From: CYMM (cymm@trinidad.net)
Date: Wed Jun 28 2000 - 12:35:37 MDT
CURT SAID: "...That's not an advantage to short life; it's an advantage to
early reproduction. It causes short lifespan only if early
reproduction and long life are somehow incompatible. In that
case, the incompatibility itself is the main casue of aging
- the tradeoff alone creates aging...."
CYMM SAYS: Curt, you're right of course...clumsy English again! But the
"incompatibility" is really (i) diminishing (cost/benefit) returns to
maintaining reproductive ability when viable progeny is extant... and (ii)
the negative benefits of loading the genepool with archaic combinations in
the face of rapid environmental change....
Some long lived complex species: tortoises; macaws; elephants; humans seem
to have real advantages for the coexistence in a population of several
generations.
But generational depth is almost nonexistent in many real populations... the
species seem to favour short life and develop interesting mechanisms to
foster death.
Lastly, in species where death by predation, misadventure etc. is high and
thus there is no real "danger" of loading the gene pool with oldies (...the
survival curve will be exponential anyway!!) we should sometimes see
long-lived non-ageing species. Maybe sea turtles; carp; and certain catfish
fit this model to a certain extent...
But then they STILL eventually age and die when captive reared in suitable
habitats. Is ageing different then... are they coming up against cellular
ageing constraints specific to the genetic complexities of being a metazoan?
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