Re: Evolution: A few questions

On Wed, 16 Jun 2004 17:01:43 +0200 Peter Ruest
<pruest@mail-ms.sunrise.ch> writes:
>
> Dick Fischer wrote:
> >Peter Ruest, wrote:
> >>The spontaneous generation of information by means of natural
> selection
> >>of random mutations does occur, but each such step of selection
> is just
> >>a yes/no "answer" of the environment to the "question", "Is this
> ok?" of
> >>the organism.
> >
> >I believe it is entirely possible that environment factors play an
> active
> >role in eliciting change in the genetic mix upon which selection
> can act.
>
> The influences of environmental factors on the evolutionary
> processes
> are more complex than simple mutation and selection, as can be seen
> in
> what follows. What I formulated above is just the simple basics of
> evolution. But whatever these more complex processes contribute to
> the
> phenotypes in a population, the environment's "answer" remains at
> most
> one bit - yes/no for each phenotypic result. The increased
> complexity of
> the "question" may be expected to slow down the fixation of any
> mutation
> (usually pleiotropic - having various effects) possibly selected, if
>
> any. Such more complex evolutionary steps hardly speed up the
> acquisition of information usable to build novel systems.
> Environmental
> factors tend to make evolution more difficult, not easier.
>
<snip>
I don't get the yes/no answer. If we have a dominant lethal or a neutral
mutation, it seems XOR fits. But most mutations are more graded in their
effect. I recall a study many years back that noted that the sickling
mutation distribution was slowly decreasing in the United States among
persons of African descent with the absence of endemic malaria compared
to those remaining in Africa. I don't recall the figures, but it was
given as a slow process. I suspect that there is also data on the
incidence of the various forms of thalassemia (same gene but various
mutations) which affect other populations. One may also imagine a highly
beneficial mutation or other genetic change, one which could sweep
through the population, whose bearer encounters a predator or a virulent
pathogen before reproducing. At the other end of possibility there is
genetic drift. Isn't the situation much more complex and subtle than a
binary response?

I also don't get the assumption that mutations are the determinative
factor. There are various forms of duplication of genes and chromosomes
and their control areas, along with recombinations. Color vision
apparently began with the duplication of a somatic gene for
photosensitivity to the X chromosome, followed by duplication of that
gene. I understand that some people have more than the two genes on their
Xs. Also, I recall reading of a New World monkey where some females have
different genes for visual pigments on their paired Xs, while males can
have only one kind of pigment. Despite the fact that I don't know much
about genetics and the mechanisms of evolution, it looks to me that the
situation is much more complicated.
Dave
Received on Thu Jun 17 15:37:43 2004