[Taxacom] quote of the week
murrellze at appstate.edu
Thu Mar 20 11:17:18 CDT 2008
Below are a few issues that have been difficult for me. Any
clarification would be helpful.
Is a homology a concept or a hypothesis?
If we polarize two characters states (using outgroup analysis), is that
polarization a hypothesis?
Is the phylogenetic tree derived in a parsimony analysis a hypothesis, a
model, or a concept?
Pierre Deleporte wrote:
> 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
> Ears exist in nature as things protruding on living beings, not
> 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
> or processes has one name (at least): naive positivism (pleonasm).
> Hovenkamp, P. (Peter) wrote :
>> >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
>>> John Grehan
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