Turning around

[Richard.Zander at MOBOT.ORG]

The whole point of molecular systematics is that it is hoped that
differences in DNA usually or mostly do NOT reflect evolution directly,
because if they did, we would have the same problem with convergence as is
the case with morphology and molecular analysis would then not be a second,
independent test. Molecular traits are, it is hoped, not connected to
anything in morphology. They just accumulate with each event of speciation,
and the ones shared the most are the most ancestral. The logic is great, the
execution so far problematic, possibly because of the inclusion of many
apparently noncoding or codon-synonymous sequences that are actually subject
to selection pressures.

Regarding orang-homo morphological similarity in the face of contradictory
molecular data that statistically well-supports pan-homo as terminal in the
clade, my suggestion of a theoretically understandable violation of Dollo's
law by long silenced and recently reactivated gene clusters does not falsify
anything. Molecular analysis does seem to show orangutan left in the
evolutionary dust, yet morphology does seem to show a set of ancient
orangutan genes reactivated in homo in selective response to particular
environmental conditions. As an explanation, it works, but proof is so far
lacking.

It is a waste of time to worry which is the "true" evolution:  the
phylogenetic tree that infers nested sets of genetic isolation events,
presumably with associated fixation of incrementally established new traits,
OR the (theoretical) jump of a highly preadaptive gene complex from
orangutan to homo. If you decide that the latter is a better theory or the
only theory, you need to be able to defend it well in the marketplace of
ideas. In my case, I think both processes occur, and much that is
problematic about our understanding of phylogeny may not be soluble with
current methods.

______________________
Richard H. Zander
Bryology Group, Missouri Botanical Garden
PO Box 299, St. Louis, MO 63166-0299 USA
richard.zander at mobot.org <mailto:richard.zander at mobot.org>
Voice: 314-577-5180;  Fax: 314-577-0828
Websites
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<http://www.mobot.org/plantscience/bfna/bfnamenu.htm>
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<http://www.mobot.org/plantscience/resbot/index.htm>
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  _____

From: John Grehan [mailto:jgrehan at sciencebuff.org]
Sent: Tuesday, February 21, 2006 2:35 PM
To: Richard Zander; TAXACOM at LISTSERV.NHM.KU.EDU
Subject: RE: [TAXACOM] Turning around



I don't always keep track of all postings on TAXACOM. As for alternative
explanation (or at least possible explanation) - I've made them on TAXACOM
already. My principal thinking is that linear patterns of DNA sequence
similarities comprise both primitive and derived states that cannot be
identified without knowing what they are connected to in morphology. So
simply reading of linear sequence patterns is just measuring overall
similarity - whether or not it is rooted.



Regarding the orangutan-homo similarities being explained in terms of
violation of Dollo's law - am I correct this is being invoked to 'explain'
why the morphology is wrong and sequences right - or is the point something
else? Got a bit lost on that.



John Grehan