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February 10, 2005

Cladistics and evolution

Those who follow the Intelligent Design movement will no doubt be aware of the recent paper by Stephen Meyer in the Proceedings of the Biological Society of Washington. Plenty of ad hominem has been brought to the table for Sternberg, Meyer, and the Smithsonian staff. I'm not really interested in talking about that, though if you want to read about it, the relevant links can be found at Panda's Thumb (and Dr. Sternberg has his own web site if you want his side). My personal feeling is that Sternberg may just be a truly open-minded person who was more than a little naive about his (perceived) role as a gatekeeper.

I'm much more interested in Sternberg's claim that his work in systematics need not rely on evolution as an assumption. Thus, he unflinchingly advises chiefly young-earth creationist organizations on scientific issues surrounding the classification of living things. While most taxonomists would probably not be so ecumenical, methodological evolution-agnosticism is nevertheless a mainstream view in cladistics. How can taxonomy be assured of its correctness if it is divorced from evolution, you might ask? I did, too. It seems the whole argument hinges on a philosophical identity crisis: the ontological basis of systematics.


Consider this paper in Cladistics. In it, A. V. Z. Brower writes that "the assumption of evolution in process cladistics is a methodological plesiomorphy ... that no longer contributes to the discovery of heirarchical patterns of taxonomic grouping. Nowhere in the procedures ... which are those used by cladists of every stripe today, is an evolutionary assumption required in general or particular." The author agrees that macroevolution is true; neverthe less, "the theory of macroevolution is corroborated by evidence from systematics ... therefore, the a priori assumption of descent with modification fails to provide independent ontological support for systematics." Assuming that a certain evolutionary history is correct as currently known could taint a proper systematic study.

So it would seem that the approach taken by cladists keeps them from going astray. But does cladistics claim for itself an explanatory role? Because if it does, cladists must have a very hard time arguing that any particular evolutionary history is wrong based on systematics alone (their homology being typology, character, Platonic kind, or...?). I'm left scratching my head over the inscrutibility of it all.

Posted by The Greatness at February 10, 2005 12:06 PM

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