Aging

I’m going to use words, rather than equations, so this is going to be a bit sloppy.

For our purposes, aging is the gradual decline of biological function that leads to increasing mortality with time.  Threescore and ten, and all that.

There are two senses in which aging is inevitable, but there is another sense in which it is not inevitable at all.

First, humans age.  You can’t find anybody who doesn’t.  Individuals from every population age, although not in exactly the same way -there are some racial differences.

Theoretical biology makes it quite clear that individuals ought to age.  Every organism faces tradeoffs between reproduction and repair.  In a world with hazards, such that every individual has a decreasing chance of survival over time,  the force of natural selection decreases with increasing age.  This means that perfect repair has a finite value, and  organisms that skimp on repair and instead apply those resources to increased reproduction will have a  greater reproductive rate – and so will win out.

Creatures in which there is no distinction between soma  and germ line,  such as prokaryotes, cannot make such tradeoffs between repair and reproduction – and apparently do not age.  Which should be a hint.

Again, thinking about hazards and the declining power of selection with age:  there’s not much point in paying extra for a car that never wears out if you’re about to enter it in a  demo derby.

In practice, this means that animals that face low exogenous hazards tend to age more slowly.  Turtles live a long time.  Porcupines live a good deal longer than other rodents.   Mainland opossums live only two years, but those on Sapelo Island,  off the cost of Georgia,  which has been predator-free for thousands of years, live three years.  Organisms whose reproductive output increases strongly with time, like sturgeons or trees,  tend to live longer.

The third way of looking at things is thermodynamics.  Is aging inevitable?  Certainly not.  As long as you have an external source of free energy, you can reduce entropy with enthalpy.  In other words,  despite what your kids may claim,  they really can clean up their rooms, as long as you feed them.  Disorder decreases locally.  It increases in the universe as a whole, mainly in the form  of high-entropy radiation going into outer space, but who really cares about that?  In principle there is no reason why people couldn’t live to be a billion years old, although that might entail some major modifications (and an extremely cautious lifestyle).

The third way of looking at things trumps  the other two.  People age, and evolutionary theory indicates that natural selection won’t produce ageless organisms, at least if their germ cells and body are distinct –  but  we could make it happen.

This might take a lot of work. If so, don’t count on seeing effective immortality any time soon, because society doesn’t put much effort into it. In part, this is because the powers that be don’t know understand the points I just made.   Sometimes I wonder what they do understand.

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74 Responses to Aging

  1. Michael Rose at UC Irvine is quite good on this subject. If you delay the first age of reproduction in each generation, you breed long-lived descendants. Perhaps you could also give the oldest male fruit flies the first crack at young fertile females?

    • little spoon says:

      If we kept selecting for older parents (like male 70, female 45), would we end up being longer lived or would we just end up with women who hit menopause later and men who were resistant against erectile dysfunction in old age?

      • John says:

        There is an ideal time that an individual needs to successfully reproduce, so if you delay the initial age that reproduction starts, you delay the point at which that time starts. Other aspects of fitness than having the parts that work are required for successful reproduction, so we would expect selection for those too.

      • It would probably cause a boom in the nanny industry. 😉

    • Richard Sharpe says:

      Are you suggesting some sort of Lamarkian effect (epigentics?) here or selecting for those that have a later first age of reproduction?

  2. a very knowing American says:

    Another way of putting it, also skipping the equations and being a little sloppy: Some people object to life extension on the grounds that it would contribute to population growth and overpopulation. It would, but not that much. If people had only enough kids to replace themselves, and then lived forever, population would grow toward infinity, but only at an arithmetic rate, rather than the really scary exponential rate. Stepping up fertility early in the life cycle (assuming the offspring survive) does a lot more to increase growth rates than extending the adult life cycle past a certain point. That’s why selection for living a really long time after the onset of reproduction is not a strong force.

    Our future as a species is likely to depend more on who’s having how many kids when (and maybe what they’re doing to those kids by way of genetic engineering and other enhancement) than on the Howard Families, or whatever the Methuselah Foundation can come up with.

