|
A Manifesto for Evolutionary
Systematics Richard H. Zander December 23, 2010 |
|
A Manifesto for Evolutionary Systematics Richard H.
Zander, This is a call
for serious reappraisal of modern systematics. Do you remember when there was
a “paradigm change” some decades ago, and we taxonomists were supposed to
reject theories as just-so stories, redefine evolution as relationships on a
cladogram, reframe evolution as changes in traits not taxa, abandon
scientific induction in favor of hypothetico-deductivism,
and revile as mere “intuition” the results of 250 years of taxonomic
expertise and discursive reasoning? It is time to consider a total rejection
of structuralism hiding in plain sight in systematics. Phylogenetic
analysis extracts from homologous character data sets patterns of
evolutionary relationships, just as all basic evolutionary evidence is based
on similarity. The software-generated patterns are, however, neither
hypotheses nor theories because they do not directly detail possible causal
relationships of natural processes that can be investigated and falsified, or
supported by additional facts. These patterns are evidence of
processes involved in the natural generation of species and higher taxa for a
particular group. Interesting and helpful evidence, but only evidence. Phylogenetics
is not science. Phylogenetics rejects forming theories using evidence and
induction. Instead it treats patterns of evidence of macroevolution as the
phenomenon of evolution itself, and uses deduction alone to form what are
essentially apodictic theorems, avoiding theories of process in nature.
Following Thomas Aquinas, when one has the correct first principles, all
deductions must be correct. This is
structuralism, a “content-free” methodology
common in linguistics, anthropology,
psychology, and other areas, intended
to replace empiricism. Structuralism attempts to introduce an element of
“hard science” into non-mathematical and non-physics-based fields. This is
done by identifying basic patterns that may be taken as axiomatic or
irreducible first principles. In phylogenetics, the structure of the
dichotomous tree is “saved” by rejecting all theory-based ancestor-descendant
relationships in favor of a forced sister group parenthetical nesting of
exemplars. Internal consistency of the method is aided by administrative
enforcement of the principle of holophyly (strict phylogenetic monophyly).
The statistical certainty or near-certainty of patterns of nested exemplars
in molecular systematics is “saved” by ending analysis at the level of the
nested exemplars, rejecting induction of process-based theories of
ancestor-descendant relationships from those evidential patterns and from
other data. Phylogenetic “testing of
hypotheses” is simply comparing patterns of evidence. Even if morphologically
and molecularly derived patterns are “consilient,”
they are themselves not hypotheses but are only patterns of evidence. If such
patterns differ, there is actually information in that difference because the
patterns are not theories, that is, there is no comparing of alternative
processes. The differences, in fact, may be used to generate process-based
theories. Phylogenetic analytic methods of clustering are innocent and can be
powerful, but the interpretation of the results (as pattern equals evolution
and classification must follow such patterns) is not just flawed but is
non-science. Structuralist thinking necessarily
eliminates any reflection of macroevolution in classification. The “tree” of
life has no scientific realism or theoretic substance because nodes are not diagnosably named, and the dendrogram
is just a visual aid for often complex evidential patterns of nested
exemplars, just as is the case in ultrametric
cluster analysis. Scientific empiricism rejects solutions involving unnamed
or unobservable entities or hidden causes. The introduction of other, less
certain data or theories (e.g., from morphometrics,
fossils, cytology, biogeography, chemistry, development) as additional
evidence for scientific induction of evolutionary process involving descent
with modification of taxa would collapse the pattern-based statistical
certainty of molecular cladograms. Thus, in cladistics,
all data outside the data set that are relevant to
macroevolutionary theory are “mapped” on the dendrogram
or in some other way relegated to the fundamental structure of the cladogram.
This is not science. Important taxa in conservation
and biodiversity research are being synonymized as a kind of epistemological
extinction. Their identity is often intellectually scrambled by transfer into
disparate and heterogenous groups, or to those that
are molecularly diagnosed, or they are buried among molecular cryptic
species, genera and families. It is understood that phylogenetics is
presently fueled by comparatively high levels of funding, distinction of
association with DNA studies, highly sophisticated mathematics supporting
apparent statistical certainty of patterns in many cases, and ease of
generating results as was the case with the “automatic taxonomy” of phenetics. But without names or sensible nomenclatural
handles for macroevolutionarily significant taxa,
stewards of biodiversity are stymied. An immediate return is
urged to the practice of evolutionary systematics and process-based science.
This involves using all evidence, including both sister-group and
ancestor-descendant analysis, the importance of both similarity and difference,
and use of both induction and deduction to form theories of evolution of
natural groups upon which a robust and responsible classification can be
based. Pluralistic taxonomy is not easy and its results are not certain but
it is scientific. It is a challenge that can be aided by modern methods of
non-ultrametric cluster analysis but never in the
context of structuralism. This Manifesto is mainly
targeted towards students, because established phylogeneticists used to
“tree-thinking” have difficulty thinking outside that structuralist box, and also towards
unaligned alpha taxonomists who should be aware of the non-empirical
structuralist basis behind recent massive changes in classification. To be as
short and clear as possible, documentation was eliminated from the above.
Readers may find additional discussion, examples of taxonomy papers using
modern evolutionary systematics, and references to the works of authors with
similar or at least relevant observations on the Modern Evolutionary
Systematics Web page: http://www.mobot.org/plantscience/resbot/EvSy/Intro.htm |
|
|