Disclaimer: I'm not a biologist or geneticist, so my knowledge on the following topics is limited. Feel free to point out any mistakes, but please be polite about it.

I'm currently planning a story where the entire human population is biologically immortal (meaning they can be killed, but they won't age after reaching adulthood or die of natural causes).

Here is my desired outcome / the conditions of the aforementioned immortality:

  • Humans don't age anymore, so they won't die of old age (Edit: If necessary, replace 'eternal life' with 'very long life (1k+ years)'; thanks @CortAmmon)
  • Cancer isn't a problem anymore (nobody gets cancer or cancerous/tumorous cells are automatically killed off by bodily functions or defective tissue can be cut out and the body will replace the missing parts with new, healthy tissue (see the regeneration capabilities below))
  • Other diseases can still occur and restrain or incapacitate people for some time, but eventually the body will fight off any disease, even those that aren't curable to our current knowledge (like HIV/AIDS).
  • The human body has increased regeneration capabilities, meaning wounds (even grave ones, such as a bullet in the head) will heal automatically to a certain extent, severed limbs will grow back (not within a day, but within a couple of years or decades (so no Resident Evil-level BS)). Therefore, the only way to kill/die permanently would be to destroy the body completely, e.g. burn it.
    • Edit: It's fine (even preferred, to be honest) if severe brain damage results in memory loss and the victim might have to relearn basic stuff or is basically setback to infancy. Thanks @Samuel for pointing that out!
  • To sum this up, any human can live eternally unless their body is permanently destroyed. Let's call people who meet these requirements 'super humans' for the sake of this question.

  • OPTIONAL: Super humans can survive for a long or even unlimited amount of time without nourishment. I tend to think this is entirely impossible, so it's not a requirement.

These conditions must be inheritable, meaning if two super humans (or a super human and a normal human) have a child (which by the way is in no way limited, so super humans can have an infinite amount of children in an infinite amount of time, while pregnancies still take the usual ~9 months), this child will also be a super human.

Even though this is basically science-fiction at the moment, I want the means by which this is achieved to be plausible (or as plausible as possible) with what we currently know about the human body. So I'm thinking genome manipulation, for example introducing a dominant allele into the human genome which will allow the human's cells to produce telomerase which in turn can regenerate telomeres so cell division won't be limited. I know this raises other problems such as increased cancer risk over time, but it's fine with me to assume those can be solved via more gene manipulation, so that in the end there will be one set of (manufactured) genes that can be implanted in selected individuals to create a super human. It doesn't matter if those selected individuals will become super humans as well, the only thing that matters is that their children (and all their descendants) will be super humans

So, my question is: Is this scenario plausible (given our current, limited knowledge)? Monetary ressources and time aren't an issue.

If so: How would the super humans most likely be created? Would the manipulated gene be surgically implanted in fetuses, or in sperm, or in the mother's egg cells prior to impregnation? Or is there another method that I'm not aware of (as long as the 'super-humanism' is inheritable, I'm fine with an approach that doesn't involve gene manipulation)? And can the optional requirement stated above be achieved that way as well?
If not: Can I make any assumptions about future discoveries/inventions which would make it possible? Or which of the requirements stated above would I have to drop to make it possible? (The one I'd be the least reluctant to drop are the regeneration capabilities, in case that matters)

Bonus points if you can tell me what timeframe to assume for both the discovery/invention of the required genes and methods and the replacement of humanity by 'super-humanity'.

