The body can be considered as a system of many redundant components, with aging as the result of progressive unrepaired damage to those components. This is a model that works very well. For further reading, you might look at the application of reliability theory to aging:
Bodies are complex systems and all complex systems can be prolonged in their period of prime operation by sufficiently diligent incremental repair. Developing a toolkit to do that for humans is the point of SENS the research program, with the point of SENS the advocacy program being to help people understand that the scientific community well understands in detail what needs repairing.
For more on the biochemistry of damage-that-causes-aging, explained for laypeople, you might look here:
> Anyone who paid attention during introductory statistics will recognize that your probability of survival to age t would follow a Poisson distribution, which means exponential decay (and not super-exponential decay).
Small correction: survival to time t under the lightning bolt scenario follows an exponential distribution. A Poisson distribution, besides for being discrete, has factorial decay, not exponential decay.
The longevity of the body is one thing, it is debatable whether or not it can be extended by a lot or a little (or at perhaps until the MTBF of a freak accident).
What I rarely see discussion of, however, are philosophical and psychological implications of "living indefinitely".
Even if the body is says relatively youthful, what about diseases of the mind? In other words, I am saying that in the same way that increasing life-span has uncovered a plethora of diseases that were previously unknown like cancer, is it possible that further increasing life span may uncover conditions (perhaps purely psychological) that we can't even imagine. Will people _want_ to live 100's of years?
To the extent we find bugs that cause the brain to stop working properly over time, we'll need to find and fix those. That falls under "problems we'd love to have".
As for the question of whether people want to live for hundreds of years: if you don't want to live longer, you can easily stop. A surprisingly large number of people seem to rationalize the lack of immortality by claiming people won't want to live forever, which strikes me as sour grapes. Given an actual solution that allows people to live forever, the question becomes "do you want to die?", and I seriously doubt many people will say "yes".
(Also, if you think of immortality as "hundreds of years", I think you need to recalibrate your scale. I'd like a lifetime measured on a cosmological time scale, and I have no problem conceiving of ways to spend that time.)
There is an interesting discussion of this in the Mars Trilogy by Kim Stanley Robinson. As people age well past a hundred, they can no longer remember most of their lives, and their cognitive function becomes progressively worse.
A friend used to say that most things he was warned about started with "Men over the age of 35..." and so once he hit 35 he would stop smoking, drinking, eating horribly etc. We would usually discuss such things on a smokey patio with beers.
He's just shy of 35 now, so we'll see ;) Sounds like your dad had a good sense of humor :)
The chance-of-death plots should be logarithmic, so we can tell if this exponential is really a good fit. On linear plots, it's hard to distinguish exponential decays from 1/x^n decays.
That graph showing survival probability as near 1 for age 0 can't be correct, since mortality is significantly higher in birth and immediately after, then drops for a long time, then shoots up again in old age. This is at least true in westernized countries that have medical care available.
Obviously, this is a simplification. Infants die for other reasons that you can think of to be different from the reasons for which old people die (e.g. cancer), and these reasons are being factored out of the graph.
Significantly higher relative to life expectancy of someone who makes it to 10 years old, but still incredibly low in the Western world. It's likely close enough to 0 that it just isn't visible on the graph.
Evolutionary theory would also suggest that we have some mechanism to ensure our deaths. Longer lifespans cause fewer generations per time period, resulting in less adaptability as a species.
Why would evolution need that? If grandpa is badly adapted, he'll starve/get eaten/etc; no need for a built-in kill switch. In fact, if there were a kill switch getting rid of it would be highly adaptive, if only because you could be around to defend your great-grandchildren.
(Of course, we do die. But the explanation looks more like "growing and reproducing quicker beats longevity" than like "planned obsolescence".)
But the degree to which aging is programmed - versus simply an unhappy stochastic decay due to diminishing selection pressures in later life - is a big and ongoing debate. Some species clearly have a lot of programming going on. For example, salmon age at a rate determined by the laziness of bears near to their particular rivers:
But there are equally good counter examples for many more species that suggest the situation is that evolution sets up to win the short race, front-loading as much as it can for early success, and then the selection pressure drops off after you had your shot at reproductive success. All that front-loading produces unpleasant later consequences as things fall apart - you're not set up for the long term.
