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Re: Dino Birds (was Re: Dinosaur = extinct animal)
In a message dated 7/12/99 2:20:50 PM EST, email@example.com writes:
<< In set theory, yes. Biologically, no. "Real" biological groups are
delimited by natural, external bounds that exist beyond human
subjectivity. Common ancestry forms such a basis - provided we agree
that evolution has occurred, divergence events form the lower bounds of
This is merely a philosophical difference about the definition of "real."
Suppose we have a clade A and an included clade B. Use whatever criteria you
like to decide whether a species belongs to A or more specifically to B. The
same criteria will also tell you at once whether the species belongs to taxon
A-B. A-B is just as real as either A or B.