[Taxacom] New synapomorphy for humans and orangutans

Richard Zander Richard.Zander at mobot.org
Mon Jan 4 09:04:46 CST 2010


Genome changes can't back up much unless, in my opinion, they demonstrate considerable distance between where a taxon is now placed and where it ought to go. Like, opps, wrong family. This is because of extinction. If there is x% paraphyly in a present-day set of exemplars, then there should be x% at every node to take into account ancient paraphyly that is now absent. Which significantly reduces bootstrap and credible values.
 
The above requires one to accept that one taxon may exist in two or more molecular lineages. This phenomenon is demonstrated in nearly every study that has two or more exemplars of the same taxon, yet is cognitively dissonated.
 
The orangutan problem is Taxacom's very own instructive puzzle, with equivocal signs of what the ancestor of man might be like in expressed traits. Suppose both chimp and gorilla were extinct and unknown from fossils. Well, the shared ancestor would be taken to be some intermediate between orang and man. What if there were a dozen chimp and gorilla-like lineages between man and orangutan? Well, the immediate ancestor would be something like a chimp or gorilla. 
 
I note that John Grehan has fallen into the "evolutionary relationships = evolution" fallacy. This is easy to do because of peer pressure. Relationships are okay, but indirect. We really want to know what the sequential evolutionary derivation of taxa might be, which is direct. I think we can infer the latter in many cases, e.g. when a number of exemplars of the same species bunch together on a cladogram, well the ancestral taxon is that species. Yet those who insist that relationships are the end-all of evolutionary analysis will not follow the several clear lines of investigation that follow this observation, e.g. the ancestral taxon of an autophyletic taxon is the paraphyletic taxon generating it.
 
_______________________
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 Kenneth Kinman
Sent: Sat 1/2/2010 8:11 PM
To: taxacom at mailman.nhm.ku.edu
Subject: [Taxacom] New synapomorphy for humans and orangutans



Oh dear,
      It's deja vu all over again.  But now all you need to do is to
find a genome change which backs it up (or any of your other proposed
synapomorphies).  Otherwise, it's most likely just what the authors
suggested it is---homoplastic, not synapomorphic.                     
                 -----Ken                          
P.S.  It would be interesting to know if bonobo chimps have a later
eruption of molars than regular chimps.  Wouldn't be at all surprised if
bonobos erupt closer to 4.6 years than regular chimps at 4.0 years.
With so little sampling, I wouldn't read too much into this character
anyway.  Declaring it a synapomorphy is at best premature.


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