[From Bruce Gregory (2000.1220.2009)]
Chris Cherpas (2000.12.1630 PT)
I agree that you can get accumulated changes via genetic
drift (without selection) but, then, I don't think of drift as
involving mutation, but rather as the outcome of recombination.
How do you imagine the variation originated if not by mutation? What is the
origin of the alleles you describe?
I agree in principle, and didn't mean to [over]state my proposal so
as to assume a pure adaptionist approach -- i.e., one that would preclude
other possibilities. Nor have I seen an argument that makes selective
mating an impossibility.
Indeed. I've always practiced it myself.
BG
On Wed, 20 Dec 2000, Bill Powers wrote to i. kurtzer, commenting on
kurtzer's information about the structure of the brain, "Isaac, I
am SO glad you are out there doing what you do."
Me too! --Phil R.
[From Chris Cherpas (2000.12.21.0100 PT)]
Chris Cherpas (2000.12.1630 PT)--
I agree that you can get accumulated changes via genetic
drift (without selection) but, then, I don't think of drift as
involving mutation, but rather as the outcome of recombination.
Bruce Gregory (2000.1220.2009)--
How do you imagine the variation originated if not by mutation? What is the
origin of the alleles you describe?
Mutation. I think there's a simple miscommunication here.
My point was that genetic drift is a possible outcome
of repeated recombinations, not mutations.
If we start with alleles a1, a2, and a3, and after several
recombinations lose all the a2s and a3s, leaving the population
fixed with only a1s, then we have genetic drift -- an outcome
which I would not describe as "genetic mutations that accumulate
in a particular direction" as in the following:
Chris Cherpas (2000.12.20.0740 PT)--
...I don't know of genetic mutations that accumulate in a
particular direction (e.g., bigger brain) without differential
reproduction.
...which was my reply to the following:
Bruce Gregory (2000.1220.0735)--
You are ignoring the possibility that genetic variation might lead to a
rapid increase in the size of the brain in the absence of selection
pressures. In other words, a fairly simple change in the genome might lead
to a large change in the phenotype. This can't be ruled out as far as I am
aware.
I incorrectly assumed you had mutation in mind when you wrote this,
but I now see that you were probably thinking of genetic drift.
Best regards,
cc
Chris,
[From Chris Cherpas (2000.12.20.1600 PT)]
So, mating preferences based on complex (multi-gene)
phenotypes (like more powerful brains) would be even more indicative
of fitness than simpler reproductive advertisements, like
florescent genitals.
Best regards,
cc
I sure hope you are not ruling out flourescent genitals sometime in our
bright future.
David
[From Chris Cherpas (2000.12.21.1940 PT)]
Chris Cherpas (2000.12.20.1600 PT)--
So, mating preferences based on complex (multi-gene)
phenotypes (like more powerful brains) would be even more indicative
of fitness than simpler reproductive advertisements, like
florescent genitals.
David Wolsk wrote:
I sure hope you are not ruling out flourescent genitals sometime
in our bright future.
I'm sorry to report that I think that we may have to
settle for such florescent ornamentation in the form
of an "extended phenotype" rather than something
strictly somatic.
Best regards,
cc
"Artificial intelligence is better than natural stupidity"