necessary qualifier. Or at least he has
not endeavored to make a real argument for why a cladistic classification,
admittedly a construct, cannot also be non-arbitrary. I believe that it is.
My dictionary defines arbitrary as "depending on individual discretion" or
"based on or determined by individual preference or convenience rather than
by necessity". There seems to me to be no question that an eclectic
clssification is arbitrary - I guess Ken doesn't dispute that point. But
cladistic classifications are not arbitrary - one simply cannot inject
personal preferences into the process of going from a data matrix to a
classification scheme. It is a rule-bound step - the most parsimonious tree
that is discovered by the algorithm automatically becomes the
classification. One cannot modify it in any way, irrespective of ones
personal preferences, hunches, gestalts, evolutionary models etc.
If one were to claim that all human intellectual products (constructs) are
arbitrary, then the term becomes meaningless. The term is meant to
distinguish those actions or concpets that are not yielded by a logical rule
from those that are. There may be many steps in a systematic enterprise that
one might argue are arbitrary, but the production of a cladistic
classification from a data set is not one of them.
In addition, I strongly disagree with the notion that "any cuts to divide it
[the continuous tree of life] into taxa are arbitrary". Fundamental to the
entire enterprise of taxonomy and systematics is the perception that life is
segragated into independently evolving, discrete and distinguishable groups.
One might claim that the decision that humans have made to study the
diversity of life was an arbitrary decision (as opposed to deciding not to
study life). But once the decision was made, I think that the subsequent
cladistic decision to name and identify lineages by their distinctivness and
historical segregation from the rest of the tree follows as logically (and
non-arbitrarily) as the decision of taxonomists to recognize species by
their distinctiveness and segregation from the rest of life. Cladistics is
really nothing more than the taxonomy of groups of species. Cladists simply
do not arbitrarily modify their empirical findings to produce
classifications that are judged to be more useful or less up-setting than
the findings themselves.

Tom DiBenedetto

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