Cancer works by making cells split and reproduce at an accelerated rate, slowly and painfully killing the afflicted. Its true weapon lies in its ability to surpass the immunity system.

As far as I can tell, no matter how the cells of an alien work, there is no way to make them immune to this. So I must ask, is the basic premise of cancer universal? How can I design a species whose immunity system is immune to cancer?

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    $\begingroup$ I'd go with: "We have no idea at this point." I doubt there is an universal rule that requires every species to have cancer without external meddling, though, $\endgroup$ Commented Jun 28, 2016 at 18:26
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    $\begingroup$ Fun Fact: The naked mole rat has never been seen to develop tumors. Does this mean it's immune to cancer? It's impossible to prove a negative, so... Maybe? $\endgroup$
    – Frostfyre
    Commented Jun 28, 2016 at 19:07
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    $\begingroup$ Does an alien really have to be made out of cells? $\endgroup$
    – user2781
    Commented Jun 29, 2016 at 11:02
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    $\begingroup$ Single-celled organisms don't suffer from cancer. They enjoy the moments when they can pull it off. $\endgroup$ Commented Jun 29, 2016 at 17:39
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    $\begingroup$ There are reasons to believe that the answer is yes, it is universal. A living organism sustains damage as it ages, and it needs to self-repair. Self-repair involves propagating (copying) its own blueprint (DNA), and risking the introduction of errors which may lead to cancer. There is the idea that there is a fundamental tradeoff between longevity and cancer risk. No self-repair = die of old age. Too much repair = high risk of cancer. Similar ideas are discussed e.g. in this paper in a fairly general way (not specific to Earth-creatures). $\endgroup$
    – Szabolcs
    Commented Jul 1, 2016 at 13:05

16 Answers 16


Cancer is not a disease in the same way as, say, hepatitis. Every cancer is different - and not just e.g. skin cancer versus lung cancer, but really even John's lung cancer versus Peter's lung cancer. The only element all the various types of cancer have in common is that some cell in the body basically turns parasitic, and starts dividing uncontrollably, while tapping the body's resources.

Fundamentally, this is a result of the breakdown of the usual role the cell has. This is always a result of DNA damage - of course, the most famous source is from radiation (nuclear instruments, UV light, radioactive carbon and potassium etc.), but the reality is that each cell in your body is in a constant fight against deterioration, most notably from oxidative stress and infection. DNA is quite stable, but even the strongest bond can be broken if you "hit" it forcefully enough. However, there's a limit to how stable DNA can be, because evolution requires some kind of instability to introduce new variations in the genome.

And that's the real rub. You need something unstable enough to allow changes which are (extremely rarely) positive, and give you a better adaptation to your environment, as well as giving your species as a whole a better resistance to change). This is the same thing that gives you cancer.

Okay, you might think, why not make it so that change is possible in sexual cells, but not all the other cells in your body? There's two tricky points. One is that different cells use different portions of the whole code, and in fact, two cells of the same type may have different "effective" DNA, based on which of the two variants (one from mother, one from father) of the code is used in any particular cell. If this was visible, you'd appear striped - in fact, it's what causes striped colouring in calico cats. But the main point is even trickier - in most multi-cellular complex life on Earth, the same[1] mechanism is used for dividing sperm cells as every other cell. Even worse, the same main mechanism is used during usual cell operation, not just during division - all those proteins your cells make are first copied from the DNA, which needs to be partially "unwrapped" (which makes it more vulnerable).

Why not have a different mechanism? The fun part is, there have been different mechanisms in EarthLife's past (and they're still present in many organisms). It's just that DNA is the best we've got - evolution didn't stumble on anything better yet. Our cells are full of mechanisms to prevent cancer, and our bodies as a whole are as well. The problem is that there's so many cells, dividing (and dying) all the time - even with all the repair mechanisms, once in a while, a cell goes "rogue". Almost always, it's very quickly destroyed from the outside (or happens to starve etc.). Only when all the mechanisms fail do you get a tumour, and even then, it's not necessarily the "real bad cancer that kills you eventually" - most growths are not deadly. You need a growth that can "bleed your blood dry" of nutrients, or that interferes with normal functioning of the rest of your body (e.g. blocking blood passage, destroying surrounding tissue).

