X-Message-Number: 4561
From:  (Thomas Donaldson)
Subject: Re: CryoNet #4553 - #4556
Date: Tue, 27 Jun 1995 20:05:42 -0700 (PDT)

Hi Everyone!

As my friends know, I'm not a biologist by training, but thinking in a 
rigorous way about immortality requires all of us to learn all kinds of 
things, such as evolutionary biology. The most likely reason for birds 
living so long despite all the problems of high metabolic rates, etc is 
simply that they aren't normally as subject to disease and predation in 
the wild as many mammals of the same size. In general, lifespans track
the normal rate of death in a population: "old age" follows an age at
which most members would have already died of other factors.

I've felt for a long time that such ideas are important for immortalists.
Reason: if we are really going to increase our longevity, we need to know
whether or not some other factors will simply cancel out the increase. If
we lived 200 years ago, those "other factors" would be such things as 
typhoid and other diseases. But it looks right now that we can genuinely
take advantage of our increased longevity. Not only that, but if even 
current medicine and society continues at its present death rates, then
over some time human beings would live significantly longer than they do
now. (Our efforts aim at speeding up a change which would happen anyway).

I also believe (though perhaps with less foundation) that such things as
the wide variation of metabolic rates for animals with roughly the same
lifespan suggests that oxidation damage is a secondary effect of other
changes which cause aging, not a primary cause. If it were primary, we
wouldn't see birds living so long (for instance) ... or for that matter,
monkeys (which live longer than other animals of the metabolic rate). 
Just how that works is an open question; something stops us from making
the required amount of natural antioxidant chemicals which our bodies 
make when we are younger. Of course, if we knew what that something was,
we would have a much deeper understanding of aging than we do now.

Just a few thoughts on evolutionary biology ... 

And incidentally, evolutionary biology has only very weak connections to
the biochemical materials of which we are made. If we made ourselves of
silicon or diamond the same principles would continue to act.

			Long long life,

				Thomas Donaldson


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