Ignorance is curable, living is forever. Robert A. Heinlein1

Cutting to the hard data:

Due to some or another reason2 the genetic information stored inside cells (aka DNA) of my Immortals does not deteriorate over time. Replacing old cells with new cells does not result in inferior/misaligned copies of the contained genetic code, thus cells can be renewed indefinitely.

The genetic code of any born Immortal can also not be altered by influence of radiation thus during the lifespan of an Immortal their cells will not mutate and thus will not get cancerous.
Now the cells of any unborn Immortal may still produce mutations and thus the species will further evolve more or less unhindered.

Q: Considering the above stated rules, What diseases will still be able to bring death to an Immortal, and Why?

1Well mostly at least
2Call it magic if that helps you

  • 3
    $\begingroup$ @Zxyrra I thought my writing made it pretty clear but here I go: The genetic information stored in their cells does not deteriorate over time, thus they do not age as we call it. There is nothing that precludes stabbing them to death or similar things, as there is no mention of increased metabolism or super-fast-cell-duplication $\endgroup$
    – dot_Sp0T
    Dec 2, 2016 at 12:19
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    $\begingroup$ Why need magic, you just need a really good proof-reading polymerase :) And some mechanism to stop telomeres shortening... $\endgroup$
    – user29657
    Dec 2, 2016 at 12:19
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    $\begingroup$ If anything your immortals will quickly become MORE vulnerable to disease, since they can't mutate anymore. Quickly on a evolutionary scale anyway. $\endgroup$
    – John
    Dec 2, 2016 at 14:42
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    $\begingroup$ Steel poisoning to the neck applied with force. I submit they they will slowly die off, since There Can Only Be One. $\endgroup$
    – PhasedOut
    Dec 2, 2016 at 16:11
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    $\begingroup$ @dot_Sp0T: There is really no proof that genetic deteoriation has anything to do with aging, and some logical reasons to think it might not. For instance, if it did then all organisms ought to have similar lifespans. $\endgroup$
    – jamesqf
    Dec 2, 2016 at 18:12

8 Answers 8


Anything that isn't cancer.

You seem to describe something known as biological immortality, which occurs when an organism cannot simply die of old age. Lucky, a jellyfish species called Turritopsis dohrnii has this condition. Let's talk about what kills them.

Even if death from old age cannot occur, microbes can kill the body. Viruses may be out of the question if you're hard-set on the "no changing genetic code" aspect, but that still leaves bacteria, prions, and a host of other microorganisms - all capable of releasing deadly toxins, or overwhelming the immune system.

The ability to stay alive does not mean the inability to be killed. Predators of this species can still kill them, or, if they have no predators, then other members of the species can do it.

Additionally, consider

War Simple enough. Shooting, or stabbing, or bludgeoning, or lasering should do the trick.

Physical Conditions Things like heart attacks and strokes resulting from random chance or natural causes can kill this species.

Extreme temperatures, pressures, and other conditions should work.

In short, you've said "they're immune to cancer, but what else can kill them?" to which the answer is "anything but cancer"

  • 40
    $\begingroup$ Q: "What else can kill them?" A: "Yes" $\endgroup$
    – Erik
    Dec 2, 2016 at 13:24
  • $\begingroup$ If viruses are exempted, then OP's immortals are just immune against cancer caused by radiation, oxidative stress and maybe carcinogens. $\endgroup$
    – MauganRa
    Dec 2, 2016 at 15:15
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    $\begingroup$ @Erik Q: What else can kill them? A: everything else that kills normal people other than old age and cancer. $\endgroup$
    – Mindwin
    Dec 2, 2016 at 15:57
  • $\begingroup$ While accidental genetic alteration may not happen (radiation, etc) what about deliberate manipulation and/or insertion? $\endgroup$
    – nijineko
    Dec 2, 2016 at 17:41
  • $\begingroup$ @nijineko that's possible although maybe not as likely $\endgroup$
    – Zxyrra
    Dec 2, 2016 at 20:23

If you discount every single acute event, like infections and traumas (and for which there are good treatments nowadays), I would say that the diseases that would affect your immortals the most would be degenerative diseases, like dementia, amiloidosis and vascular diseases.

Even if the DNA doesn't suffer damage, the natural entropy of the continuous functioning of the organism will produce deterioration.

The bones will deteriorate so much that the immortal will eventually suffer from severe osteoarthrosis, rendering your immortal unable to move.

The neurons will also deteriorate eventually and lead to dementia.

Debris from the constant metabolism will eventually accumulate on the organs, inhibiting their normal functioning through mechanisms of amiloydosis

Also, even if the immortal has perfect sugar or lipid control, eventually the blood vessels will be coated with hidrophobic fat, leading to atherosclerotic events. Sugar or other molecular radicals will bond the natural molecules of the blood vessel wall and produce damage. Lastly, blood vessels will calcify or rupture from shear continuous usage.

The blood vessels and the heart will also undergo processes of remodeling to acomodate to continuous blood flow, loosening their elastic properties. These processes will lessen the efficacy of the heart, or produce aneurisms... which could lead to fatal hemorrhages or cardiovascular events if the immortal is allocated to a situation of physical or psychological stress.