    • little spoon says:

      ugh. It’s the most annoying thing. Why won’t people understand the simple and obvious need to invest in life extension? It’s so much more important than education or defense or healthcare for illegals- I’m sorry- aspiring citizens. It’s more important than understanding this HBD thing too. The Christians are a problem because they don’t fear death like they should as they believe in heaven. The liberals are a problem because they would actually put the theoretical good of the environment above preserving their own beings against oblivion.

      Why don’t more people possess the basic semblance of sanity needed to understand that we must invest in life extension ASAP so that we have at least some smidgen of hope in avoiding the complete annihilation of every aspect of our being? I mean, people get not to throw themselves off cliffs, so why not this?

      • I always smile when people say something is obvious and then don’t notice their assumptions. Just for openers: why should I shell out money to extend your life? A project by which “we all might might benefit” means a lot of people I don’t like living much longer. Is that a good tradeoff for me living longer? I doubt it. At minimum, you can’t claim it is obvious I should feel that way. Why should I acquire that religious value of yours? Secondly, I don’t notice that people’s personalities improve as they grow older. Mine included.

      • melendwyr says:

        Not to mention that there is a distinct difference between biological immortality and personal. Very likely, our brains cannot hold onto information indefinitely, and even if cells renewed themselves they wouldn’t be able to organize themselves into appropriate patterns with others. Brains aren’t like kidneys or livers.

      • sam says:

        > obvious need to invest in life extension?

        What is the obvious need? To me it seems progress and adaptation in many fields is driven by the old guard dying off.

        Can you imagine if Walter Kronkite was still anchoring the news and Eisenhower was still a major political actor? I strongly suspect that sort of ossification would be bad.

      • Yeah, Coolidge would be even better, but you have made me reconsider my position as well. I Like Ike. Our hearts are suddenly strangely warmed to the idea of life extension.

      • melendwyr says:

        Sure, you could have Ike indefinitely… but would you be willing to put up with having John Edgar Hoover in command of the FBI, forever?

  3. kai says:

    Not only that, but there is are 2 more out less trendy SF morale that go like this:
    -Immortality go hand in hand with quasi zero natality, leading to very slow population turnover and in turn, to a static society.
    -immortals get do old and bored that they wish to get old and die, immortality turn to a burden after 150 years or so.
    This is often considered as great wisdom, especially when the sf is reviewed in the mainstream…personally I have always considered those bogus arguments, often part of poor sf, and in line with the typical judéo-Christian belief that suffering is good and just…
    Basically defending the advantages of aging is like saying antibiotics deprive our youngs of the character-forming of tuberculosis (or better, STD…lot of loons actually think it is true for STD’s…so defending aging is in line with ambient craziness, after all…)

    • The main argument for the second morale is that our memory cannot cope with infinite lifespan. There is only so much information you can cram into brain so that you have to start selectively forget more and more things to make room from new experiences. Until to the point where you have to completely forget whole centuries of your life.
      In practice the brain in its current biological shape seems to simply get full – you will remember things from your childhood but forget everything from yesterday. Thus to have meaningful eternal/ultralong life the neuroanatomy of brain has to be modified – and at moment we do not have a slighest idea how to achieve that.

      • kai says:

        I do not agree on this. Not that we may start forgeting more after maybe 100y without aging, I agree that’s probable (no way to know for sure, there is no human who has ever attempted to store 100+ year in a non aging brain.). But I do not see how this would make the 100+ life non valuable. After all, I have forgoten a lot of trivia (and, I suppose, some non-trivial stuff too) in my 40y life already, and this do not make it worthless at all. As long as you can still have more or less normal memory function for your current activities, remembering the past less well is in no way a significant drawback of immortality. If anything, it makes the argument “living too long makes you bored” moot.
        But you seems to think that you will loose the ability to store new memories, not only slowly forget past events (brain get full). I do not believe it, and would like to hear your evidence for that (not linked to brain aging). It is true that most people have less clear memory of the 40-50 decade than the 20-30 one for example….just because a lot more of interresting things happen to you in the 20-30 decade than the 40-50. Especially nice things, which tend to be remembered better….If you don’t age, things would be different…

  4. Anon says:

    “In other words, despite what your kids may claim, they really can clean up their rooms, as long as you feed them.”
    I found this mental image delightful.

