cladism's greatest weakness

Thomas Pape thomas.pape at NRM.SE
Fri Sep 17 19:16:16 CDT 1999

Don't mix classification with cladistic theory.

>     The continuity of evolution is such that cutting the evolutionary tree
>is going to be arbitrary to some degree no matter how you do it.

Cutting the tree is a matter of classification and beside, if not irrelevant to the concept of paraphyly. The "continuity of evolution" does not prevent us from reconstructing this very continuity. And given that we want to reconstruct evolution (and for the moment assuming that we have, or may further refine the tools to do so) Curtis' point should come through crystal clear. Reptiles have their basal branching pattern resolved and for this reason appear as paraphyletic on the cladogram with respect to birds. That is simply a matter of definition. A population 'budding off' peripheral isolates is more tricky but poses no problem to the underlying theory even if more difficult to analyse. Hybrids and reticulate evolution is another difficulty we have to face and which even may create problems for the concept (or definition) of paraphyly, but none of this violates nor even challenges the basic cladistic principles.

>Unfortunately, strict cladists have used Hennig's assumption to mask the
>fact that they are just substituting one kind of arbitrariness for another.

Huh ??

Thomas Pape

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

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