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Re: Clade II (long)



Last one on cladisitcs until I read the paper, I promise...

> Yes, it does: it forms a group composed of common ancestors and all its
> descendants (or a common DNA heritage, or however you wish to describe the
> lineage concept).  These are real, historical entities.  History happens.

      History happens, but the criteria used to group certain
historical events together for our convenience is a human invention.  All
cladistics has done is made the rules of grouping relatively simple.
Using the rules, defining groups may not be arbitrary, but the
establishment of the rules in the first place most certainly was.  
      Grouping by common descent is easier and more straightforward than
grouping by morphology, but it is not neccessarily any more useful, and
it certaintly isn't more real.     

> As to whether or not you wish our biological taxa to reflect evolutionary
> history rather than ecology or agricultural utility is a matter of taste.

     My point exactly.

> Ever since Darwin advocated (and Haeckel attempted) the use of "propinquity
> of descent" as the key feature of biological taxonomy, many biologists
> agreed that history should be a major aspect of our nomenclature.  Cladists
> argued that it should be THE major aspect of nomenclature.

> country "Australia" reflects the the natural, physical, non-human boundaries
> of the surface of the continent "Australia".

     The natural features exist, but the country itself is a human
invention.  Similarly, descent from a common ancestor occurs, but grouping
based on it is artificial.

> History happened.

     But it didn't group itself.  History is a continuum, and drawing the
borders at branching points and extinction is just another way of drawing 
convenient reference points.  
     
> >CLADISTS set the
> >rules that groups must begin with a node and end with extinction (or the 
> >present day- more on that later), not Nature.
> 
> And, of course, these events really did happen in the history of life, so it
> makes it nice and convenient.

     But they didn't group themselves.

> How about: clarifying some confusion with regards to early archosaurian
> divergence, especially with regards to functional anatomy?

      Or substitute "thecodont" for "early archosaur".  Tom-mae-to
to-mah-to.

> >ALL MEMBERS OF A MONOPHYLETIC CLADE DO NOT NECCESSARILY HAVE MORE SHARED
> >DERIVED CHARACTERS IN COMMON WITH EACH OTHER THEN THEY DO WITH SEPERATE
> >CLADE
> 
> Yep.  Your point being...?

      ....a monophyletic clade is not neccesarily a more useful
depiction of macroevolutionary trends then a paraphyletic one.  I realize
I am just covering the same old ground, but the Gauthier paper is going to
have to work pretty hard to convince me that any grouping of species,
regardless of how easily defined, is real.

LN Jeff
O-