The adaptive immune system is a good example of this - it's a system that could never run as evolved for an indefinite period of time. It's always going to crash and burn at some point, and that's somewhat a consequence of how it's evolved to run extremely effectively right out of the gate in early life:
This is a group selection argument. Why do you think the group selection pressure outweighs the selection pressure on individuals (which favors organisms who can produce the most offspring, and hence favors organisms who have long reproductive lives)?
In a somewhat unrelated idea. I've always wondered what the prospect of immortality, or longer average lifespans means in a world with rapid technological change. I'm borrowing from the idea of future shock.
Young people on average, seem to be more acceptant of new technology, where older seem to be less acceptant. Additionally, from personal experience; I think younger people think about problems differently as well which leads to new developments. It makes me wonder, even if our capabilities to develop new technology are growing (Kurzweil's theory of Accelerating change) perhaps the age of both the general population, and the engineers will cause some level of impedance.
Along the same lines, if a growing population requires growing technological change. And my concept is correct, that age reduces technological evolution, is it possible that it also reduces our ability to adapt, and a natural population balance occurs?
evolution is not about adaptability of a species, it's about adaptability of individuals (it's not a centralized decision taken for the well-being of a species, but rather a consequence of individuals having more chances to pass their genes than others. The lucky ones are more adaptive).
If you take 2 individuals and one dies sooner than the later, the alive one will have had more chances to pass his genes, so it's not adaptive to have mechanism to ensure our deaths.
I do not think ere is need to postulate a mechanism for death. I think death is a side effect of the evolutionary competition between keeping the current organism healthy and creating new organisms. One would want both, but lack of resources forces a 'choice'.
Apparently, it typically is better to create new organisms every now and then. That may just be energetically better or it may be because (in particular, sexual) reproduction allows for faster adaptation to changed circumstances
> Longer lifespans cause fewer generations per time period
This is not true though. It would be true assuming a constant population size or a single offspring. The number of children I have and the number of children my children have has nothing to do with how long we live.
I doubt it. If evolution really needed death then why does an immortal jelly-fish (http://en.wikipedia.org/wiki/Turritopsis_nutricula) exist? Granted their final life stage is a polyp which creates a new young medusa, but there theoretically could be a specimen that is 7 millions years old. Either way they wouldn't need to change for number of generations.
One of the sharpest changes (I guess a "point of inflection" it looks like?) seems to be at about 65, or the most common retirement age (here in the states at least). I wonder if there's a connection?
In hunter-gatherer societies, elders older than 60 have been observed as 1) looking healthy and 2) still being able to hunt, fish, trap, build, and pretty much everything else along with their younger counterparts. Perhaps at a slower pace, but they're generally far more fit than the modern world's old.
Pampered bodies grow sluggish through sloth, movement and their own weight exhausts them. - Seneca
In hunter-gatherer societies, elders older than 60 have been observed as 1) looking healthy and 2) still being able to hunt, fish, trap, build, and pretty much everything else along with their younger counterparts. Perhaps at a slower pace, but they're generally far more fit than the modern world's old.
When the conventional retirement age of 65 was established, few people made it much past 70. Social Security is in double trouble now because not only are we facing the retirement of the baby boomers, but they are living a lot longer too.
Silly question: If I'm understanding this correctly, doesn't this essentially mean that statistically it's possible to live forever? Or is there a point when you statistically have 100% probability of dying?
Sort of, depending on the model. For most models, if you take your "probability of dying in year X", and sum that over all the years from 0 to infinity, you'll get a 100% probability of dying at some point. The interesting thing is that there's no individual year with a 100% probability of dying - the certainty of death is just because "forever" is a really long time.
There are hypothetical distributions, though, where the sum total of probabilities is less than 100% - where some proportion of the population will, statistically, never die.
Of course this brings us to the real issue, which is that what the model says doesn't really matter - if the model disagrees with reality in extreme cases, reality wins.
