[Taxacom] ad hoc manipulation
kinman at hotmail.com
Wed Sep 5 11:15:39 CDT 2007
The mtDNA sequences are apparently plesiomorphically similar in
prototherians and metatherians, and then there was a spurt of molecular
change in the stem-lineage leading to crown eutherians. The IGF2R sequences
apparently had a spurt both before AND after metatherians split off.
Different sequences punctuate their equilibria (so to speak) at different
times and at different rates. Differentiating between symplesiomorphies and
synapomorphies is good science, not "ad hoc manipulation" in the bad sense
that you imply.
As for your paper, perhaps the editor is rightly concerned that you
still have no molecular evidence AT ALL to corroborate your morphological
analysis. Besides, your selective lists of morphological characters have
already been published elsewhere, so even if you have add a few new ones, it
is bascially just rehashing the same arguments once again. If you could
find even a few molecular characters to support your viewpoint, then that
would actually be newsworthy.
P.S. I still strongly suspect most of your morphological characters are
developmentally connected and therefore non-independent. And if a human
clade split off between orangutans and a gorilla-chimp clade, then some of
them might be symplesiomorphies (not synapomorphies) which were then lost in
a gorilla-chimp clade. Either way, your failure to find ANY molecular
evidence to support your phylogeny is what continues to trouble me most of
>From: "John Grehan" <jgrehan at sciencebuff.org>
>To: "TAXACOM" <taxacom at mailman.nhm.ku.edu>
>Subject: [Taxacom] ad hoc manipulation
>Date: Wed, 5 Sep 2007 08:39:59 -0400
>I was interested to recently read that mtDNA analysis in 1997 had put
>monotremes with marsupials, but because that was such an abbearation
>some other molecular systematists decided to try nuclear IGF2R sequences
>and got placentals and marsupials to the exclusion of monotremes so
>everyone was happy. I am interested to know of any similar examples as
>it shows how morphology, when so contradictory to molecular results, can
>and does result in re-analysis of molecular evidence to get the "right"
>answer. This is pertinent to my interests since the human-chimpanzee
>relationship is very strongly contradicted by morphology, but no one (to
>all intents and purposes) is willing to accept the possibility that the
>molecular evidence is wrong in this case.
>For over three months I have had an article in review that has a
>cladistic analysis of the morphological evidence showing that the
>orangutan-human relationship is the best supported model. The editor was
>not at all happy to see the molecular evidence being challenged and said
>he would ensure a fair review.
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