[Taxacom] Robust argument

John Grehan jgrehan at sciencebuff.org
Sun Jun 28 08:23:40 CDT 2009


I don't think there should be any trepidation over expressing any point
of view on TAXACOM. I inserted some comments below which Bob also covers
at the end. I agree with the questions Bob has raised about the
assumptions and interrelationships of evidence. 

I believe these issues over morphology and molecules have largely put
away in the closet when it comes to the assertion of molecular theory as
the be all and end all of evolutionary relationships. One sees this in
the way the orangutan sistergroup theory has been dismissed as
"preposterous nonsense" and "loopy"(behind a veil of anonymity of
course)even though the relationship is based on a fairly standard
cladistic analysis and for the most part very well documented and
corroborated apomorphies. Of course someone could come along and
demonstrate either that these apomorphies for the most part do not
exist, that our data was wrong, or that they will demonstrate that
humans and chimpanzees do indeed (and despite the failure to show this
so far) share far more apomorphic features than humans and orangutans.
But as long as the orangutan evidence gets ignored there will be no
resolution either way.

Its been interesting for me, a relative bystander at the beginning, to
see how often ignoring the orangutan theory was justified by everyone
ignoring the theory. Perhaps this is another principle of science that
should be taught to students: Grehan's first theorem of science -
Ignoring a theory is justified by everyone ignoring it.

Sorry, I apparently lack a sense of humour.

John Grehan

> bounces at mailman.nhm.ku.edu] On Behalf Of Bob Mesibov
> (1) Because the genome is passed on from generation to generation, it
> contains information we need to infer evolutionary history.

Perhaps so, but what is the 'information'? A widespread assumption is
that sequence counting of one form or another represents that
'information'. Others have pointed out that the genome is not the only
thing passed on from generation to generation. 

> (2) It is possible to infer evolutionary history using information in
> genome.

How do we know that? And again in what form does that information take?

> (3) Morphology also contains information of use for inferring
> history.

But is morphology separate from the genome?

> (4) It is possible to infer evolutionary history using information
> morphology.

If (3) is true

> (5) Literally speaking, morphology is not inherited, so morphological
> information is second-hand data derived from a heritable source: the
> genome.

Not by itself perhaps, but if morphology is consistently reconstructed
generation to generation then the process is inherited and there is
nothing 'second hand' about it. It would seem to be just as much a part
of the genome as the DNA molecules. 

> (6) No other kind of information can be used to infer evolutionary
> history, because no other information is inherited.

Geography as some have mentioned. And geographic information has
occasionally been used to predict phylogeny.

> (4) has been the basis for evolutionary inference for a long time, (2)
> a shorter time. Many people believe that (2) is better than (4)
because of
> (5), and because there is more (1) information than (3) information.
> The logic here needs defending. Why should (5) make (4) any less
> than (2)? (I think this is one of Richard Zander's points.) How do you
> compare the reliability or resolution of (2) vs (4), given that we
have no
> time machine and no other information (see (6)) that can independently
> used to infer past events? How do you know that there is more
> information from (1) of use for historical inference than from (3)?
> I think these 3 questions go to methodological assumptions. Should
> assumptions be taken as givens, equally reliable from group to group?
> worries me that posters have written THEORETICALLY in caps without
> spelling out their thinking.
> I also point to (6), which is nonsense, and comes from thinking about
> organisms divorced from their geographical location and their
> associations (think of parasitism, insect/host plant interactions,
> (6) should not be confused with (7), which might read "It is possible
> infer evolutionary history from biogeography and ecological
> That history might be blurrier than (2) and (4) histories, but how do
> total evidence enthusiasts justify their insistence on using (1) and
> evidence to the exclusion of (6) evidence? (Or is it just that *some*
> evolutionary historians can't be bothered studying all the
> complicated, ungeneralisable facts of what used to be called natural
> history?)
> --
> Dr Robert Mesibov
> Honorary Research Associate
> Queen Victoria Museum and Art Gallery, and
> School of Zoology, University of Tasmania
> Home contact: PO Box 101, Penguin, Tasmania, Australia 7316
> (03) 64371195; 61 3 64371195
> Website: http://www.qvmag.tas.gov.au/mesibov.html
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