The same things that enable cancer are really the same things that are required for life to work (and evolve) in the first place. Even if it were physically possible to make a data structure that's impervious to all damage, you need to "damage" it in order for cells to divide, and possibly to read the data (that's the way it works with DNA). If it's hard to do that "damage", you will grow slower, and the changes in the populations will be rarer - in other words, some other thing, faster growing and/or more adaptable, is going to eat you or starve you. No repair mechanism can ever be perfect, because the damage can always occur in the repair mechanism itself. Our own bodies' repair systems are incredibly reliable (it's necessary for any large, long living multi-cellular organism), but they're applied very often. And of course, we're under pretty much constant attack by other organisms that seek to change our body processes for their own benefit (various parasites including viruses).

The best you can do is remove as many causes of damage as possible. For example:

  • The aliens live deep in the ocean, and are entirely shielded from most radiation.
  • There's no free oxygen (and other strong oxidants) in their environment.
  • There's no parasites smaller than your own cells, or parasites that overwrite your own genetic information (e.g. viruses); this is a bit tricky - you'd need something that reliably destroys small things without damaging bigger things.
  • The alien's body is resistant to systemic changes and localised damage. For example, cancer is quite common in plants, but it has no way to spread systemically, and damaging one part of the body rarely does significant damage to the whole. This can make some quite alien aliens indeed ;) If you take an ant colony as a single life-form, this is their strategy against cancer as well - cancer doesn't spread between individual ants, so unless it affects the queen, the colony survives.
  • The metabolic rates of everything on their world are much lower than ours. This basically gives the repair mechanisms more time to fix any problems before they grow too much. This is basically how chemotherapy works - it prevents all your cells from dividing (which causes the infamous "hair falling out" etc.), which hits the cancerous cells by far the most, since they divide "unrestricted" under normal circumstances.
  • There's a systemic repair mechanism ("genetic white cells/antigens") that continually identifies any deviations from "standard" genetic data, and marks the cells for termination. Of course, this would be extremely expensive and might cause you quite a bit of trouble if that's what gets broken - your marker would start marking every healthy cell for termination, ouch. It might be interesting for your story though - for one, it might be something humans might want to adapt to their own physiologies, and two, it might create a "cool disease" in the aliens that could be transferable to humans with disastrous effects. And with a repair mechanism like that, the aliens might lack one of the mechanisms that causes biological ageing - potentially making this whole thing even more attractive to humans, with promises of "immortality".

[1]: Okay, not exactly the same - but they have the same weak point, DNA replication and transcription. DNA is at the center, not the exact replication process - you need information storage strong enough to withstand environmental damage, but weak enough to allow replication and transcription.

  • $\begingroup$ Your 4th idea is exactly what I thought for my collective mind 'anthills' +1 $\endgroup$
    – TrEs-2b
    Commented Jun 29, 2016 at 21:16
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    $\begingroup$ "Okay, you might think, why not make it so that change is possible in sexual cells, but not all the other cells in your body?" Possibly worth thinking about the fact that ovarian cancer is known as being one of the worst kinds. If I recall correctly, it's known for spreading quickly and being extremely difficult to treat. $\endgroup$
    – jpmc26
    Commented Jun 30, 2016 at 23:04
  • $\begingroup$ @jpmc26 Yeah, your sex cells production cells churn out combinations of genetic material all the time, which means more chance for problematic crossover and mutation - each of your sperm cells is different, and they are less resistant to environmental factors (and yes, this does matter even for ovaries). The truth is, all of those strategies I mentioned are already present in humans, they just aren't apparent when you take us as the "cancerous base-line losers". We're not the best animal in resistance to cancer, but we're out there on the top. $\endgroup$
    – Luaan
    Commented Jul 1, 2016 at 8:08
  • $\begingroup$ I'd make the point against "in most multi-cellular complex life on Earth, the same mechanism is used for dividing sperm cells as every other cell". Mitosis is the process in normal cell division, while Meiosis is the process for the creation of sperm/egg cells. They're pretty different mechanisms, in actuality. $\endgroup$ Commented Jul 22, 2016 at 8:08
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    $\begingroup$ @user2979044 In the interest of pedantry, you are right. But they're close enough for my argument - they both depend on exactly the same kind of processes, except that the final result is four haploid cells instead of two diploid cells. Note how the weak point is DNA replication (and transcription), which necessarily occurs in both processes. $\endgroup$
    – Luaan
    Commented Jul 22, 2016 at 8:14

