Weights

Tom DiBenedetto tdib at UMICH.EDU
Fri Mar 7 21:11:05 CST 1997


On Fri, 7 Mar 1997 15:39:59 -0800 (PST), James Francis Lyons-Weiler
wrote:

>Tom DiBenedetto wrote:
>
>>the inference would be different than the historical reality.  You
>seem to equate "failure" with arriving at results that differ from
>the expectations of generaliztions drawn from different and
>independant circumstances.
>
>       Sorry for being blunt, but this response seems hackneyed; you
>       elsewhere offer a justification of cladistics based on first
>       principles of evolution; certainly Hennig
>       justified cladistics as following naturally
>       from an understanding of Darwinian (selectionist)
>       thinking.  Perhaps these points about generalizations
>       are ubiquitous (it does take a leap of inference
>       to take a tree as an estimate of phylogeny.

Strikes me that there is a big difference between developing methods
structured around deductions from higher-level theories (what you
assert Hennig and I did), and structuring tests which are made
sensitive to inductive generalizations from previous tests (what I
accuse y'all of doing).
As to the phylogeny point,,,let me make this (possibly nit-picky)
response,,,,(one never knows what might set the light-bulbs off)...:
Although I understand the inferential leap that those of you who
"estimate" phylogeny are making,,for us I think it is somewhat
different. The analogous leap which we make is not so much from tree
-> phylogeny, but rather from character -> homology. Each
corroborated homology sitting in a matrix awaiting 'final"
corroboration in the congruence test, is already a little
phylogenetic hypothesis; the leap has already been made. The logical
combination of homologies is also a logical combination of
phylogenetic hypotheses, such that when one arrives at a tree, all
the leaping has already been done.




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