This is just a model - a map of reality which may give some helpful predictions and insight about the territory, but is not the same thing as the territory (reality) itself. See, for instance, http://wiki.lesswrong.com/wiki/The_map_is_not_the_territory
Well, sure. Except the equation gives a 2 in 7 billion chance of even making it to 114 (note that in reality your odds are empirically better). The odds of reaching 136 are 1 in 10^86. For comparison, there are only 10^80 atoms in the universe...
Fun and interesting read. Personally though I think by only examining mortality rates then half the story has been missed. ie. life expectancy.
While intuitively we can see that the probability of dying in any given year increases with the more years you live, perhaps slightly more counter intuitively the longer you live then the longer your life expectancy is (rolling average obviously).
Would love to see the two put together somehow and charted.
[+] [-] reasonattlm|14 years ago|reply
http://www.fightaging.org/archives/2010/05/applying-reliabil...
http://en.wikipedia.org/wiki/Reliability_theory_of_aging_and...
Once you start to think along the lines of damage and repair, you inevitably end up in the SENS camp. It's the logical place to be.
http://www.fightaging.org/archives/2006/11/the-engineers-vie...
Bodies are complex systems and all complex systems can be prolonged in their period of prime operation by sufficiently diligent incremental repair. Developing a toolkit to do that for humans is the point of SENS the research program, with the point of SENS the advocacy program being to help people understand that the scientific community well understands in detail what needs repairing.
For more on the biochemistry of damage-that-causes-aging, explained for laypeople, you might look here:
http://www.sens.org/sens-research/research-themes
[+] [-] marchdown|14 years ago|reply
[+] [-] hallman76|14 years ago|reply
(I'm totally serious)
[+] [-] panic|14 years ago|reply
[+] [-] willchang|14 years ago|reply
Small correction: survival to time t under the lightning bolt scenario follows an exponential distribution. A Poisson distribution, besides for being discrete, has factorial decay, not exponential decay.
[+] [-] angdis|14 years ago|reply
What I rarely see discussion of, however, are philosophical and psychological implications of "living indefinitely".
Even if the body is says relatively youthful, what about diseases of the mind? In other words, I am saying that in the same way that increasing life-span has uncovered a plethora of diseases that were previously unknown like cancer, is it possible that further increasing life span may uncover conditions (perhaps purely psychological) that we can't even imagine. Will people _want_ to live 100's of years?
[+] [-] JoshTriplett|14 years ago|reply
As for the question of whether people want to live for hundreds of years: if you don't want to live longer, you can easily stop. A surprisingly large number of people seem to rationalize the lack of immortality by claiming people won't want to live forever, which strikes me as sour grapes. Given an actual solution that allows people to live forever, the question becomes "do you want to die?", and I seriously doubt many people will say "yes".
(Also, if you think of immortality as "hundreds of years", I think you need to recalibrate your scale. I'd like a lifetime measured on a cosmological time scale, and I have no problem conceiving of ways to spend that time.)
[+] [-] onemoreact|14 years ago|reply
[+] [-] Tossrock|14 years ago|reply
[+] [-] andrewflnr|14 years ago|reply
[+] [-] hessenwolf|14 years ago|reply
The Project Gutenberg EBook of The Big Trip Up Yonder, by Kurt Vonnegut
http://www.gutenberg.org/files/30240/30240-h/30240-h.htm
[+] [-] drumdance|14 years ago|reply
[+] [-] libraryatnight|14 years ago|reply
He's just shy of 35 now, so we'll see ;) Sounds like your dad had a good sense of humor :)
[+] [-] linuxminter|14 years ago|reply
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[+] [-] jessriedel|14 years ago|reply
[+] [-] kingkawn|14 years ago|reply
[+] [-] ArchD|14 years ago|reply
[+] [-] ajkessler|14 years ago|reply
[+] [-] benjoffe|14 years ago|reply
[+] [-] fragsworth|14 years ago|reply
[+] [-] JoachimSchipper|14 years ago|reply
(Of course, we do die. But the explanation looks more like "growing and reproducing quicker beats longevity" than like "planned obsolescence".)
[+] [-] reasonattlm|14 years ago|reply
http://www.fightaging.org/archives/2011/03/we-age-because-th...
