>>>Chris Cogan: ...
I would guess that one reason some bacteria seem to produce more genetic
variations when they are in an insufficient-nutrient environment is that
the nutrients required to stabilize the DNA-replication process are in
short supply, and so it does not work as well, thus permitting more than
the usual amount of genetic variation to occur. Some would like to
attribute this increased variation to intelligence, but the simple
reduction in stabilization due to the lack of certain nutrients is a much
more elegant hypothesis because it does not require the introduction of
otherwise unseen intelligence, and because it automatically links the
reduction in nutrients to the increase in variation. Further, it lends
itself to empirical testing, whereas the ID alternative does not, except in
special cases.
************************************
DNAunion: FYI, Here is some information on adaptive mutations.
"In 1988 Cairns et al. showed the specificity of those mutation events. They
showed that a specific mutation will occur in high frequencies only when
needed to remove the selective pressure, i.e. during a selection for that
mutation and not in other stressful conditions, and that the former
selection, which triggers the specific mutation, does not trigger other
mutations. Cairns et al. concluded that those mutation were adaptive, i.e.
that the bacteria somehow mutate in order to adapt to the selective pressure.
These experiments and the conclusions triggered a furious debate in the
biological community and led to various additional experiments. The latter
ruled out several more conventional interpretations, and showed the active
role of the bacteria in the events of adaptive mutations (for details see
Ref. and references therein). " ((Prof. Eshel Ben-Jacob, School of Physics
and Astronomy, Raymond & Beverly Sackler Faculty of Exact Sciences, Tel-Aviv
University, Tel-Aviv 69978, ISRAEL,
http://star.tau.ac.il/~inon/wisdom1/node4.html#SECTION00040000000000000000)
HOWEVER...
"Researchers first noticed this happening in 1988 when John Cairns, then at
Harvard University, showed that mutation rates in the bacterium Escherichia
coli increased when the microbes needed to evolve new capabilities in order
to survive changes in their environment. At the time, it seemed that only
those genes directly involved with the adaptation changed, and this idea of
adaptive or directed evolution caused quite a stir.
But then last year, molecular geneticist Susan Rosenberg at Baylor College of
Medicine in Houston and her colleagues showed that mutation rates increase
throughout the genome, although only in a subset of the population. Another
group also found that more than just the relevant genes changed." (How the
Genome Readies Itself for Evolution, Elizabeth Pennisi, Science, vol 281,
Number 5380, Issue of 21 Aug 1998, p1131-1134)
DNAunion: So we are back to "adaptive" mutations being non-directed and
random.
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