X-Message-Number: 11843 From: Thomas Donaldson <> Subject: about aging and evolutionary reasons for it Date: Sat, 29 May 1999 00:59:26 +1000 (EST) To Yvan Bozzonetti: There is and has been for some time a good evolutionary theory to explain the existence of aging. I've actually discussed this several times, but here are a few sources: GC Williams, Pleiotropy, natural selection, and the evolution of senescence, EVOLUTION 11(1957) 398-411 GC Williams has published a number of more popular things lately but so far as I know he hasn't discussed aging in any popular source. Two other researchers into evolution have looked in more detail at the basic ideas which originated with Williams: JM Emlen, Age specificity and ecological theory, ECOLOGY 51(4)(1970) 588-601 WD Hamilton, The moulding of senescence by natural selection, JOURNAL OF THEORETICAL BIOLOGY 12(1966) 12-45. There have been a number of experiments looking at evolutionary factors since then. The above are quite basic papers. The fundamental idea that Williams pointed out was that evolution does not act on creatures which have already died. To explain that point more clearly, most animal populations die in nature some time before they would come close to becoming "old" in our terms. Even most human beings had a similar fate until quite recently, though people in the upper classes did live longer. This means that you become old basically because the systems needed to keep you in top shape at high ages never had any pressure to evolve to do so at high ages... you'd already died of other things (diseases, accidents, etc etc). It also has a corollary: if we maintain our current lifespans, then even without any special effort (not that this would help us!) we would eventually evolve to live long enough so that we would not naturally become old at, say, 100, but only at ages most people would have died by accident. (I'm not in favor of doing this, of course, but the frequent occurrence of old age NOW is a sign that we're under slow evolutionary pressure to live longer). Some people have argued that aging has some positive effects and is supported by evolution. Hamilton and others have looked at the mathematics of this in detail, and basically find (as with most such things) that yes, we can make up extreme circumstances which do not fit our present situation at all but in which there really are evolutionary reasons for aging. Does that mean anything? Well, it means that with lots of imagination we can come up with situations quite unlike our own. Naturally I want advances which apply to ME, not to any putative descendants several generations from now. These ideas do not tell us to sit by and let evolution take its course. What they do provide is an answer to all those people who still think that aging and death is somehow favorable "to the species". No, it is not at all. Finally, I will add that even some increase is helpful, because we can then hope to live longer and get further increases. At the same time, as someone who has been both concerned with this problem, and reading the science about it for decades, I strongly suspect that abolishing aging entirely will ultimately require some redesign. Not that such redesign is bad in any way ...what does evolution do, after all? But we'd want to do it by taking things in hand ourselves. Best and long long life, Thomas Donaldson Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=11843