  • 2
    $\begingroup$ I think some of your points could be done, but the handling of random mutations in genetics would be hard. At the cellular level, the world is actually quite a brutal place! Would you accept humans living for a long time, instead? Perhaps a thousand years? Too much further than that, and we might need to have a discussion as to what it means to be human, because the result might not actually be recognizable to you or I. $\endgroup$
    – Cort Ammon
    Oct 30, 2015 at 20:07
  • 1
    $\begingroup$ DNA isn't going to direct the re-growth of brain matter that contains the memory of where you put your keys last. Presumably a bullet to the head would destroy the information stored in the arrangement of the brain matter there, right? Otherwise all that information will need to be duplicated somewhere. $\endgroup$
    – Samuel
    Oct 30, 2015 at 20:11
  • $\begingroup$ @CortAmmon Good point, thanks! Actually, that's hard to answer. I'm planning a story about overpopulation caused by exponential population growth; I suppose a life expectancy of a thousand years would be more than enough for that to be plausible. However, I also wanted to include the pessimistic view on life and the eventual death-wish which (according to other stories on that topic) comes with an unlimited life-span. But I'd be happy with an answer that assume a highly prolonged life span instead of immortality. I'll have to make a few assumptions any way, so I guess that won't be a problem. $\endgroup$
    – MoritzLost
    Oct 30, 2015 at 20:16
  • $\begingroup$ Your people will need to be somehow immune against natural radiations, so their cells won't mutate as they age. Either that, or you blot out the sun and deplete all radioactive material from the Earth; not sure if either would be a good idea, though. $\endgroup$
    – Nolonar
    Oct 30, 2015 at 20:17
  • 1
    $\begingroup$ Well, our mechanism to detect mutations and fix them is really good, but not perfect. We've reached this state after millions of years of evolution. I suppose we could further improve on that mechanism through technology, but genetically manipulating all humans is going to be a bit difficult. But yes, it should be possible in theory. $\endgroup$
    – Nolonar
    Oct 30, 2015 at 20:34

4 Answers 4


There's a few problems to be explored, each with different solutions.

Cancer is a nasty one. The reason our cells do not all upregulate telemerase so we can live forever is because we'd rather give up that immortality to ensure cancer cells can't live forever. Remember, cancer cells are not "defective" because, like every cell in the body, it only has a purpose because human scientists have made the claim that it has a purpose. If you really look at how the body works, each cell does what it does, because it wants to, and it does it well.

You would have to come up with a more creative limiting process for cell growth. Perhaps a limit in reproduction rate, instead of number of reproductions, combined with a yet-undiscovered immune system boost which is constantly watching out for cells that are not "doing their job," like the KGB sniffing telephone conversations and steaming envelopes. (There's a recursion problem here, who watches the watchmen, but we'll get to that later). Put these together, and you don't need to downregulate telemerase anymore.

Regeneration is tricky because the physics of regeneration is brutally difficult. The body does not have before-and-after snapshots of the body, so it doesn't actually know what its trying to repair towards. Instead, its approach is to simply do the best with what it can. Regenerating small things, like skin cells, would be way easier than stitching a damaged neuron back through the spinal column. There's some precedent for such healing with other species, such as starfish and some amphibians. The tradeoff is easy: proper healing can take a very long time, while scarring can get you up and running quickly. Accordingly, these humans would need a great deal of time to recuperate after a bad injury, in which they may be far less capable than you or I during that time, because their repair system has had to place more demands on the body than ours do.

Now, for the feature which makes such a story just possible enough to take flight: society. These are not your average geckos, sharks, or other animal. These are humans, capable of building societies and developing the world to suit their needs. A society can do regeneration and healing that is not available to an individual. A society can develop machines which scan for cancer at a genetic level more precisely than could have been accomplished if the machines were coded into our DNA. A society can help regenerate limbs by creating the essential scaffolding needed to build the right cells at the right places. A society can even deal with the issues of radiation, by creating a culture where everybody covers up, all the time. A society can turn an individual that might live to be 200 into one that can live to be 2000!

A society can be a dark thing as well. A society can spend hundreds of years indoctrinating its individuals that the only purpose in life is immortality (see Nietzsche's Thus Spoke Zathrua). In fact, such insidious activities could even be applied as a side effect of having society help rebuild your memories after the inevitable brain injury. A society can structure itself to extend the immortality of a few individuals by crafting society around them to support the slowly growing weaknesses of those individuals. A society can build the dark oppression that leads to death-wishes.

