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 Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=4561