  5. JayMan says:

    Two things:

    A. Good to see the nod to individual/group variation in aging. Fits well with what James Thompson,

    Psychological comments: Intelligence in 2000 words

    …and I,

    IQ and Death | JayMan’s Blog

    …have said on the topic.

    B. Lobsters: apparently, their reproductive capacity increases with age, so lobsters are “functionally immortal” or something like that. That is, they don’t age like humans do:

    Lobster: Longevity – Wikipedia

    Well, a third thing:

    “In part, this is because the powers that be don’t know understand the points I just made. Sometimes I wonder what they do understand.”

    We forever wonder… 😉

  6. pauljaminet says:

    Very good idea. However, if this were the sole explanation, then why shouldn’t evolution evolve an epigenetic switch, in which availability of unlimited nourishment and safety implies unlimited lifespan, and only malnourishment / resource scarcity triggers loss of maintenance and repair and aging?

    A plausible explanation is that aging and death serves to dampen population fluctuations, preventing population booms and busts. On this view, aging will be positively selected if population busts have a chance of generating extinction.

    • gcochran9 says:

      No way. You’re invoking group selection – don’t do that.

      • pauljaminet says:

        I think you have misunderstood me. I like your hypothesis as an idea for why aging evolved in the first place. The question I’m asking is why evolution didn’t make aging an option, and instead made it a fixed feature of nearly all species. Aging exists — now why can’t it be abrogated if resources are rich? On your model, that would seem to be beneficial. Evolutionarily, it’s easy to turn features off. So presumably some creatures sampled this option. Yet they didn’t leave descendants.

        A long-term fitness benefit to aging is no more subject to the objections to group selection than is a long-term benefit to sexual reproduction. Aging, like sex, is common to nearly all life and is evolutionarily ancient. Sex, like aging, seems to lack immediate benefits for the individual who ages or who cannot reproduce all his genes.

        Empirically it is clear from the course of evolutionary history that creatures who age and creatures who reproduce sexually will generate more descendants hundreds of millions of years later than creatures who don’t. So there is clearly a fitness benefit.

        My explanation is: A lack of aging when resources are rich, in an environment where resource availability fluctuates, is like a Martingale betting system (http://en.wikipedia.org/wiki/Martingale_%28betting_system%29): you win nearly all the time — except when you go catastrophically bankrupt. Aging limits the size of the “bet”, ie the species population, when times are good, which reduces the risk of ecological catastrophe (a loss of all resources). Aging is like having a steady bet size at the casino. It doesn’t eliminate extinction events, but it reduces their likelihood.

      • You’re still invoking group selection. Fit strains will happily run the group into catastrophic bankruptcy, if they can. But immortality catastrophes don’t happen.

        “Evolutionarily, it’s easy to turn features off.” Entropy it isn’t a feature. Entropy is default. Resilience to ageing is a feature, and investment in it is fitness-reducing after a point.

      • Anonymous says:

        Plus, alleles that help early but harm late will tend to be selected for, which will make repairing ever more difficult as one ages.

  7. pauljaminet,

    I suspect that in our ancestral environment having had “unlimited nourishment and safety” in the recent past did not indicate with high probability that over the next year you would also have these conditions in part because of the difficulty of storing food. Also, since Malthusian pressures are going to stop any population from long living in conditions of “unlimited nourishment and safety”, such a trigger would likely never have time to evolve and if it did random mutations would decimate it during times at which the trigger couldn’t be activated.

    (I’m a huge fan of The Perfect Health Diet.)

