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From: keithd@cadovax.UUCP (Keith Doyle)
Newsgroups: net.origins
Subject: Re: Grasse'
Message-ID: <623@cadovax.UUCP>
Date: Fri, 17-May-85 14:33:24 EDT
Article-I.D.: cadovax.623
Posted: Fri May 17 14:33:24 1985
Date-Received: Fri, 24-May-85 20:02:05 EDT
References: <1072@uwmacc.UUCP>
Organization: Contel Cado, Torrance, CA
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[..............]
>> The information discovered also reveals that bacteria have not "stabilized":
>> they are in constant genetic flux, exchanging chromosomal material through
>> viruses and sex.   
>
>And they are still bacteria, which was his point.  [DuBois]
>
>>>   "What is the use of their unceasing mutations if they do not change?
>>> In sum, the mutations of bacteria and viruses are merely hereditary
>>> fluctuations around a median position; a swing to the right, a swing
>>> to the left, but no final evolutionary effect."  (p87)
>
>> How does he know they do not change?  How would they refrain from mutating?
>
>He does not mean that "they do not change because they do not mutate."
>He means that they mutate ad nauseum and they remain bacteria.
>
>> The idea of fluctuations around a local optimum is an important one for
>> explaining stability of species, but overlooks the possibility of new
>> and changing environments providing new local optimums.
>
>And since it is possible, it must be true?  The fallacy of the
>possible proof.

I might agree with you if it weren't for the other supporting evidence
that speciation occurs, i.e., all mammals have related bone structures,
other features etc., and their DNA is more closely related to each other
than to reptiles, fishes, bacteria, etc.

The mutations that we are all talking about, take place as changes in the
DNA.  Some changes may have profound effects on the organism, producing
an animal that may be unable to survive.  Other changes may be so slight
as to not be noticed at all.  Since DNA determines charateristics of
an organism, including species, there is no reason to believe that enough
mutations cannot occur over a period of time as to effectively transform
one species into another.  And, there is plenty of reason to believe that
species transformation CAN occur.  In fact, there is no evidence of dividing
lines that you can use to determine exactly where an animal becomes
a new species.  The only potential criteria that has been proposed, is that
different species cannot mate and produce fertile offspring, or perhaps cannot
mate and produce offspring at all.  Reproductive isolation is not a
particulary good criteria for determining species.  It may be, that the
difference in DNA required to prohibit cross-species reproduction may
actually be very slight, while the difference in DNA allowed while still
maintaining inter-fertility could be significant.  What then, is the
actual criteria for differing species?  Reproductive isolation may *encourage*
similar species to diverge, but it is not necessarily a mandate.  At the
same time, using some percentage of DNA similarity is probably not a
good mechanism for determining species.  What this all boils down to, is
that any percieved lines between species kind of dissolve, and perhaps
the entire notion of species is pretty darn fuzzy.  How do you tell when
yellow becomes green in the electromagnetic spectrum?  At 49% yellow and
51% green?  That may only be because you have an exact definition of what
yellow is and what green is.

Keith Doyle
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