Doug Yanega dyanega at MONO.ICB.UFMG.BR
Tue Jun 17 13:33:32 CDT 1997

Thomas Pape wrote:

>At 11.12 1997-06-17 -0300, Doug Yanega wrote:
>>I think the present example is one which
>>offers a good reason why subjectivity DOES have a place, myself. A
>>systematist can publish the shortest tree in the results section, yet still
>>go into a discussion of why he/she doesn't believe it should be accepted at
>>face value. That seems like honest science, to me.
>Sure - but this is not a "good reason why subjectivity DOES have a place" in
>systematics. Nothing needs to be "accepted at face value", not even shortest
>trees. A random collection of data is likely to produce one shortest tree,
>but this does not mean that we would have to accept it.

??Then we don't really have a difference of opinion, it appears - a *truly*
objective analysis WOULD accept results at face value, because to do
otherwise requires *some* measure of post-hoc explanation, i.e., subjective
interpretation. If you claim we don't have to accept the shortest tree as
the best hypothesis, if we have information external to that which was used
to construct the tree (hypotheses of peripheral isolation in the present
case), then you are in fact arguing for some permissible degree of
subjectivity, which is all I was saying.

>And for this very same reason we need not base our decisions on subjectivity
>- apart, of course, from the naming of (paraphyletic) groups.

*Not needing* to make subjective interpretations, and being *allowed* to
make subjective interpretations are two different things, perhaps? I was
once criticized for lack of objectivity for suggesting that one might wish
to ignore traits like lack of eyes and pigmentation when reconstructing
phylogenies of cave-dwelling organisms (the example at the time) because we
have valid reasons to expect homoplasy in these traits in such a case. I
was told that if one ever doubts the results of one's analysis, or thinks
that one's characters might be misleading, then instead of subjective
interpretation and/or selective exclusion of characters, the only
appropriate thing to do is gather more data on more characters and do the
analysis again (presumably until the result is what you believed it should
be in the first place, which struck me as baldfacedly subjective in its own
way). My point was and is simply that there must be a happy medium between
pure objectivity and pure subjectivity, and it is in this respect (among
others) that a living, breathing systematist is superior to a computer
algorithm for constructing sound evolutionary hypotheses (and why some
systematists are better than others), because we do *not* have to accept
everything at face value, and knowledge beyond what is in one's character
matrix can be very valuable. Knowing when and when NOT to "argue" with
one's results is the real trick, obviously. That's what makes things
interesting, no?


Doug Yanega    Depto. de Biologia Geral, Instituto de Ciencias Biologicas,
Univ. Fed. de Minas Gerais, Cx.P. 486, 30.161-970 Belo Horizonte, MG   BRAZIL
phone: 031-448-1223, fax: 031-44-5481  (from U.S., prefix 011-55)
  "There are some enterprises in which a careful disorderliness
        is the true method" - Herman Melville, Moby Dick, Chap. 82

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