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Re: The validity of cladograms (was Re: giant birds)



In a message dated 11/15/99 11:43:34 AM Pacific Standard Time, 
bettyc@flyinggoat.com writes:

> Why doesn't everyone use this one data set who uses Archie in a tree?
>  
>  I'll tell you why not.  The science is too early in development to have
>  everyone agree on the data in the bar code of Archeopteryx.   Until
>  EVERYONE agrees to use ONE data set for every species, you're going to
>  get different results using cladistics since your data is different.

Characters for a particular organism only have meaning when compared to 
characters in other organisms.  As long as we keep coming up with new 
theropods, and re-examining old ones, we will never arrive at a stable set of 
characters "defining" _Archaeopteryx_.

Besides that, it is not only the characters used that determine the topology 
of the tree, but also the taxa sampled.  So until we do the ultimate 
cladistic analysis, including every taxon that ever lived, the trees will 
never settle down completely, even with the same set of characters.


<Pet peeve>

What really bothers me is the growing profusion of clade names and clade 
definitions applied hastily to controversial or ill-supported groupings, 
where these names only make sense in reference to the particular tree 
topology found by that particular author.

</Pet peeve>

--Nick P.