At 08:58 AM 17/03/01 -0800, Robert wrote:
>For those of you who are unaware, the answers to the question of "why do
>organisms age?" are "the declining force of natural selection" and
>"antagonistic plieotropy".
I go off like an alarm clock every time I see this. I agree that
antagonistic pleiotropy is the principle answer (animals that foresake
later benefits for earlier ones survive better and procreate more reliably,
if only because predators and accidents get you sooner or later even if
you're in tip-top well-maintained shape).
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?"
"Well, you might think so in your youthful ignorance, you young lout, but
don't forget that evolution only works by passing down genes to the next
generation."
"What?? You're begging the question. If you stay alive and keep having
offspring, you're *one* of the next generation."
"No, see, once you've matured sufficiently to produce the first litter,
selection starts to discard you and focus on the kids."
"Why the hell should it? I mean, here I am, an immortal, fit as the day I
passed my maturity exams, and full of the guile and cunning of experience!"
"No, no, you're *old* and *used* now--your body is wearing out, while the
youngsters are scampering about, fit as fiddles."
"AAARRGHH. You're doing it again--begging the very question we started
with! Your body is only wearing out if you've let your repair mechanisms
run down. Why not maintain them?"
"Because-- Um. Erm, there are now a huge dispersed number of copies of the
genome in your body's trillions of cells, all with different portions
masked or activated differentially. It's not as easy as maintaining the
integrity of an ovum or sperm."
"I can believe that. But how do you *know* the cost-benefit profile works
out to the disadvantage of long-term maintenance? Maybe that's never been
tried, because the bad critters always eat you first."
"That sounds mildly plausible. But don't forget that a lot of those bad
critters are living *inside your poor suffering bod*! Bacteria, viruses,
prions--"
"Revolting. Hey, what side of the argument am I meant to be taking?"
"I can't remember. It's weird, this is just like talking to myself. You're
not-- Oh my god, you're not--"
"A renovated clone, yes. Sorry, uncle. Or is that nephew?"
Damien Broderick
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