2000 years of stasis

Thomas DiBenedetto TDibenedetto at DCCMC.ORG
Sun Feb 6 14:14:34 CST 2000

Thomas Lammers wrote:
 the fact remains that molecular data for use in systematics
are 99.9% analyzed in some cladistic fashion.
Gee, that would be nice. It seems to me that most molecular analyses are
being done by evolutioanry modelers, many of whom seem not to understand
that cladistic analysis is something different than a simplistic model of
evolutionary process.
Molecular data are ideally
suited for cladistic analysis (as compared to, say, quantitative morph
features) due to the large number of characters, and the paucity and
distinctness of the states.
I think molecular data are certainly amenable to cladistic analysis, but are
hardly ideal. The paucity of states, especially the fact that one state is
necessarily overwritten by an evolutionary change, and thus irretrievable,
is a huge disadvantage. But that speaks to the weakness of molecular
characters for systematics in general, not just cladistics.
For better or worse, molecular biology could
not have made the inroads and the contributions (a double-edged sword if
ever there was one) that it has made to biological systematics  without
I basically agree. Whatever knowledge we have gained about phylogeny from
molecular sequences has come from cladistic analyses.
My complaint is with those who get SO hung up on getting the patterns to fit
their preconceived notions of how evolution ought to work, that they are
blinded by how evolution DOES work.  We are so fixated on "homoplasy is
bad" that we blind ourselves to times when evolution may not in fact have
been parsimonious.
Sorry, but I dont understand your point here at all. What preconceived
notions about evolution are you talking about? You sound like those modelers
who dont understand cladistics. Parsimony is NOT a model of how evolution
works! Cladistics is NOT dependent on an assumption that evolution is
parsimonious (whatever that might mean). Parsimony is merely a logical
criterion for choosing one of several hypotheses, and the choice is made on
the basis of which hypothesis is supported by the most evidence. It may or
may not be true, but as rational people, we have an obligation to respect
the evidence.
Read the cladistic literature, study it thoroughly; then read the
literature of evolution processes, speciation, population biology.  You
would never suspect they were describing the same phenomena.
Having done both, I would agree that there is often a disconnect. But I have
also noticed that most cladists I know are reasonably well-read in these
related fields (since most of us were trained in one of those fields before
learning about cladistics). But precious few non-systematists, and
suprisingly, many systematists, seem not to have learned very much about
cladistics; many of the critiques I read seem to come out of left field.
Your statement seems to imply that if there is a disconnect, the fault must
lay with cladistics. I would suggest that, at the very least, you should
encourage both sides to broaden thier horizons.

Tom DiBenedetto
tdib at dccmc.org

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