The idea of immortal creatures, be they vampires, ghosts, or demi-gods, is popular in fiction, but I can't recall any fiction where the idea of widespread physical immortality was dealt with on a common scale or at a basic economic level.

If humans all were biologically immortal - that is, they would not undergo senescence and would die only to starvation/suffocation, physical damage, disease, etc., would it make a big difference to the world as it is today?

The idea that we could be crowded out by steadily increasing numbers of ageless ancestors or permanently barred from promotion by that boss that won't ever need to retire is amusing, but my gut says no - people don't exactly drop dead of old age as it is, but from things like cancer or accidents. I'm assuming we'd see a shift upward in life spans among select areas of the population, maybe the odd thousand-year-old billionaire, maybe heart disease would lose its spot on the 'most likely to kill humans' chart, but other than that I'm not sure we're all that hard to kill off.

But that could simply be because I haven't considered all the facts yet (biological, psychological, social, or economic) so I'm interested in other people's thoughts - preferably not wild, fantastical, chicken-little ones - but from the consideration of the issue as if it were a real thing.

What happens when after a few hundred years you're out of space in your memory? Would only the most vivid memories stay in?

As for the boss who never retires, I doubt that biological immortals would want to retain the same job for thousands of years in any case, even as a boss, and if the underling is immortal too, then what's the rush? Moreover, if we can have mandatory retirement ages today (even for people who are perfectly healthy), then similar laws could conceivably ensure some kind of rotation of immortal professionals. As in, you've got to "retire" for so and so many years, only instead of dying a few years later, you go get a new job somewhere else.

Immortality would be more problematic with regards to population growth. Most likely society would have to implement draconian population control mechanisms of some sort; possibly mandatory vasectomy or some such, possibly with mandatory abortion for unplanned children. That might be a problem to maintain/implement (see: China for how that can go wrong).

A society of immortals could very easily become stagnant WRT social and technological development.

That might be a problem. It's all wrapped up in why my gut says no - I can envision people not being able to deal with the problems of extended life via practical means other than, well, assisted suicide once people get unhappy or uncomfortable enough.

Fair point, but are the laws in place to force people out of jobs? And is it because of economic concerns or health concerns?

We'd get to a crisis sooner, but we seem to be doing fairly well at getting there with good old fashioned mortal humans. I don't know if it would be a new problem, or just a faster problem. Besides which, my major doubt comes from the fact that even without sensecence, I don't think we'd all live problematically long. Sooner or later, if you lived long enough, a drunk driver or angry cuckolded husband or just mis-stepped ladder rung is going to get you. To say nothing of places like the shitholes of Africa where plain old disease and starvation keeps people from living long enough to worry about living too long.

Why?

In a few hundred years of life, a lot of bad memories accumulate. So I assume that psychologists and manufacturers of antidepressants see a growth in business. So instead of old people's homes, we see something like homes of people so bummed out that they're on pills constantly and need care.

While it's ostensibly for health concerns, it does seem like it's also for social/political concerns, seeing as changes to the retirement age being unpopular. The point is, it's possible to do.

This is true, though an elimination of the death rate due to old age is still going to be a significant reduction to the death rate overall. You're going to have to reduce the birth rate by the same amount to achieve equilibrium (and in many places, you would have to reduce it by more).

Because people usually don't like changes to society beyond their comfort zone. Significant changes to social philosophy and general attitude often (though not always) come with each new generation, people often only change their minds due to social pressure, or when they're forced to do so for whatever practical reason. Notice how people's stance on social political positions correlate strongly with age.

Hmmm.

One big unanswered question here is "what does it mean to die of old age?"

Fifty or years ago, we'd talk about men dying of old age when they had so many medical conditions that they fell sick and died quickly because the medical technology of the time wasn't able to keep them going. They could hook you up to an IV or oxygen, but if you needed three different drugs to keep your heart beating, a dialysis machine to keep your blood from overloading with poisons, and something else entirely to keep your lungs from freezing up... you were out of luck and would probably die quickly, since the stuff you needed hadn't been invented yet. Rather than dissect the exact cause of death, we'd say "Bob died of old age."

Now we talk about people dying of congestive heart failure, for example- which is a very typical 'old age' death, in that without modern medical facilities someone suffering from it just breaks down and dies in a matter of hours. But if we want to break it down that way, no one dies of "old age." People die of heart failure, or cancer, or liver failure, or complications caused by treatment of the cancer stopping their heart, or complications of the treatment of the heart failure caused by the treatment of the liver failure, or complications of the amputation that was caused by the lack of blood flow caused by complications of the treatment of the heart failure caused by the treatment of the liver failure, or... you get the idea.

So if we make people 'unaging,' they still get sick, right? What is the risk of illness? Could we figure out expected mortality rates just by looking at what the actuarial tables look like for a healthy forty year old now?

Which medical conditions are considered part of aging, and which aren't? Do 'unaging' women still undergo menopause? If they do, does their bone mineral density still decrease after menopause?

