Human and ape phylogeny

David Williams dmw at NHM.AC.UK
Tue Apr 8 09:58:44 CDT 2003

Dear Peter,

First point, yes it was a slip of the pen, I meant vertebrae -- email
preserves the haste in which they are written. The fact that homologous
structures may be found non-vertebrates says nothing of vertebrates (that
was Rene's point, 'paraphyletic characters' = plesiomorphies). One might
consider the basis for comparison, say at the cellular level, then what?

You missed the point of my second example. Yes it did make sense to Owen
and many others, after all much 'homologising' was done during that period
(theories which still stand the test of time). You seem to have indulged in
judging Owen and his contemporaries by our standards, which is the wrong
way to do it -- and which why I used the example. Surely you meant to write
"Owen's derivation of vertebrate parts does not make sense in an
evolutionary world", or did you? In any case, Rene states quite precisely
and clearly "Perhaps you think that characters are observable bits of
truth, but characters are ideas (hypothesis, theories), not observations."


>The first point is based on a misunderstanding - understandably, perhaps,
>because I just gave a short reply, not a longish treatise on homology. To
>answer it I would recall that vertebrae (if that's what were talking about,
>otherwise I give up) did not develop from scratch - iirc there are
>homologous structures in non-vertebrate chordates.
>Second point is more interesting, as it is in fact true. Owen's derivation
>of vertebrate parts does not make sense in a non-evolutionary world. It is
>one of the "explananda" of which evolution is the "explanans".
>Peter Hovenkamp

David M. Williams
Department of Botany
The Natural History Museum
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London SW7 5BD

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