On Wed, Apr 17, 2013  meekerdb <meeke...@verizon.net> wrote:

> It's been proposed that the susceptibility to mutation is itself a
> characteristic subject to natural selection.
>

If a animal is undergoing stress (too hot, too cold, too thirsty, too
hungry whatever) that means there is something about it that is not well
adapted to its environment; I can imagine a gene that in times of stress
would switch on and produce a chemical that increases the rate of random
mutation in the genes of the offspring of that stressed animal. Most of the
offspring would have mutated in the wrong direction and die but they would
have probably died anyway because they would have been as poorly adapted as
there parent was, but if the mutational effect was not too strong (even if
it's in the right direction you can change things too far) it could
increase the likelihood that at least one of its children would be better
adapted than its parent. However I maintain that such a stress induced
mutation producing gene has had no significant effect on the history of
life, at least not in animals that reproduce sexually.

Such a stress-mutation gene has never been found in a sexual animal and
it's easy to see why. In sex all the genes are not inherited in one big
package but are shuffled around with the genes of the other parent, so a
animal that was lucky enough to inherit the good genes produced by the
hypothetical stress-mutation gene but not the stress-mutation gene itself
would do just as well or better than a animal that got both the good genes
and the stress-mutation gene that is no longer active because the animal is
no longer under stress. So even if such a stress-mutation gene did occur in
one individual in a population it would vanish in just a few generations
from the gene pool. Natural Selection doesn't figure  "I better keep that
stress-mutation gene because even though there is no stress now that could
change and such a gene might come in handy in the future".  Evolution has
no foresight and can't think and all that matters to it is what's happening
right here right now.

  John K Clark

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