ageing as an evolutionary force

french at RUST.ZSO.DEC.COM french at RUST.ZSO.DEC.COM
Thu Apr 16 18:05:55 EST 1992

> In terms of long lived, slow critters. Why wouldn't natural selection
> work on animals with an immortality gene in addition to those
> critters without such a gene?

Immortal critters with a prolonged period of fertility would tend to
stableize the gene pool by mixing their genes back in.  This can 
easily be seen by considering what would happen, in the extreme case, 
if the critters were to remain fertile for a million years.  

If the critters had an ordinary fertility period, but were otherwise
immortal, then selection would favor those immortal critters that
improved the suvival rate of their offspring.  One would also expect
that there would be an optimal length of time that the critters would
live past reproductive senencense - this would be a function of the 
benefits versus costs of maintaining living parents and grandparents. 

What puzzles me is that, if lifespans are set at less than their maximum
possible value, then why do older animals gradually become enfeebled?
It seems like it would be much more efficient for the species if older
animals were maintained in a robust state until their allotted times
were up.

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