    • pauljaminet says:

      Thanks Jim. I agree, “unlimited nourishment” is a thought experiment rather than an actual description of past environments. But given that there was some variability in nourishment, there’s still a question of whether creatures should evolve for radically less aging in environments with more nutrition, or only modestly less aging.

      To clarify, consider the distinction between (a) healthspan / realized lifespan (for humans, currently about 80 years) and (b) maximum lifespan (for humans, about 120 years). If aging is a fixed feature of our biology, maximum lifespan is not affected by resource availability — realized lifespan approaches maximum lifespan as the environment becomes favorable throughout life. But if evolution evolved a way to shut off aging when the environment was highly favorable, then maximum lifespan would not be a meaningful concept, since it would increase in favorable environments, and there would be no asymptotic lifespan to declare a “maximum.”

  8. AKarlin says:

    Fascinating to see this convergence of seemingly disparate strands of research – HBD, life extension/transhumanism, even the paleo diet (via John Durant above). This is why I love the blogosphere.

    The big problem with public sentiment on life extension is that many people are under the impression you would just continue falling apart, becoming a husk of your former self by the age of 150 and being kept alive by tubes. Obviously that is an unenviable existence. But it is not what actual life extension is about, of course. IMO, the futurists and transhumanists should focus more on the rejuvenation angle as opposed to the life extension angle. Though unfortunately, there is a lot of prejudice towards the very notion of rejuvenation because of its association with charlatanry throughout the ages – elixirs, philosopher’s stones, etc.

  9. sinij says:

    Immortal society would be very unideal. Social innovation will grind to halt. This might not be seen as a negative by immortals, but what other kinds of innovation will cease?

    Immortal society will also change society to be less cooperative. This will have all kinds of implications on how society governs itself.

    Now, I personally would want to live forever, but I certainly wouldn’t want to live forever in a society where everyone lives forever. Unless we can go exploring into space.

    • kai says:

      It is less ideal only if you use innovation rate to rank possible societies…if u use quality of life, then immortality is obviously better…most people don’t want to die, even more don’t want to age,
      at a very basic level, and fulfilling basic needs above previous levels is the main (only?) justification of progress…
      Regarding collaboration, why immortality would reduce it? It should increase individual cautiousness, at least a little bit (not as much as some think, at least on short term, because engaging in risky activities is more a hormone-dependent type of personality than a rational risk-benefit analysis…), but why less collaborative?

    • bleach says:

      this is what I figure. if biological immortality were achieved, i doubt it would be widely distributed. more likely it would remain the privilidge of a tiny, exploitative elite who would rule our descendants for eternity like the Olympians. the managerial state selects for sociopaths at the highest level, thank God none of them are “transhuman” and they will all be dead or infirm within a couple of decades. what else can stop them? imagine in Jobs had even a hundred more years to increase his wealth, with the lead he already had over the rest of us.. he’d be emperor of the world. no venal whim would go unappeased.

  10. Dan says:

    Could the Red Queen hypothesis argument for the evolution of sex also apply to aging? Really long living organisms would be easy prey for faster evolving parasites, no?

  11. there is an unproven theory that tubenoses are immortal. Though this seems like a stretch, I think it relevant.

  12. j3morecharacters says:

    “animals that face low exogenous hazards tend to age more slowly. Turtles live a long time.”

    Humans also live long, more than any Anthropoid and mammals (there may be exceptions). That means that we have low exogeneous hazards from many generations ago. Maybe the savannah was less dangerous than we imagine, predators seem to abhor human flesh.

    Eternity: Who wants to live forever? (Queen).I dont.

    • dave chamberlin says:

      “predators seem to abhor human flesh”
      I expect they found it quite delicious before the times when a man carried a pointed spear and made quite sure that it was pointed in the direction of any charging predator.

      • j3morecharacters says:

        No. Maneating tigers in India, for example, were very rare. Only toothless or those unable to catch faster animals tried anthropophagia. We stink.

