cladism's greatest weakness

Thomas Pape thomas.pape at NRM.SE
Fri Sep 17 20:44:59 CDT 1999

Reply to Zander:

>Choosing the optimal one against all alternatives is arbitrary.

Taken verbatim it sounds very non-arbitrary to me! We're getting back to the old discussion of parsimony. A parsimonically suboptimal alternative simply remains suboptimal, even if differences in optimality to the closest alternatives may be so small as to be considered insignificant. Yet how to choose levels of significance  is a truly arbitrary matter.

>Bremer support of say 10 on a branch that is 40 steps long leaves 30 steps
>of data supporting an alternative, and I think reasonably supported branch.

You cannot argue for 'reasonable support' out of context. First, a Bremer support of 10 means that ANY alternative not carrying the branch in question will be at least 10 steps less parsimonious. Second, "30 steps of data" is not necessarily 30 steps of support. Third, any "reasonably supported" branch would be discarded in favour of any such branch with a (reasobably) higher support.


Thomas Pape
Department of Entomology
Swedish Museum of Natural History
Box 50007
SE - 104 05 Stockholm
   thomas.pape at

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