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Re: Linnean Classification and Creationism

Art Sippo claims that:

> To me, the ability to fix the time of such chromosomal rearragements
> makes better sense as the start of a true taxa than anatomic
> similarities/differences.

Your proposal presupposes that speciation events are always associated
with such chromosomal rearrangements.  That's not necessarily true.
Have such rearrangements occurred in mallard vs. pintail ducks (a form
of dinosaur I threw in just to remain relevant ;-)?  I don't know for
sure, but I wouldn't be at all surprised to find that the answer is
no, but they're clearly good (read distinct) biological species.

As for George's objection... The postmating isolation mechanism which
Art wrote about may represent an impenetrable barrier to gene flow
now, but it need not have always been that way.  That is, fertility
may (I should probably say "must") have been relatively low (but not
zero!) between the lineage which originally contained the
rearrangement and the parent population which did not.  To be more
concrete, Chimpanzee and human chromosomes can't currently line up
well enough to allow development to take place from the egg of a
chimp-human cross, but the chromosomes still partially align
themselves.  Before the lineages diverged to their current extent, the
alignment would have been better, and must have allowed for
interfertility.  Or we wouldn't be here.

Mickey Rowe     (rowe@lepomis.psych.upenn.edu)