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Re: Linnean Classification and Creationism



In a message dated 95-12-19 13:18:43 EST,Mickey writes:

>>(Art Sippo) 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.
>
>(Mickey)Your proposal presupposes that speciation events are always
associated
>with such chromosomal rearrangements.  

I specifically avoided the word "species" in that sentence and used "taxa"
(oops! should have been taxon) to avoid this problem.  A specie is a
collection of organisms which shares a common gene pool.  Various types of
reproductive isolation (eg. geographical, behavioral, phyiological, or
genetic) may isolate the members of a specie from other similar organisms.
 These barriers do not necessarily mean that successful reproduction is not
possible with members of other closely related species but only that it
doesn't normally happen.  I was really proposing this mechanism of
chromosomal rearragement as a more rational approach to defining true
"genera" since --to my knowledge-- "reproduction"  (whether  of a healthy or
deformed offspring) is not possible outside of the same genus.  

I would also say that I do not agree with the idea that after the
rearragement has occurred there could be successful "reversion" to the parent
type.  As far as I know the rearrangements are irreversible and do not
spontaneously correct themselves. It may be a thermodynamic thing.  There are
so many safeguards in meiosis and related processes that a rearrangement
could only occur if it were strongly favored biochemically.  While it COULD
go backwards in theory, most such reactions in the cell do not occur anywhere
near equilibrium and should move predominantly in one direction only.

Art