[Taxacom] more on molecules

John Grehan jgrehan at sciencebuff.org
Thu Nov 20 12:15:08 CST 2008

A while back I think a list member kindly drew my attention to Rieppel
and Kearney (2007) The poverty of taxonomic characters (Biology and
Philosophy 22: 95-113). This paper made a number of points of interest
to the morphology-molecular problem in reconstructing human origins.


Rieppel and Kearne note that alignment of multiple sequences of
different lengths face the problem of whether and/or how to insert gaps
to obtain the 'best' alignment which entail "a degree of subjectivity"
(not sure how degree comes into it - its either subjective or not?).


They point out that there an increasingly algorithmic approach to
characters has become predominant in morphological analysis under the
paradigm of a total evidence approach that lacks critical evaluation of
homology hypotheses. I see this as also particularly true of molecular
analysis, and true of much of the morphological analyses of higher
primates where all sorts of similarities have been proposed without
adequate corroboration through documented outgroup comparison 


The comparison of molecular and morphological relations of homology are
characterized by Rieppel and Kearney as problematical [understatement in
my opinion] because of the problems of alignment and shifting domains of
homology under the direct optimization alignment procedure.


Rieppel and Kearne also state that molecular systematists today focus on
maximal congruence of as many data as possibly under the assumption that
a statistically significant degree of congruence would not occur due to
chance alone. If this characterization is not a restatement of pure
phenetic reasoning I don't know what is.


John Grehan




Dr. John R. Grehan

Director of Science

Buffalo Museum of Science1020 Humboldt Parkway

Buffalo, NY 14211-1193

email: jgrehan at sciencebuff.org

Phone: (716) 896-5200 ext 372




Ghost moth research


Human evolution and the great apes




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