      • Neil craig says:

        I suspect this is an evolutionary effect. We have been killing man eating tigers and their near kin for thousands of years. Killer whales occasionally eat humans, perhaps thinking of them as a variety of seal, but mankind has not been top of the food chain there for so long.

      • dave chamberlin says:

        Off the thread topic (sorry) but still hopefully interesting to Cochran and others. Following up and the subject area above, I’m guessing that once hominids started carrying sharpened spears they formed at first a parasitic relationship with apex predators such as lions, following them from kill to kill, which evolved into a symbiotic relationship. Allow me to explain. Hominids going back at least 400,000 years created perfectly balanced throwing spears, they have been found. How much earlier man learned to never leave home without a sharpened spear is anybodies guess but my guess is when man was intelligent enough to craft a sharp edged rock he used it to both sharpen spears and cut pieces of meat off a bone. Once lions learned the hard way that messing with a spear holding group of hominids wasn’t worth it, they became used to each others presence. Hominids greatly benefited by following lions from kill site to kill site which would be at first a parasitic relationship since there is no benefit to the lion. But give our ancestors of lets say one million years ago credit for learning the benefits of coexisting with lions whom (I’m suggesting) mutually preyed upon the beefy cornucopia of grazing animals that spread from the African savannah all the way up to the tundra. Lions feed on weakened prey, which is where our spear chucking ancestors come in. We weakened the grazing animal with a thrown spear, the lion finished the wounded animal off, we let the lion have his fill, and there was plenty left over for us. I am fascinated by the worlds earliest figurative sculpture, the 40,000 year old Lion Man. It is a beautifully carved piece of art that is half lion and half man. Now it is hypothesized this is the carving of an individual shaman. I’m hypothesizing that it is how a whole hunting tribe viewed themselves in their symbiotic relationship with the lion. The use of fire comes into this symbiotic relationship as well. Where there was enough precipitation to allow forest to replace grassland, we wouldn’t allow it, we used fire to create more grassland of better nutritional value. More grassland=more grazing animals=more food for man and beast.

      • Ilya says:

        @dave chamberlin: this (the story about symbiotic existence with lions) seems plausible. It also reminds me of a book by J.-H. Rosny aîné, “Quest for Fire,” which I enjoyed greatly back in my childhood.

      • Sideways says:

        It’s going to be interesting seeing how quickly the fear of humans is bred out of coyotes, and how soon that results in dead children.

      • Anonymous says:

        Thousands of people in India are eaten by tigers every year; and thousands in Botswana are eaten by lions every year. NatGeo had an interesting piece about rural Botswanans getting eaten recently.

      • Anonymous says:

        And that’s two countries! Predators certainly don’t “abhor” human flesh, but they apparently stick to rural meat, where there are no street lights.

  13. Anonymous says:

    The reason society puts less money into aging research than, for example, AIDS may be that those in power understand perfectly well that we can conquer it but that any sort of conquest of aging, from us all living 500 years and having children at the current rate to spending 430 senile would make the current organisation of society very difficult. Those in charge aren’t keen on a different organisational pattern,

    As an environmentalist once said when told that banning DDT was killing millions of African children “Its as good a way to get rid of them as any.”

    It all depends on whether those in charge are putting us on or really that stupid & like Twain I find either assumption incredible.

    • gcochran9 says:

      Come on, you think that the fools at the top have decided to eschew longevity – personal longevity – because they fear society-wide consequences? Anyone who understand thermodynamics and the evolutionary theory of senescence would understand this – but what fraction of the people running the show understand either one? They really don’t know.

      • Neil craig says:

        Yes, if they could and were smart enough they would. Silvio Berlusconi allegedly spends some of his billions on monkey glands etc and it looks like it is working (possibly only cosmetic) but I can’t think of anybody else rich or powerful, in the same situation. .

  14. Jim says:

    With typical rates of accidental deaths and homicides the elimination of all other causes of death would produce life expectancies in the thousands of years but nowhere near a billion. Lightning strikes alone would cut life expectancy down to a few million years.