And worse, society can build the oppression that prevents one from carrying out those wishes. You see, the ultimate immortality would not be found in a corporeal form. There's simply too much entropy involved. An ultimate being would be more distilled, freed from the limitations of the flesh. It might exist as an idea, shared within a society. Something which could be reincarnated into a body at any time by the clergy.

Such an entity would have to sustain itself, as it clearly can no longer eat. It could sustain itself on the energy of those to whom it has spread, checksumming its less reliable bits to ensure they are uncorrupted. This would require a common thought so that it could move freely amongst society. The stronger the thought is, the more ability it would have to act. This includes preventing others from acting on their death wish, for if they acted on it, it would no longer be immortal. Strong thoughts can move cultures.

"Who wants to live forever?" -Dune

  • $\begingroup$ Thanks for the elaborate answer! Also, +1 for including the thoughts on what a society built around immortality would entail. This actually gave me some interesting ideas ... Nietzsche is too heavy for me, but I'll definitely read a summary or something. Funny that you brought up entropy, as this is one thing that's always bugging me when I read something about 'immortality'. I like the scenario in 'The Last Question' by Isaac Asimov where even the non-corporeal hive-mind (close to the one you described) is eradicated by the Heat Death at maximum entropy (even though 'AC' isn't ... intesting.) $\endgroup$
    – MoritzLost
    Oct 30, 2015 at 21:12
  • $\begingroup$ @MoritzLost Happy to help. I mentioned Nietzsche because, that book, his description of The Last Man is really the heart of the society I depicted in the answer. I also love "The Last Question," though I particularly enjoy arguing that perhaps the AC isn't eradicated, just transformed. The beautiful last line of the story (which I wont spoil here in case others haven't read the story) leaves a lot to ponder =) $\endgroup$
    – Cort Ammon
    Oct 30, 2015 at 21:15
  • $\begingroup$ IIRC, AC and the human hive-mind are two seperate entities of which the latter is eradicated whereas AC continues to exist ... ? At least that was my understanding when I read it. Yeah that last line was really ... interesting. Even more so if we combine that with Nietzsche (even though God's death is more rhetorical in this case) ... well, I'm out of my element °v° $\endgroup$
    – MoritzLost
    Oct 30, 2015 at 21:21
  • $\begingroup$ Two questions regarding your answer: 1. at some point you wrote about extending the immortality of 'a few individuals' - is that compatible with my desired outcome where everyone is immortal / has a heavily increased life span? 2. What do you mean by 'covering up all the time' to prevent radiation? Would there be huge isolated facilities, lacking sun-light and nature? Or would everyone have to wear like a protective body-suit 24/7? Sorry, I know this is like a huge question on it's own ... $\endgroup$
    – MoritzLost
    Oct 30, 2015 at 21:34
  • 1
    $\begingroup$ As for the first question, you could extend the lifespans of every individual, but unequally. Perhaps most individuals could have theoretically lived to 500, but in the actual society, most live to 499 while a few live to several thousand years old. I use that wording because you can beat it into something that is thermodynamically atainable while at least one individual's mortality cannot be proven, without breaking any actual laws. 2) I think the level of pathology regarding protection from radiation is up to you. In the extreme, it'd be the 24/7 body suit, but that might not... $\endgroup$
    – Cort Ammon
    Oct 30, 2015 at 21:43

Well, we should look for the answer for this in biology bodies already present on earth.Trees have the capability to live for hundreds, if not thousands of years. This has been thought to be because plants use a different form of producing energy than animals. But photosynthesis does not produce enough energy to run the human body.

So, why does respiration make us live for such a shorter time than photosynthesis?

This is not actually that surprising considering that animal respiration is basically the same processes as combustion except replacing heat with an enzyme. It is an extremely destructive process compared to photosynthesis, resulting in the production of atoms termed free radicals that can harm the cells in the body.

