[Taxacom] orangutan outrage

Richard Zander Richard.Zander at mobot.org
Thu Jun 25 18:26:54 CDT 2009


Rich Pyle's comments are cogent but I'd like to add another dimension.
 
Macroevolution is the transition from a node on the cladogram to a taxon represented by an exemplar. "Phylogenetically informative" only refers to information about sister-group relationships, not about macroevolution. 
 
Both creationists and phylogeneticists abhor macroevolution:  one says new species are derirved from a metaphysical god, the other says they are derived from a metaphysical node (representing an unnamed shared ancestor). Descent with modification is not directly represented in phylogenetic data sets, which are analyzed for their sister-group information. 
 
I'll bet molecular information will be really informative about ancestor-descendant (macroevolution) relationships, but it is not apparent in most published phylogenetic studies. (If morphological traits can be mapped on a molecular tree, why not taxa?) The relationships of homo, pan, gorilla, and pongo with their nodes, seems critical. Can we characterize the nodes?
 
If gorilla and pan were on a very short shared branch that did not show up in molecular cladograms, then the paraphyletic group homo-pongo would be the ancestor of gorilla-pan (mapping the traits that characterize the taxa). Any evidence for a short molecular branch connecting gorilla and pan?
 
_______________________
Richard H. Zander
Missouri Botanical Garden
PO Box 299
St. Louis, MO 63166 U.S.A.
richard.zander at mobot.org
 

________________________________

From: taxacom-bounces at mailman.nhm.ku.edu on behalf of Richard Pyle
Sent: Thu 6/25/2009 1:30 PM
To: 'John Grehan'; taxacom at mailman.nhm.ku.edu
Subject: Re: [Taxacom] orangutan outrage




John:

Is it your contention that there is phylogenetically informative information
contained within morphology that is not *somewhere* in the genome?

Or, is it merely your contention that we are not yet able to extract the
phylogenetically informative information from the genome yet, and therefore
morphology serves as a more reliable indicator in many/most circumstances?

I could be persuaded about the latter, but the former is a very tough sell.
If there is phylogenetically informative aspects of morphology that are not
*somewhere* in the genome (independent of our current ability to decipher
it), then I'm struggling to understand how that information can exist (i.e.,
if it's phylogenetically informative, then it really must be heritable).

Don't get me wrong -- I'm certainly in the camp who believe that molecular
data are often over-rated, and lead to a false sense of confidence in
results.  However, I see this not as a failure of the *concept* (i.e., that
the genome is rich with information useful for reconstructing phylogeneies),
but rather as a failure in our ability to put molecular data in its proper
context, given our current state of understanding for how to interpret it
properly.  I am confident that we will eventually (perhaps within my
lifetime) have the necessary understanding to fully extract the
phylogenetically valuable information from the Genome, at which point
morphology will be useful primarily for bridging extant organisms to fossil
organisms.

I'm also keeping an open mind to the possibilities that:
1) There may be phylogenetically useful information observable in morphology
that does not exist somewhere in the genome (though I'm struggling with
imagining a mechanism);

2) It may not be possible (ever) to extract all of the phylogenetically
useful information from the genome (hard to fathom, given that the
phylogenetically informitive morphology is almost by definition derived from
the genome, and if the biomolecules know how to extract that information,
then we should eventually be able to do so as well);

3) Human civilization may collapse before we achieve the necessary level of
understanding of the phylogenetic aspects of genomic information.

Aloha,
Rich






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