Regulatory cascades (was: Orangutan-human clade)
kinman at HOTMAIL.COM
Wed Apr 9 16:54:47 CDT 2003
"If one chooses to be skeptical... one is free to do so." ???? Your
enthusiasm is rather "underwhelming". ;-) I think it would be foolish for
me NOT to be skeptical. TBox and other regulatory genes can cause a whole
cascade of structural (and even behavioral) character transformations.
I detected a definite pattern in the character suite you presented,
and if most of those transformations COULD be traced back to a single
mutation in a regulatory gene, you are going to be just spinning your wheels
no matter what kind of analysis you use.
Genetic diseases (especially those which involve regulatory genes) and
the pattern of organ systems they effect are a largely untapped resource
which we can't afford to ignore (especially in vertebrate evolution and its
phylogeny). Even paleontologists should be paying attention to such
patterns in the lists of synapomorphies they analyze (although my attempts
to point this out to some dinosaur workers have been dismissed with silly
arguments that they have a "bigger list of synapomorphies" than I do).
So yes, I am invoking this possibility for other phylogenies where I
discern a pattern. It is a very disturbing thought that a single base
change in a regulatory gene could be equivalent to dozens or even hundreds
of disparate morphological characters, but we cannot afford to ignore it
(especially when an interesting pattern jumps out at you). My view is that
there isn't nearly enough skepticism in evaluating cladistic analyses, thus
diluting the much greater potential that cladistics has an analytical tool.
Whether the orangutan-human data set suffers from the above-mentioned
problem remains to be seen, but I hope I am scaring you enough to take it
>From: John Grehan <jgrehan at SCIENCEBUFF.ORG>
>Reply-To: John Grehan <jgrehan at SCIENCEBUFF.ORG>
>To: TAXACOM at USOBI.ORG
>Subject: Re: Orangutan-human clade (brainstorming a little)
>Date: Wed, 9 Apr 2003 08:16:57 -0400
>At 03:34 AM 4/9/2003 +0000, Ken Kinman wrote:
>> Thanks for posting that list of putative synapomorphies of the
>>putative human-orangutan clade. It was rather impressive at first, but I
>>quickly became more skeptical.
>> These characters tend to cluster in areas like the shoulder, lower
>>head (incl. teeth), and urogenital system.
>If one chooses to be skeptical about characters because they are clustered
>in a particular body 'area' then one is free to do so.
>>Unfortunately, a single base mutation in a TBox gene can cause changes in
>>these same disparate body regions (e.g., Pallister's
>>Syndrome). Therefore, the possibility that some mutation or two could
>>likewise have caused convergence (homoplasy) between humans and orangutans
>>must be raised.
>One could invoke the same possibility for the other phylogenies.
>> I don't have the time to explore this possibility more deeply right
>>now, but perhaps it is something you might want to consider. I can only
>>speculate whether this could be a rather complex "peanut butter sandwich"
>>phenomenon, but I certainly wouldn't rule it out.
>So could the other phylogenies.
>Thanks for the feedback.
>Dr. John Grehan
>Director of Science and Collections
>Buffalo Museum of Science
>1020 Humboldt Parkway
>Buffalo, New York 14211-1293
>Voice 716-896-5200 x372
>jgrehan at sciencebuff.org
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