From: Ray Recchia (rrecchia@mail.clarityconnect.com)
Date: Wed 07 May 2003 - 11:44:42 GMT
At 08:25 PM 5/6/2003 -0700, you wrote:
>oh, very nice lawrence. hm, if it will take around 300,000 generations to
>re-de-evolve, even at worst, and the environmental change that put the
>pressure on de-evolution is severe and sudden, the poor little organisms are
>going to go extinct. what an awful scenario! thank god there are no real
>life situations where this actually happens or we might not have termites.
>hm, even if it were to take only 2 generations to get a guaranteed
>beneficial point mutation in all of the genes that would be required to
>support the correct camouflage (yes, that's so likely to happen), the
>organism will die anyway because evolution only works in small intervals,
>not in an environment that changes drastically in very little time. isn't
>that why fish and insects go extinct? good luck with this hypothesis.
>
>always, sabrina
>
>
I suspect that Lawry's numbers are a bit off. If his numbers were correct,
even quickly reproducing species would take billions of years to evolve. My
recollection (from sixteen years ago) is that there are 100 or so mutations
for every cell division. I can't remember how many cell divisions there
are between generations but combining that rate with a few dozen or so
rounds of cell division and you end up with much quicker
results. Homologous recombination is also a fairly common occurrence
during reproduction. A particular visible trait can be controlled by
dozens of genes located on various chromosomes and reshuffling of both
chromosomes and parts of chromosomes can introduce substantial variation.
I was thinking of something as a sort of precursor to polyphenism.
Polyphenism requires (in our hypothetical) not only genes for spots and
plain grey, but also genes for recognizing the environmental difference and
switching on or off different versions in appropriate circumstances, but in
the particular example I was thinking of that might be what was occurring.
But it's all a bit off the beaten path of cultural evolution anyway.
Ray
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