revolution

Tom DiBenedetto tdib at UMICH.EDU
Thu Oct 3 09:00:57 CDT 1996


On Thu, 3 Oct 1996 10:34:07 -0500 (EST), Richard Jensen wrote:

.  As one who has used
>phenetic methods, I can assure you that I used assumptions of homology in
>constructing character information for generating character matrices.

well, I'm sorry. I did not speak precisely. I meant that there is a
different conceptual basis for the notion of homology, i.e. no
concept of homology as derived similarity. The second phrase in my
sentence was meant as an explantion of the first, although I realize
it can be read as the second item in a list.

>Gee, I wasn't aware that everyone who conducted cladistic analyses used
>_exactly_ the same procedures.

Nor are there rigid criterea by which the term "cladist" can be
applied. But there certainly are clear methodological principles, and
a limited range of specific application, as opposed to the
operationalist implications which I read into your comments.

> What we
>need to keep in mind is that, while the two approaches have the same
>starting points (yes, right through the preparation of taxon by character
>data matrices for input to a preferred algorithm), they have explicitly
>different objectives.

Which is why i was somewhat surprised at your comments that my
description of cladistics could be confused with phenetics,,,i.e. it
seemed to be you who were not keeping these differences in mind when
reading what i wrote.

>On Thu, 3 Oct 1996, Tom DiBenedetto wrote:
>
>>
>> I disagree absolutely with this, There is no concept of homology in
>> phenetics, no vision of individual characters as marks of history,
>> and a reliance on measures of overall similarity. I dont know what
>> you mean that we "start at the same point",,,with organisms?
>> ok....The two approaches do not generate the same kind of data, and
>> in cladistics we do not analyze with a variety of procedures.

---------------------------------------------
Tom DiBenedetto
Fish Division
Museum of Zoology
University of Michigan




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