[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Final post!!!



Jaime and others,
Michael Benton certainly believes birds are descendants of dinosaurs (non-avian), as do I, but as we have discussed, this is not same thing as saying they ARE dinosaurs.
The view that cladists are just "clarifying" what constitutes "Dinosauria" by including birds is not correct in a broader historical context. Before the cladists came along, biologists strove to find monophyletic groups in the old sense of the word (holophyletic and paraphyletic). What mattered was that a group have a common ancestor, and it was acceptable to create paraphyletic groups.
Darwin not only said that natural groups should have a common ancestor, but in his own words (in eloquent 19th Century prose) said that if modification in sister lineages occurred at greatly different rates that the more modified lineage should be given a higher taxonomic rank. Cladists flatly ignore this when they quote Darwin.
Therefore to say that these 19th Century naturalists thought that Dinosauria had to include all of the descendants of the common ancestor is reading something into it that simply isn't there.
Dinosauria and Aves were classified separately for well over a century, even by those who thought birds were probably dinosaur descendants. Even Michael Benton in his recent Vertebrate Paleontology book classifies them in separate taxa, although he did put a cross-referencing marker (functionally similar to those I use) to show that birds are descendants of dinosaurs.
--------Ken Kinman
P.S. If you want, I can try to finds one of Darwin's two passages which shows that he believes when sister groups evolve at greatly differing rates that the faster evolving group should be ranked higher in the taxonomic hierarchy. And I wasn't going to mention this, but your comments show that it needs to be brought up. Cladists not only commandeered the taxon Dinosauria (however they might try to justify broadening its scope), but they also greatly changed the meaning of the term monophyletic, from "holophyletic or paraphyletic" to holophyletic only. In fact it was this move that prompted Peter Ashlock to proposed the term holophyletic in order to clarify the situation. But the cladists would have none of it, no matter how much confusion resulted. The ends supposedly would justify the means, but unfortunately 30 years later it still hasn't ended the way they thought it would. We are still no closer to the stability they thought would result from cladistic classification methods, and in some ways it has made matters worse. Predictions that cladistic stability is just around the corner just don't wash any more.
I have no more time for trying to explain all this. I'm tired of spinning my wheels and have other things to do, so this will be the last time I spend this much effort on such threads within this newsgroup. There are obviously great philosophical differences between cladists and eclecticists, and if I haven't made any headway here to convince you that middle ground approaches are possible (and preferable) then I guess I'm wasting your time as well as mine.
-------Ken Kinman
_____________________________________________________________________________________
Get more from the Web. FREE MSN Explorer download : http://explorer.msn.com