Molecular taxonomy: on way out?
Thu Jul 21 17:31:26 CDT 2005
Response to John Grehan:
>> While it has been apparent for about forty years that comparative DNA
>> studies would ultimately provide conclusive evidence for understanding
>> phylogeny, ....
>Apparent? I would say claimed.
I thought it obvious that comparisons of organisms' COMPLETE summaries
of themselves would offer the best evidence we are likely to get, and
are potentially far more reliable than the relatively crude indications
torn from them via comparative morphology, etc. I still think so,
especially now that DNA sequencing and comparisons are automated and
rather easy to perform. It has all taken longer than one might have
expected, but even the fascinating complications of repeated DNA,
overlapping genes, inversions, etc. strike me as minor problems, compared
with the uncertainties involved in arbitrarily choosing which aspects of
phenotypic variation to pursue, and defining appropriate characters and
character states ... The latter approach has served very well, of
course: it led to the 'discovery' of evolution, and it continues to
provide insights into the details. In fact, it could have achieved a
good deal more, had 20th century taxonomists expended less time on
flights of phylogenetic fantasy, and concentrated on the more laborious
and technically demanding (but ultimately far more rewarding) tasks of
pursuing variation and organizing comparative data; and it will need to
continue, if 'revealed phylogenies' are to remain in contact with the
raisons d'etre for taxonomic classification (i.e., identification and
>I take the view that even with adequate taxonomic coverage the current
>systematic approaches to DNA sequences will not preclude DNA trees
>from being phenetic as the cladistic approaches are only mimics.
You may well be right, especially re "the current systematic
approaches"; but total DNA extracts contain ALL the available
information for extant organisms, in relatively accessible form.
> ...... Science and nature articles ...... are truly dreadful .....
>when it comes to hominid taxonomy (I classify most of these hominid
>articles as pseudoscience).
I haven't been there for a long time; but to a botanist watching from
the sidelines, the Nature referees/editor seemed exasperatingly less
critical in that area than elsewhere, long before DNA was brought to
bear. For example, while they seemed to reject out of hand anything
else with a whiff of 'taxonomy' about it, they were forever publishing
descriptions of 'new' hominid taxa, without requiring the authors even
to state (let alone demonstrate) that their bits of bones fell outside
the range of variation found in living humans. Perhaps not much has
Dr. Les Watson
10, Maitland Avenue
Little Grove, Albany, Email: leswatson at westnet.com.au
WA 6330, Australia Phone: +61 (8) 98 44 4398
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