    • gcochran9 says:

      Yes. Like I said, a very cautious lifestyle.

      • Anonymous says:

        Many might consider a very cautious lifestyle not worth living

      • kai says:

        indeed…so one way to increase lifespan is to select for cautiousness, I guess it would be one of the first outcome if a population is selected just for lifespan without checking the cause of death…could have happened when farming started and again, more recently, in the western world…Would not be surprised if it was a significant part of the increase of life expectancy, people being more cautious…

      • anneallen says:

        cautious folks would never fly to the moon, climb Everest or even fly a plane…how dismal

  15. dave chamberlin says:

    Greg says “don’t count on seeing effective immortality any time soon because society doesn’t put much effort into it.”
    Yes and no.
    If I made a TV ad tomorrow that sold “that miracle enzyme Telomerase that stops the aging process by repairing the normal wear and tear on your genes” I could get rich. I could go on with sales bullshit like “whats’ the secret that turtles and lobsters have for such long life? Telomerase! Stop aging today! Call 1-800-FOREVER.” My point isn’t that this would work but that there is enormous financial reward for any hint of a product that slows the aging process so I think society would put and is putting enormous effort into it. The problem isn’t effort it’s the complexity of the issue.

  16. Patrick Boyle says:

    I took a gerontology class at UC Berkeley in the eighties. I was long out of school at the time but it was for a part of a study I was doing at my job. The first time the professor came in the classroom everyone was stunned. He was a full professor with two full doctorates but he appeared to be no more than eighteen. No gray hair. No wrinkles. A gerontology professor who seems never to have aged has prima facie credibility.

    The first thing he said was ‘Some of you may never die’. I suspect however that by now several in that class are now dead. Most of my classmates were senior nurses in management and older than I was.

    The prof acted on his beliefs. He was into cryogenics. He had frozen the head of a daughter of a colleague. She had been in an automobile accident.

    But I now doubt that people will live much longer than they do now – at least as biological organisms. This year Google sells glasses that give you better user interface. This year your smart phone is really only a little smart. Soon Google will sell a direct connection to your brain. Soon your smart phone will be smarter than you are.

  17. Magus Janus says:

    Greg, I know a lot of people criticize Aubrey De Grey for being a bit wacko or overpromising on the results of potential life extension research (though this might be viewed as purposeful to acquire more investment).

    I was curious what your take is on him… is he a fraud/wackjob or is he onto something? and specifically, what do you find to be the most promising veins of research at the moment (or near future) for life extension? i.e. if you had a billion (or 10 bio) dollars to blow on this topic, where would you allocate them?

    • Anonymous says:

      mTOR is where the action is at! Making the body’s innate immune system work less hard & making the body think it has less nutrients available apparently do wonders for lifespan- but you reach reproductive maturity much later and are a total shrimp.

  18. RS says:

    > then why shouldn’t evolution evolve an epigenetic switch, in which availability of unlimited nourishment and safety implies unlimited lifespan

    Heard of war, murder? Even in the so called Pax Romana there was tons and tons of war: civil war.

    Nevertheless, I don’t think that disposes of your point entirely. I am somewhat inclined to agree with you.

    The thing is, those who had almost unlimited safety and nourishment – aristoi – tended to have very high amounts of sexual access, which tends to defuse the pressure to live longer. If you lay 15, or 50 different girls a year, what’s four years more or less? You are already incomparably fitter than the median, so, while it would indeed be better to live a few years more, the forces urging this are weak ones not strong ones. That does not resolve the paradox on the female side, though. But maybe there is no paradox on that side. A lot of different women have tended to belong to one male potentate. He shares out food and security over their large number. So they and their kids don’t, in fact, have nearly unlimited safety and nourishment: he does, they do not.

    • RS says:

      > The thing is, those who had almost unlimited safety and nourishment – aristoi – tended to have very high amounts of sexual access, which tends to defuse the pressure to live longer. If you lay 15, or 50 different girls a year, what’s four years more or less? You are already incomparably fitter than the median, so, while it would indeed be better to live a few years more, the forces urging this are weak ones not strong ones.