But the degree to which aging is programmed - versus simply an unhappy stochastic decay due to diminishing selection pressures in later life - is a big and ongoing debate. Some species clearly have a lot of programming going on. For example, salmon age at a rate determined by the laziness of bears near to their particular rivers:
http://www.fightaging.org/archives/2007/12/bear-consumption-...
But there are equally good counter examples for many more species that suggest the situation is that evolution sets up to win the short race, front-loading as much as it can for early success, and then the selection pressure drops off after you had your shot at reproductive success. All that front-loading produces unpleasant later consequences as things fall apart - you're not set up for the long term.
The adaptive immune system is a good example of this - it's a system that could never run as evolved for an indefinite period of time. It's always going to crash and burn at some point, and that's somewhat a consequence of how it's evolved to run extremely effectively right out of the gate in early life:
http://www.fightaging.org/archives/2006/12/when-and-how-does...
For more reading on this topic, you might look into antagonistic pleiotropy - the premature optimization of the evolved world:
http://en.wikipedia.org/wiki/Antagonistic_pleiotropy_hypothe...
[+] [-] TheEzEzz|14 years ago|reply
[+] [-] swalsh|14 years ago|reply
Young people on average, seem to be more acceptant of new technology, where older seem to be less acceptant. Additionally, from personal experience; I think younger people think about problems differently as well which leads to new developments. It makes me wonder, even if our capabilities to develop new technology are growing (Kurzweil's theory of Accelerating change) perhaps the age of both the general population, and the engineers will cause some level of impedance.
Along the same lines, if a growing population requires growing technological change. And my concept is correct, that age reduces technological evolution, is it possible that it also reduces our ability to adapt, and a natural population balance occurs?
[+] [-] toumhi|14 years ago|reply
If you take 2 individuals and one dies sooner than the later, the alive one will have had more chances to pass his genes, so it's not adaptive to have mechanism to ensure our deaths.
[+] [-] Someone|14 years ago|reply
Apparently, it typically is better to create new organisms every now and then. That may just be energetically better or it may be because (in particular, sexual) reproduction allows for faster adaptation to changed circumstances
[+] [-] VMG|14 years ago|reply
Only if you assume the non-reproductive members are a net negative (grandparents becoming a burden)
[+] [-] makmanalp|14 years ago|reply
This is not true though. It would be true assuming a constant population size or a single offspring. The number of children I have and the number of children my children have has nothing to do with how long we live.
[+] [-] _Y_|14 years ago|reply
[+] [-] celticjames|14 years ago|reply
Not all animals are pre-programmed for an early death. I wonder if curve for these animals looks like the lightening bolt curve?
[+] [-] _gd3l|14 years ago|reply
In hunter-gatherer societies, elders older than 60 have been observed as 1) looking healthy and 2) still being able to hunt, fish, trap, build, and pretty much everything else along with their younger counterparts. Perhaps at a slower pace, but they're generally far more fit than the modern world's old.
Pampered bodies grow sluggish through sloth, movement and their own weight exhausts them. - Seneca
[+] [-] kiba|14 years ago|reply
Survivorship bias.
[+] [-] ams6110|14 years ago|reply
[+] [-] j_baker|14 years ago|reply
[+] [-] jbri|14 years ago|reply
There are hypothetical distributions, though, where the sum total of probabilities is less than 100% - where some proportion of the population will, statistically, never die.
Of course this brings us to the real issue, which is that what the model says doesn't really matter - if the model disagrees with reality in extreme cases, reality wins.
[+] [-] Jimmie|14 years ago|reply
[+] [-] Sharlin|14 years ago|reply
[+] [-] usaar333|14 years ago|reply
[+] [-] tikhonj|14 years ago|reply
[+] [-] redthrowaway|14 years ago|reply
[+] [-] ifearthenight|14 years ago|reply
While intuitively we can see that the probability of dying in any given year increases with the more years you live, perhaps slightly more counter intuitively the longer you live then the longer your life expectancy is (rolling average obviously).
Would love to see the two put together somehow and charted.
[+] [-] unknown|14 years ago|reply
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[+] [-] scotty79|14 years ago|reply
[+] [-] hezekiah|14 years ago|reply
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