[Taxacom] quote of the week

[John Grehan]

I acknowledge that some may argue that all things may be the same. In the case of the ear I can point to a positional homology - what appears to be an ear is postionally in the same place as another apparent ear. Anyone can go and see that. With positional sequence homology one cannot do that. One has to put one's faith in a theoretical mathematical model of how molecular evolution is believed to have worked.

John Grehan



> -----Original Message-----
> From: taxacom-bounces at mailman.nhm.ku.edu [mailto:taxacom-
> bounces at mailman.nhm.ku.edu] On Behalf Of Pierre Deleporte
> Sent: Thursday, March 20, 2008 9:45 AM
> To: taxacom at mailman.nhm.ku.edu
> Subject: Re: [Taxacom] quote of the week
> 
> 
> self-quotes of the week :
> 
> Sequences are not passing by 'pre-aligned' out there in nature;
> but neither do squeletons and anatomies.
> 
> Morphologists do have 'alignment problems';
> some mammals appear to have 12, 13, or 14 pairs of ribs...
> and snakes can show many more
> (they were likely paid by vicious molecularists for behaving such a
> tricky way).
> 
> Aligning bird and human squeletons was an enlighting biological
> conjecture,
> despite the frustrating fact that squeletons themselves obstinately
> refused to align spontaneously
> (such a lack of cooperative spirit is absolutely baffling ...).
> 
> Homologies are concepts, inferred properties,
> they are not observable material systems or processes (= changes in
> systems).
> 
> Ears exist in  nature as things protruding on living beings, not
> 'homologies';
> while homologies do not exist in themselves,
> except as sequences of thought activities in human brains.
> 
> When nobody is thinking some homology, no homology is "existing"
> properly on Earth;
> (which is not to say that the homology is erroneous when thought).
> 
> Confusing interpretative concepts with objectively 'observable' material
> objects
> or processes has one name (at least): naive positivism (pleonasm).
> 
> Pierre
> 
> 
> Hovenkamp, P. (Peter) wrote :
> > John,
> >
> > >From your opponents you require the same infallibility that you claim
> > for yourself. Both are unrealistic.
> >
> > They observe two sequences. They conjecture an alignment.
> > You observe two ears. You conjecture homology.
> >
> > Same difference.
> >
> > Peter Hovenkamp
> >
> >
> >> Subject: Re: [Taxacom] quote of the week
> >>
> >> I guess it is radical, but then it's the molecularists who have pushed
> >> the distinction (and superiority) of molecules.
> >>
> >> I can observe or define an ear homology as something that exists in
> >> nature. When alignment is involved, as it is so often, homologies are
> >> created that do not exist in nature - they are the product of one or
> >> more alignment programs. So the sequences are empirical, but the cross
> >> species homologies of sequences are not when they are the product of
> >> alignment.
> >>
> >> John Grehan
> >>
> >>
> --
> Pierre Deleporte
> Université de Rennes 1
> CNRS UMR 6552
> Station Biologique de Paimpont
> F-35380 Paimpont   FRANCE
> Téléphone : 02 99 61 81 63
> Télécopie : 02 99 61 81 88
> 
> 
> 
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