Just like the blood vessels may be blocked by atherosclerosis, the bile will cristalize in the gallbladder and these crystals will block the biliary ducts, which could lead to fatal cholangitis and cholecystitis

Please note that these disorders will occur even in the absence of genetic damage, but the body will be unable to repair these lesions (at least if we're talking about a human body that is similar to our own, except for the DNA repair mechanisms). Old people without cancer die from these disorders. Machines, that by definition, don't have genes, cease to be able to operate after some years due to simple overusage.

In short, the body will exhaust itself from the continuous functioning in the long run and the immortal will suffer from every kind of degenerative disease.


What about DNA changes from other causes than misreplication or radiation?

Viruses can affect the reproduction of DNA. For example, the Tasmanian Devil was almost wiped out by a contagious form of face cancer, and the HPV virus causes cervical cancer.

Then there are causes of death that don't involve the DNA. This will depend on the mechanism for immortality.

Parasites can cause death - even the humble tapeworm, untreated, can cause cysts in the brain and heart.

Magnesium deficiency can lead to heart attack.

Bacteria and funguses that produce neurotoxins.

Extremely high fever. Anaphylactic shock.

And so on - unless your immortality device takes care of any and all parasites, bacteria, viruses, malnutrition, allergies, etc, etc, etc.

  • $\begingroup$ Tuberculosis is a perfect example (if the immune system can't handle it). $\endgroup$
    – Lu22
    Dec 2, 2016 at 12:20

Given time, theoretically only physical damage (stabbing, drowning, shooting, etc) should kill an immortal race.

Why? Because every other disease such as viral infections, bacteria, or lifestyle illnesses (diabetes, heart disease, osteoarthritis, etc) should, eventually, be selected against through targeted reproduction. Assuming your immortal race starts with the ENTIRE current earth population (i.e. we give everyone an inoculation that turns them and their kids immortal from there on out) then freezing DNA effectively halts mutation driven evolution. Your race is now static. BUT it can still adapt by mixing chromosomes via reproduction.

So HIV is a problem. But presumably a small subset of the population is immune to HIV because of their particular DNA/immune system (the part of the immune system driven by DNA rather than environmental factors). So, over time, these individuals will be selected for as HIV kills off other immortals (or, more likely, immortals selectively mate in order to increase the incidence of HIV immunity in their offspring). So now all the remaining immortals are immune to HIV. Rinse and repeat this for all other infectious organisms, lifestyle diseases, and even inherited diseases such as Huntingtons. An immortal population presumably would take a very long view on survivability and would actively cull out their weaknesses.

Now this would take a long time and would probably never be entirely successful. There may not be genetic immunities to every disease and this immortal race, unless they also have genetic engineering, can't develop any new genes through mutation. So they will start to slowly collapse towards a homogenous pool of genes and may lose important ones accidentally when culling out another gene on the same chromosome. Diseases will also continue to evolve and mutate, finding ways around the immortals immune system and as the immortals become more homogenous they are at greater risk of one disease striking them all down since they are unable to develop random mutations that might protect at least some individuals (we routinely lose entire monocrops to disease in this fashion).

But of course traditional medications, vaccines, antibiotics, and anti-virals will continue to be developed, with the benefit of not having to worry about the teratogenic side effects that cause so many problems with other drugs. So we may end up with a population immune to many diseases (which will then be eradicated if humans are the only reservoir) that also have to take a crap ton of vaccines and antibiotics to stop the spread of diseases they can not long develop any genetic immunity against unless they can also gene engineer themselves.

  • $\begingroup$ So evolution by mutation & selection would just slow down a loot. Kudos for bringing up how longevity can impair a species' adaptability if "cycle times" are not shorted by genetic engineering. $\endgroup$
    – MauganRa
    Dec 2, 2016 at 15:19

Zxyrra brings up a very good point. Your immortals have incorruptible DNA, but the rest of them is still left vulnerable.

If however, you go on to posit the rest of their physiology is equally incorruptible, my only thought is that perhaps only the physiology itself could kill itself:

Autoimmune Disease

Maybe if the immune system is more immortal than the rest of the body, it could kill the person if it turned on them and attacked them, in autoimmune fashion. The DNA may be incorruptible, but if the rest of the body gets annihilated by an overzealous immune system, it could result in death.

(P.S.: Harvard scientists already have immortal mice because the mice telomeres have been fixed. Maybe that is what you were referring to?)


Have no rep to add comment, but my guess is Mental Disease, if topic starter is open to this idea.

I think deep depression dive can easily kill what-ever immune bio-immortal dude in matter of centuries.

I can continue this list further, but you got the idea. Dont call it one-liner. It has more sense than over9000liner.

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    $\begingroup$ again, downvotes without reasoning! Very polite $\endgroup$
    – Sanctus
    Dec 4, 2016 at 1:30

Any disease that affects gut flora.

Immortal race must have immortal symbiotic microflora, or at least the other ways to digest their food (possible - intravenous feeding).

With gut flora being damaged by radiation, or by other bacteria/virus disease, the immortal will simply starve to death.

Thinking of symbiotic relationship: any disease capable of wiping most of livestock/other protein sources up to extinction would also be fatal for some of immortals.


Mental Diseases

Sadness: because all other died.

Bipolar Disorder: The manga "3x3 Eyes" they have a plot where the life need ups and downs, but like a drug the need for excitement always grow, not meeting the joy need, the immortals fall in depression or go insane trying to feed the never satiated need for joy.

Hungry: Ever-growing population causes food shortages

Parasites: A mutating parasite that fight the immortals evolution taking over the body little by little.


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