This depends on how you define disease. Cancer is a part of the aging process. Accumulated mutations over the course of a lifetime eventually break down the error checking and growth inhibition mechanisms of cells. Even if you say we are immune to carcinogens, it will still happen naturally, just at a lower rate. There are certain processes that you have to eliminate for this to work that are entirely endogenous. Even people with good cardiovascular health have cholesteral buildup in blood vessels.

The telomeres get cut off the ends of chromosomes a little bit with every cell division which puts a hard limit on how many times a given line of cells can divide, resulting in eventual death by multiple organ failure. If that is what you are stopping... well...

You still have a massive increase in the r, the intrinsic rate of increase. So our population will never stop growing. There will be no level out of our population in ~2040 due to an aging population dying off. The end result will be a huge overshoot in carrying capacity followed by famine and starvation. You know, if we are not doomed to see that anyway because of degradation of carrying capacity itself.

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GALE Force Biological Agent/
BOTM/Great Dolphin Conspiracy/
Herpetology and Evolutionary Biology Subdirector:SD.net Dept. of Biological Sciences

There is Grandeur in the View of Life; it fills me with a Deep Wonder, and Intense Cynicism.

Actually, our brains are wired such that they tend to bury the bad memories and make them difficult to recall. The good ones are easier to recall, and will invariably be the first thing you think of when you reminisce about something. That's what we have nostalgia; college seems like it was so much fun when all you remember is hanging out with friends, going to parties, and acing exams. If you make the effort to dig a little deeper, then you start dragging up the anxiety, the lonely nights, the misery of studying, etc.

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"There is a principle which is a bar against all information, which is proof against all arguments and which cannot fail to keep a man in everlasting ignorance--that principle is contempt prior to investigation." -Herbert Spencer

"Against stupidity the gods themselves contend in vain." - Schiller, Die Jungfrau von Orleans, III vi.

I would take a look at Peter F. Hamilton's Pandora's Star and Judas Unchained. Both deal with immortality and go into some of the possible consequences of human immortality. (The focus isn't on immortality, but it does play a large role in the setting/plot/characters)

One of the interesting things about the series is how immortality affects the justice system. When people are biologically immortal is it immoral to use the death penalty when you have all the time in the world to rework them into society? How much more terrible is murder or manslaughter when death is not unavoidable?

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If it waddles like a duck and it quacks like a duck, it's a KV-5.
Vote Electron Standard, vote Tron Paul 2012

A lot depends on the details.

Are these immortals immune to illness, or can they still suffer bacterial, viral, and other such illnesses? Is the body maintained at a certain base level of fitness or do they still deteriorate over time - in other words, wrinkle free with strong bones forever or getting prune-faced and fragile? Are we also assuming that whatever magic makes humans immortals also greatly reduces fertility at the same time or not?

So many assumptions in society are based on the notion of aging and death. With everyone immortal (and presumably healthy) there is no longer a need for retirement planning, though of course plenty of people will want to accumulate wealth. Accidental death will still occur - perhaps even more often than now as jaded people seek new forms of stimulation. There will probably also be people obsessed with safety, basically the opposite extreme. Technological innovation may not slow significantly, but social changes might well slow down. Some people will spend their immensely long lives learning new things. Others will find a comfortable niche and stay there a thousand years. And some dysfunctional people will make the same mistakes and live in the same horrific circumstances for centuries or millennia.

I wanted to be clear in the OP that I was largely eliminating senescence. No magic or invulnerability or immunities to disease or changes to fertility - everything else is what you find among average healthy adults.

But there's a blurry line between "magic immunity to aging" and "magic immunity to disease" because the mechanisms that make us get sick when we get old are the mechanisms that make us old.

Like, do our genes stop gradually mutating over time? Do we stop having cholesterol buildup? Is that part of senescence, or not?

It's reasonable to say that it's an unsolvable question, even if that isn't satisfactory to one's curiosity. If I had the free time, I'd probably start by pouring over some general statistics to separate causes of death into categories closely relevant to age and aging.

As an aside, this whole curiosity started from very child-like reasoning - while on a discussion of aging and trying to explain organisms that appear to be negligibly senescent to a five-year old, and being asked why they don't overwhelm their environments (not in those words, but more along the lines of "why aren't there turtles everywhere if they don't have to get old and die?".

Well...

Turtles reproduce slowly, they have appalling (by human standards) infant mortality due to their lay-eggs-and-walk-away approach to parenthood so few reach adulthood, and other critters do eat them.

Thing is, humans carefully guard and nurture their offspring (well, most of 'em) and have eliminated most of their predators. This makes up for our own relatively low fertility and infrequent reproduction compared to some other species and has led to us being a bit of a plague upon the world. Add in immortality and our overpopulation just gets a lot worse.