      Also, a better use of spare resources — better than increased biological self-repair — might be looking both ways before crossing the street, so to speak. Potentates have a way of getting whacked. As in man so in common chimp, but moreso. Most of the alphas and high lieutenants do not succeed in staying on top of their group for all that many years.

      • kai says:

        In part because they age, would they remain young and fit they could stay in top longer, the challengers really would have to be better, or lucky…not just the next generation…but we are back to the trade off Greg was speaking off….remaining fit for a long time, ie not aging, well consume resources, energy and redundant systems, and a careful lifestyle (the easiest mutation to increase life expectancy is decrease risk taking imho). A mutation which would trade this expense to get bigger, or stronger, or crazier (I.e. challenging stronger individuals, counting on luck and acceptance of injuries to prevail) will increase short term reproductive fitness while reducing life expectancy…
        I think you can prove that any trade off of this type coupled with irreducible accidental death ensure immortality would never be selected for…
        BTW I wonder if life expectancy of sexually reproducing organisms expressed in term of generations (time to reach sexual maturity, first reproduction) vary a lot? Probably not so much…

      • Anthony says:

        Kai –

        Humans would probably be an outlier. Looking up a few mammals on Wikipedia, the larger ones seem to be able to live for fewer generations. (However, the lifespans tend to be high-end, not mean, so judging by average age at death might flatten the relationship some.)

        Cat – 0.5 yr – 15 yr – 30x
        Dog – 0.75 yr – 12 yr – 16x
        Horse – 1.5 yr – 30 yr – 20x
        Chimpanzee – 8yr – 60yr – 7.5x
        Mouse – 50d – 750d – 15x
        Human – 14yr – 84yr – 6x
        Lion – 4yr – 20yr – 5x
        Bear (American brown) – 3yr – 21yr – 7x
        Wild boar – 1yr – 15yr – 15x

      • kai says:

        Hum, not only the lifespan seem a little bit high, but the generation time seems very low. Not only for humans (14 years the average generation time, in the sense it is the typical time at which a human produce a new human? i doubt it, except if homo sapiens has changed a lot biologically those last thousand years. It would mean, discarding father age, that the average age first first successful pregnancy would be 13. looks low, I would say at least 14-15, that would put the generation time around 16 and human lifespan 4-5 generation), but also for dogs (the only mammals I had a rough idea: 1y).

        Still, it’s a large spread, doesn’t looks like a better predictor than body weight. But we would need to check with non-mamals, to see if it gives anything useful…

  19. Patrick Boyle says:

    If serious life extension became possible it would be likely to be politically destabilizing. We know that many of the greatest leaders in world history made their out sized contributions because they lived so long. For example, Ramses II, Augustus Caesar, and Louis XIV. Longevity matters.

    One of the greatest benefits of well defined term limits is the reduction in political assassinations. Right now many political dissidents wait patiently for the day when Obama will leave office. Like Obama, Caligula, Nero and Commodus were initially popular. But Roman emperors had no well defined end point for the dissatisfied to wait for. When the Emperor’s popularity declined, the opposition began to sharpen their knives.

    Obama will leave office in just a few years and die perhaps in ten or fifteen years after that. Republicans can wait. But if he were capable of hanging around for another century or two, less patient voices might call for more prompt measures.

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  21. j3morecharacters says:

    Mi General: Punctuation.

  22. Sid says:

    I wonder how immortals would remember the past. I imagine that human memory would reach its storage limit before long, and that the immortals would forget increasingly vast amounts of memories just to be able to process new memories. Perhaps an immortal who had lived since 600 would have no recollection of, say, the 1220s. He would have horrific memories of the Fourth Crusade, and then have subsequent memories of the Black Death, all without being able to describe how one era transitioned to another.

