Evolutionary necessity of senescence?
wsun at jeeves.ucsd.edu
Mon Feb 22 20:13:23 EST 1993
In article <C2o69z.FKs at usenet.ucs.indiana.edu> adpeters at sunflower.bio.indiana.edu (Andy Peters) writes:
> (1) Deleterious mutations which act later in life can build up
>(since selection against them is weak, they reach mutation-selection
>balance at a higher frequency than those acting early in life).
> (2) Phenotypes involving a tradeoff between early and late survival
>or reproduction can be selected for. So energy use that leads to
>later free-radical buildup, the use of certain proteins which are
>limited in quantity, etc., can increase early fitness, and the
>decrease in late fitness they cause isn't selected against strongly
>enough to counteract the early benefit.
> "God is a real estate developer / with offices around the nation
> They say one day he'll liquidate / his holdings on High
> I say it's all speculation." -- Michelle Shocked
These are descriptions of phenomena that are occurring at the
moment when man is not doing anything to affect his aging
process. For instance, the first argument considers the affect
of deleterious mutations. But theoretically, it is possible to
make the effect of mutations close to negligible. This may
require genetic engineering to make a better DNA repair system.
Or, it may involve controlling the cell cycle such that cells
can survive for much longer time without division (or DNA
replication). The second argument above considers the effect of
free-radical buildup. Again, this phenomenon can also be
controlled. We don't have the understanding or knowledge to
control these events yet. But already we can see how diet can
affect this phenomenon and decrease the chance of cancer.
In short, stopping aging is possible as long as there's input of
energy. Aging can be thought of as an increase in the entropy
of an organism. As long as there's energy input, a system can
be maintained at a steady state, and hence, aging can be
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