homology in biogeography and biology

Tom DiBenedetto tdib at UMICH.EDU
Wed Sep 22 19:02:24 CDT 1999

John Grehan wrote:

>Tom DiBenedetto wrote
>>Yeah,  homology means "the same feature found in different organisms,
>>as a result of descent from a common ancestor".

>If the concept of homology is restricted to similarity of features (or same
>found in different organisms, then by definition there is no such thing as
>homology in biogeographic distributions.

Please note: it is not simply "similarity of features" (or as Richard
Jensen wrote: "a similarity reflecting common origin"), it is
similarity of features *as a result of common ancestry*.

>If one takes a broader concept of homology to refer to the same or similar
>found in any two or more units of comparison, then homology is a concept that
>could apply to biogeography.

But this seems to leave out the notion of descent from a common
ancestor, which is at the heart of our understanding of homology, and
has been for a very long time.

>In panbiogeography any two distributions sharing
>the same geological/geomorphic feature (i.e. their tracks both cross this
>may be said to be homologous with respect to that feature.

Why hijack the word homology though? Why not simply say that they are
similar? Maybe I am missing something here, but this sounds as bad as
some of the molecular types who use "percent homology" to mean "percent
similarity". To me this is just  conceptual inflation. Homology has a
much more restrictive meaning than just similarity.

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