From: John Clark (jonkc@worldnet.att.net)
Date: Tue Nov 23 1999 - 07:52:49 MST
J. R. Molloy <jr@shasta.com> On November 22, 1999 Wrote:
>At first it seemed to me that Dr. Pelicci had made sense when he opined that
>"there must be" a down side to mice with deactivated p66 genes, "because
>otherwise evolution would already have found this fix."
I would say that Dr. Pelicci still makes sense. All else being equal a long lived
mouse would have more opportunity to mate and pass on more genes to another
generation than his short lived cousin, but in the real would all else is not equal.
It takes energy to keep in good running order for a long time and you'll probably be
eaten by a cat before you get very old anyway, so the advantage is not great.
Mouse genes have found that the best strategy for increasing their number is to
put all their effort into a mouse's early days, so they created a vehicle that grows fast,
reproduces a lot, and dies young. If this was not true the p66 gene would never
have evolved in the first place.
To live longer a mouse does not need to evolve new genes, it just needs to drop
a gene it already has, however evolution has chosen not to do this. Evolution not
only evolved this life shorting gene it retained it for millions of years, that means
mutations that rendered p66 inoperable (and this must have happened often as it
does in all genes) did not do well in competition with non mutated working versions
of p66. Hence the speculation about the downside of the genetically engineered
Methuselah mice, speculation that p66 must somehow increase the fertility rates
of young mice.
John K Clark jonkc@att.net
>
> Curt Adams, Patrick Wilkens, and Joao Pedro de Magalhaes have generously
> informed me concerning the limitations of Evolution in regard to fixing or
> optimizing individual organisms. Thanks to all.
>
> As for the supposed ability of shorter life spans to accelerate the rate of
> Evolution by increasing the frequency of mutations over generations, this does
> not work because the attenuation of longevity which accompanies heightened
> mutability, in turn depresses the strength of the species (which, of course,
> includes individual group members), thereby rendering an over all disadvantage
> to short lived populations. This effect expands in species which depend on
> lengthened childhood (as Homo sapiens and elephants do) to reach their full
> (species specific) potential. I suppose that anyone well versed in complexity
> theory would have grokked this intuitively and quickly, but to this old head, it
> seemed quite counter-intuitive.
>
> Although making mice live longer has important implications for humans (no
> doubt), the Doogie Mice experiments (discussed in earlier threads on this list)
> probably have even more importance. Some of us need to get much smarter before
> we get much older.
> --J. R.
>
> --<>-- --<<<+>>>-- --<>--
>
> "May you live in eternity's sunrise,
> on the seashore of endless worlds."
> --Blake/Tagore
>
>
>
>
This archive was generated by hypermail 2.1.5 : Fri Nov 01 2002 - 15:05:50 MST