It has been a theory that free radicals damage to our cells are a large cause of aging, as well as playing a major hand in other diseases such as cancer and other disease that become common with age.

So, if you reduce/remove the damage that these atoms cause. Then I believe it is likely to significantly improve the human life span.


If a person is defined as just a particular DNA sequence, then yeah, they can live forever.

I'd say you can make a human that lives forever, but probably not a person. However, if we consider a person who has had their entire brain destroyed then regrown from scratch (someone who has essentially reverted to infancy) as still the same person. Then really what difference is there between this and growing a clone, from an infant, of that person? I'd argue there is none.

These Super Humans (or perhaps Theseus Humans?) could "survive" anything as long as society regrew them from stored DNA. This is theoretically possible. To consider them the same person does require that slight modification in what many people might consider the definition of a person.

The other cheat... err, redefinition, is with inheritability. If we can consider that the offspring inherits not only the genes but also the society and infrastructure of their parents then all the desired abilities are inheritable. The ability to regrow a lost brain in a human will always require some external technology or intervention by society. That trait is only inheritable to the young who inherit that technology and/or society.

With those cheats in place, the rest is entirely plausible. Aside from regrowing a human when they're all but completely destroyed, our medical technology is already on track to implement the other desired features of these Theseus Humans.

People will mature, but not age. They won't get or keep cancer. Diseases will be eliminated. Improved regeneration through human enhancement of biology or technology will be a norm. Starvation might be prevented through technological means.

And we are going to have one hell of an existential crisis when we can choose not to die.

  • $\begingroup$ Thanks for the great answer! I didn't even consider this implication of my super humans ... or Theseus Humans, I like that. The existential crisis is an intesting topic to explore as well, reminds me of the personal identity problems laid out in thought experiments like the teleportation problem (I'm referring to 'The Pig that wants to be eaten'). Good thing you pointed out the difference between a human and a person, I'll remember not to use those terms synonymous in the future °v° $\endgroup$
    – MoritzLost
    Oct 30, 2015 at 21:34
  • $\begingroup$ Screening will still be especially important. Even living forever, unchecked metastatic cancer could require enough rebuilding that the personality may be fundamentally altered or lost. $\endgroup$
    – user8827
    Oct 31, 2015 at 7:17

Yes with enough genetic engineering you could make biologically immortal humans, but you will still need a strong medical infrastructure in the society. we age because there is not enough evolutionary advantage to not aging, we could engineer around that.Age is the easiest to fix since there already animals that do not age. echinoderms and possibly fish.

Cancer could be reduced to something like minor inconvenience, "damn it I have to go get a cancer removed, there goes my day" especially if you can use broad strokes cutting it out. the few people occasionally born with a mutation hampering this could go through gene therapy while they are young.

they only thing that will be problematic is the regeneration, limbs sure, lizards already can do that, and mice can do it in laboratory settings. the main reason we can't regrow limbs is we form scar tissue, which plugs the leak faster at the price of preventing regeneration. However repairing vital organs that are damaged to the point they no longer function is only going to happen with severe medical support to replace they organ or replace its function until it repairs itself. So only if you get them to a hospital fast enough. And damage to the brain is always going to be a problem, as a bad movie put it, "his brain tissue might grow back but his memories won't" unless your people have a way of creating a daily back scan of their brain, and then go through the surgical intensive process of making the regenerated brain match the scan.

your other problem that will develop is that your population will be very similar genetically and disease will be a bigger risk. No amount of genetic engineering will make you completely immune to disease, and when one does find a way around the improvements it will hit hard, and it will be medical technology that beats it not the body.

you also create new problems, they had better reduce the sex drive and fecundity while they are at it or the population will explode. especially since your death rate will be only dozens or hundreds of deaths out of billions people each year, assuming no wars.


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