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Re: Cladistics (was Sci. Am. - present)



In a message dated 98-02-25 14:03:38 EST, ashapli@erols.com writes:

<<  In math, you can only prove things BASED ON A SET OF ASSUMPTIONS.  You
ultimately cannot prove all the assumptions. >>

In math, you accept the "basic assumptions" (axioms) as not requiring proof,
and work from there. This is how you can prove propositions absolutely true or
absolutely false. For example, the statement "The integer six is prime" is
absolutely false, in any language, in any culture, anywhere in any universe.
Not even God can make six a prime number. Once you start requiring "proofs" of
everything, including such basic assumptions as that the world has an
objective existence independent of our ability to perceive it, then you wind
up in an unproductive, philosophical morass where nothing is provable, nothing
is real, and so forth.

With regard to cladistic analysis, I'm not satisfied with what I have read
about its ability to reproduce phylogeny successfully to the point where I
would grant it priority over other methods and tests. For example, if a
cladogram is presented that suggests there was biotic crossover between two
geographically separated regions, but geological evidence indicates that there
was no connection, I would be just as inclined to believe the cladistic
analysis is incorrect as to believe the geological evidence is wrong.
Cladists, however, would take the cladogram as a priori evidence of a
connection.

Given a 15-20% error rate in cladograms, I would have to see something like
30-40% of the taxa in the cladogram in both regions before I would agree that
the analysis is providing evidence of a connection. Less than that is just
noise.