In a message dated 3/17/01 9:12:57 PM, d.broderick@english.unimelb.edu.au
writes:
>But the `declining force of natural selection'? What *is* this:
>
>"Why does evolution let us die, uncle Robert? Why should a cooperating
>bunch of genes allow themselves to be thrown away just because the bodies
>they've built, and run, wear out? Shouldn't a few of them stumble on
>enhanced maintenance mechanisms like the ones that keep germ lines nice
>and clean?"
The later in life an improvement helps, the less expected benefit it provides
for
its carriers and thus the genes that create it - because of the increasing
chance the organism died for some unavoidable reason. Nifty genetic
systems are always being corroded by mutation-drift. For any given gene,
a given benefit plus a given mutation rate results in it being present
in a certain portion of the population. As the benefit occurs later and
later, it has to be larger to occur at the same rate. Late enough, and
even rescue from certain death isn't enough to keep the gene common.
So the answer is, yes, late-life benefit mutations occur, but they're rarely
common because the average benefit to carriers is low.
This archive was generated by hypermail 2b30 : Mon May 28 2001 - 09:59:41 MDT