Because it takes them that 30-250 year lifespan to produce enough offspring to replace themselves. That is why. They also DO get old and die. It just takes a loooooong time. They eventually (at 30-250 years old, depending on the species) do die from old age. Cancers, organ failure etc. However, what does not happen is reproductive senescence. Females have a HUGE number of gametes in their germ line and they can keep producing viable offspring until the day before they die of old age at the age of 250.

This is actually kind of important. Humans have a long lifespan compared to most things because despite their small number of offspring, they take care of those offspring for ~20 years, and then assist in the raising of their grandchildren after they have themselves stopped being capable of reproduction. In most species, there is no selection to prevent body aging after reproduction has stopped. In humans, because of prolonged parental care that transcends generational boundaries, there is. Turtles are at that semi-hard limit on how far the genome can hold off its own decay from mutation and cell division because they simply do not undergo reproductive senescence.

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GALE Force Biological Agent/
BOTM/Great Dolphin Conspiracy/
Herpetology and Evolutionary Biology Subdirector:SD.net Dept. of Biological Sciences

There is Grandeur in the View of Life; it fills me with a Deep Wonder, and Intense Cynicism.

This is touched on a bit in the GURPS Transhuman Space RPG setting. Economically, more and more of the world's wealth is locked up in the hands of the first immortals, since wealth tends to beget more wealth. Also, an ageless workforce (plus automation) means more and more of the younger generations not only don't have jobs, but will likely never have jobs. This results in various social problems of greater or lesser degree, depending on the society in question.

Wouldn't that just cause a revolution or emergence of socialist system? Or even deliberately Luddite society?

As for question of breeding, well, if China could do it with mortals, I see no problem with a state inhabited by immortals, since now you have incentive to spend child money on yourself and wait a bit until you can have your own. Some simple solution, such as steep child tax would have sufficed, though, finding an ethical one that doesn't favour one social group could be a problem.

That's what happens to you right now. You only ever actually remember a very tiny subset of everything you've experienced in your life. Everything else is your brain just taking what few symbols it actually stores and using them to invent scenes when you want to remember something (think of your experiences as a video game. It looks and feels immersive, but that building you're killin' dudes in has been broken down to a map of triangles, some bounding rules, and a handful of textures procedurally mapped onto those mathematically generated surfaces to allow the game content to fit onto a DVD.) It's just like your skill-set. You only remember the skills you use the most frequently. Everything else just sortof falls by the wayside as your brain redirects finite resources to learning other things. The brain may have a stupendous number of neurons and potential connections available to it, but it uses them in a computationally inefficient way, as a given skill or memory requires a huge number of complex synapse interconnections; and those connections also do double-duty as day-to-day processing elements . . . and the brain will freely reassign those depending on the priority of the moment.

I think that falls under "depending on the society in question." A socialist economy might actually have less trouble coping with the weirdness of the situation. Depending on the numbers of those younger generations, though, they could either be a marginalized minority or a vast, discontent majority. In the former case they're screwed; in the latter case they'll ultimately remake the system by weight of numbers unless you assume that the system is a perfect tyranny.

(1984 is a 'perfect' tyranny, for example, or at least Orwell portrayed it as one. Perfect tyrannies are the ones that can't be overthrown even in theory, except by Alien Space Bats coming in from outside the system. In real life, there arguably aren't any and hopefully can't be any).

Then again, socialism as we traditionally understand it might have trouble with this situation too. When you think about it, changing something about human nature as basic as "whether people die" should make a lot of human philosophy and political theory obsolete, so no surprises there.

I don't really think that any society can keep up an indefinite status quo that looks like:
1) Many people have no work
2) The people who do have work must work very hard to keep their job
3) You must work to live, or work to avoid misery.

This seems to me like it's going to be unstable by default- because almost every person in the system would be better off if the work were redistributed. The system may last a while, because there are plenty of other forces in play, but I doubt it could last for centuries. A system only persists when it makes most people in it feel like they're better off keeping it than they are changing it.

Except you don't completely lose skills - re-acquiring a "lost" skill is well known to be much, much easier than acquiring it in the first place. It does seem something of prior skills is retained. Likewise, a memory might pass beyond normal recall, but a stimulus might make recall easier. Old stuff isn't completely mapped away, at least not efficiently or quickly even if memories and skill erode over time.

As one ages memory does change. Children often remember exact details where adults don't. The mature human brain tends to not bother remembering details thought unimportant, only retaining those that seem important or interesting. As a child I might have remembered in exacting detail everything I ate for lunch the prior week, for example, but as an adult I don't bother, it's just not important. This might also account for phenomena where you drive somewhere and arrive, but don't remember the actual drive. Your brain is processing and functioning during the drive, but doesn't bother to remember it because the route is so routine and that trip so uneventful.

So, there is already a memory-saving feature of sorts. Assuming the biological immortality also comes with a lack of brain cell die-off or deterioration retaining a decent memory for a couple centuries might not be much of a problem.

When you start getting into thousands of years that might get problematic. I'm wondering if we might come up with a technological solution to that problem.