    • kai says:

      Probably he would remember it like somebody having done extensive historical research, appart from some vivid personal experiences….Just like most remember their childhood: a few real memories, mixed with memories from stories told by their parents/friends and memories that started real but have been transformed by internal rehearsal, stories being told to ourselves. Everything so mixed you can not really tell which is which….

      Really, I do not think memory will really reach any storage limit, the natural memories are nothing like recordings, you forget, embellish or abstract a lot even with a normal lifespan, I do not see how it would be different or distressing with much longer lifespan/immortality.

  23. Jim says:

    Kai – Reductions in US mortality, which have been occuring over the last half century at roughly somewhat over 1% per year, have little to do with reduction in the accidental death rate.

  24. RS says:

    > In part because they age, would they remain young and fit they could stay in top longer, the challengers really would have to be better, or lucky…not just the next generation…but we are back to the trade off Greg was speaking off….

    I agree, in principle they could just stay alpha chimps indefinitely by dominating others for better nutriment, and thus staying bigger and more agile than the others.

    However, not only is there damage/death by falling out of a tree, not only is there damage/dethronement through a weaker party just getting lucky in fey fortune, there is also parasitism.

    Which might be a big one actually. Even though acute or chronic sickness may actually be one thing more that alphas and high lieutenants can deal with better than betas. On average. Thing is, its not average its stochastic. One day the alpha gets the flu while one of two key lieutenants is still convalescing…. voila. Also when a new parasite or strain enters a troop, the alpha is not necessarily the one best equipped genetically to control it, even if he does have higher phenotypic vigor than all the other chimps as of time zero.

    • RS says:

      Then there are reductions in warfare with certain neighbor groups because of ‘outmarriage’ ; intensified warfare with others . . . everything always shifting.

      Hostile groups do not target each individual in a hostile group uniformly, in human hunter peoples. There are those who are distant kin, who you are supposed to leave alone even if they belong to a hostile party, unless maybe they are just about to zap your own brother or something. Contrariwise, you’re the man if you can kill someone who has harmed your own narrow lineage ; random hostiles don’t count quite as much. All that is probably less documented in chimps, since you can’t ask them what they are doing, but by hypothesis I’d guess they act similarly.

      • kai says:

        I forget about sicknesses and parasites because, in most sf, immortality goes together with immunity to disease, parasites…usually with fast heading too, regeneration and sometimes resistance to poisoning…Basically, only way too die for an immortal is through severe trauma, that would kill quickly a normal human, lack of food/air/water or maybe some base broad-spectrum poisons.
        It makes partial sense, immortality must imply enhanced immune system and regeneration. But you are right, total immunity do not seems so logical , especially given germ fast evolution…on the other hand, I am not sure having an immortal dying of a fever would make a good sf story…

  25. Anonymous says:

    That seems to be Hydra vulgaris’ trick: it looks like it has separate germline & soma but doesn’t, it can undifferentiate any cells, it seems, when they suffer injury or start to go ‘bad.’ FOXO activity in H. vulgaris is basically nuts; but they can regenerate any time. Except they can’t really be immortal as the Cnidaria experts claim, or else the world’s rivers would be chock full of them, right?

    • kai says:

      biological immortality is not actual immortality….especially for a small hydra, plenty of critters that will eat it…

      • Anonymous says:

        True. We don’t actually know how they typically die, but we’re pretty sure it’s not predation. There must be some pathogens they catch.

  26. Pingback: linkfest – 12/15/13 | hbd* chick

  27. rob says:

    “Creatures in which there is no distinction between soma and germ line, such as prokaryotes, cannot make such tradeoffs between repair and reproduction – and apparently do not age. Which should be a hint.”

    A hint to the science or engineering? If it’s a clue to the latter, then we should find single-cell organisms as close to people as possible: which ain’t all that close. There are canine-derived infectious tumors. They’re effectively s&g. Do those cells age? maybe check out vitro cell cultures like HeLa cells. There must be some low-passage number clones frozen somewhere, so we could see if they age differently or more, than more heavily passaged lines.

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