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Re: the tonight show



In a message dated 1/10/01 6:19:47 PM EST, kinman@hotmail.com writes:

<< If "A" is the common ancestor of Bacterium "D" and Homo sapiens ("C"), 
 then "A" is clearly a more primitive bacterium.   Obviously A and D (both 
 bacteria) are far more closely related to one another than either of them is 
 to Homo sapiens, and there would an enormously long series of B's 
 (intermediate forms) separating Bacterium A from Homo sapiens.
       This extreme example makes very clear how deceptive cladistic 
 reasoning can be, especially when trying to equate "relatedness" with 
 cladistic "relationship".  This is not very apparent when you have only one 
 or two intermediates, but throw in a whole bunch of them and the example 
 Charles gave should be clear to all. >>

No, bacteria A and D simply >resemble< each other more than do bacterium A 
and Homo sapiens C. Homo sapiens C and bacterium D are, however, equally 
closely >related< to ancestral bacterium A (and thus to each other). A and D 
are both classified as bacteria because of their resemblance to one another, 
not by their phyletic separation. Here "bacteria" is a paraphyletic group, 
because it doesn't include its descendant taxon Homo sapiens.

I'm no fan of strictly cladistic taxonomy. I think it's quite legitimate, 
indeed, almost mandatory, to define some paraphyletic taxa according to 
resemblance and not according to phyletic relationship. I'm quite happy with 
a paraphyletic taxon Dinosauria from which Aves is removed (but even happier 
with a holophyletic taxon Aves that includes all the theropod dinosaurs, or 
even all the dinosaurs period).