[Taxacom] Phylogenetic Game
Richard.Zander at mobot.org
Sat Dec 11 17:11:07 CST 2010
Fitzhugh is right about causality. Cladograms are parenthetically nested
sets of extant specimens, the nesting being a pattern apparently due to
shared ancestry. This is a pattern of evidence of descent with
modification of taxa, yet cladistics provides no theory of the evolution
of the groups involved. Only offered by cladistics is the pattern of
nesting of the result of evolution. We are supposed to classify all
organisms by the pattern of nesting of extant taxa due to shared
Seems okay on the face of it, doesn't it? Don't we all search for
patterns? Well, the pattern of evidence is never used by cladists to
create a theory of evolution of the groups involved. The pattern IS
evolution, and there is no theory. All mapping of trait changes,
biogeography, and so on are theorems, not theories, because all
deductions from an axiom or first principle must be correct (apodictic).
No theory, no science.
Only extant specimens are used in creating cladograms. Thus, the pattern
reflects no theory of extinct lines that may affect interpretation of
evolution. E.g. what is the chance that there is an extinct line of
polar bears below the splitting of the two molecular lines of brown
bears in the cladogram ((polarbear, brownbear1) brownbear2) . . .?
Small, because the autapomorphies of the polar bear are unique and
highly specialized. So it is probable that the polar bear evolved from
one line of brown bears. But one is not allowed to use discursive
reasoning or induction or any theorization in phylogenetics.
Phylogenetics is not science.
An evolutionary systematist, on the other hand, can use induction to
infer macroevolutionary changes and their direction, that is, one taxon
changing into another through descent with modification. Paraphyly on a
molecular tree is one indication of such a progenitor-descendant
relationship, and it can be further analyzed with reasonable application
of Dollo's rule using biogeography, cytology, chemistry, and other
directional changes to gauge the probability of taxon A evolving into
taxon B, or did it happen vice versa? But that additional information is
not as certain as the patterns of evidence comprising the cladogram, and
the "rocket science" statistical certainty of the (molecular) cladogram
would collapse if such additional evidence were to be used.
It is the self-serving saving of apparent "rocket science" that animates
cladists of both morphological and molecular stripe into enforcing the
principle of strict phylogenetic monophyly. Abandoning empiricism for
structuralism (look it up) is the bane of present systematics, and
adversely affects our stewardship of biodiversity by epistemological
extinction of taxa that render other taxa paraphyletic (if something has
no scientific name, then biodiversity stewardship is crippled). There is
also a scrambling of nomenclature and proliferation of "cryptic"
molecular variants that dilute appreciation of significant
macroevolutionary entities when perceiving patterns of evidence as
evolution itself rather than using induction to create robust and
responsible theories. Phylogenetic analysis does use powerful tools that
might prove helpful in devising an evolutionarily based classification,
but the results of their use to date is, in my opinion, a disaster.
It is time to stop pussyfooting around and begging phylogeneticists to
allow recognition of paraphyletic taxa. Paraphyly is when nomenclature
does not agree with unanalyzed patterns of evidence of macroevolution in
the theory-free context of structuralism. Phylogenetics is not science.
* * * * * * * * * * * *
Richard H. Zander
Missouri Botanical Garden, PO Box 299, St. Louis, MO 63166-0299 USA
Web sites: http://www.mobot.org/plantscience/resbot/ and
Modern Evolutionary Systematics Web site:
From: taxacom-bounces at mailman.nhm.ku.edu
[mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Simon Mayo
Sent: Saturday, December 11, 2010 1:31 PM
Subject: Re: [Taxacom] [Taxacom Digest] Phylogenetic Game
"Classification rather than systematization. Demarcating groups rather
than causal explanations." - (J. Kirk Fitzhugh)
Well...not rather than, just as well as and prior to causal
explanations. All cladograms are based on patterns surely?
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