cladism's greatest weakness

Curtis Clark jcclark at CSUPOMONA.EDU
Fri Sep 17 07:24:33 CDT 1999

At 11:10 AM 9/17/99 +0200, PIETER WINTER wrote:
>The "different nature" of paraphyly at different levels is presented as
>sort of obvious truth. I must have missed something. Can anyone elaborate
>this? Surely they are both the results of the same process, separated only

>by time and extinction long after the event?

If one accepts speciation as an evolutionary process, then a single
speciation event separates a progenitor from its peripheral isolate. In the
case of the Reptilia vs. Aves, a multitude of separate speciation events
separate the first reptile from the first bird. People have to choose
*which* speciation event (or in actuality the large and until recently
virtually unknown ballpark that encompasses that speciation even) separates
reptiles from birds. It is no longer an observation and interpretation of
natural processes; it becomes a debate over "birdness".

Curtis Clark        
Biological Sciences Department             Voice: (909) 869-4062
California State Polytechnic University      FAX: (909) 869-4078
Pomona CA 91768-4032  USA                  jcclark at

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