Cancer is typically caused by improper DNA repair. The gist of it is that cellular DNA becomes damaged in such a way that a repair to the DNA of the cell fails to restore the original DNA, and also corrupts it in such a way that other cellular mechanics to encourage programmed cell death under these circumstances do not trigger.

Now, the human body repairs a lot of damage to cellular DNA every day, and the odds of this kind of improper DNA repair happening, and it having the necessary changes in DNA to become cancerous, is fairly rare (otherwise everyone would have cancer from the day they were born). It is a statistics game, however, and unless something else kills us beforehand, statistically speaking, everyone will get cancer.

Cancer spreads rapidly by several mechanisms, but one of the key ones is the activation of Telomerase, a Ribonucleic Protein that add a telomere repeating pattern to the end of a DNA chain (typically these patterns naturally limit the number of times a cell can divide, the Telomerase removes this limit). Without a mechanism to limit the number of times a cell can divide, they divide indiscriminately and constantly.

Cancer tends to bypass the immune system because it is composed of cells from the same host, and is often recognized as part of the healthy body (one of the research pathways to cancer fighting drugs is aimed at flagging cancer as a foreign body).

In theory, a virus or other method could be devised to inflict a cancer-like disease on an alien race. However, depending on how their biology works, it may or may not have the same effect. They could be different enough on a biological level that they would be immune to cancers, and the condition would never occur.

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    $\begingroup$ If they are immune to cancer would that not imply a sort of biological immortality? $\endgroup$
    – James
    Commented Jun 28, 2016 at 18:50
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    $\begingroup$ @James it would not imply that. Among humans, if we were immune to cancer and had perfect DNA repair, we would still die from old age as cells stopped dividing when they reached the limits of their Telomeres. Cells die for a vast variety of reasons, and eventually something would fail in our bodies, it just wouldn't be cancerous $\endgroup$ Commented Jun 28, 2016 at 19:06
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    $\begingroup$ "the odds of this kind of improper DNA repair happening, and it having the necessary changes in DNA to become cancerous, is fairly rare (otherwise everyone would have cancer from the day they were born)." It's not just chance. The immune system does also repress tumor development over the course of our lives. 1 2 3 (If it was just a statistics game, many of us would die of cancer far earlier.) $\endgroup$ Commented Jun 29, 2016 at 0:43
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    $\begingroup$ @InstantMuffin at a rate of up to a million individual molecular lesions per cell per day, rare is relative. $\endgroup$ Commented Jun 29, 2016 at 13:06
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    $\begingroup$ It is important to realize that improper DNA repair is what gives rise to mutations, which is ultimately one of the main driving forces for genetic diversity over time. If a single celled organisms had perfect DNA repair they would never evolve because they would not be able to acquire new genetic information (unless there was another system, like viruses introducing DNA). So perfect DNA repair must be a late game development, otherwise the main "engine" for evolution wouldn't happen. You gotta have a lot of individuals die of cancer/genetic disease in order to get one beneficial mutation. $\endgroup$
    – Jason K
    Commented Jun 30, 2016 at 14:42

Cancer is evolution wrecking your life. That is, many of the cells in your body are capable of dividing and making more cells like themselves. Like full-fledged organisms, this division sometimes goes awry, producing mutant cells. Some mutant cells are are unaffected by the mutation. Some are unviable and die on their own. A few would thrive, but the immune system catches them and kills them. A smaller few thrive and are not caught by the immune system but reproduce at a modest rate, producing various minor benign tumours. Once in a while, a mutant arises that can evade the immune system and replicate aggressively. This is cancer. And once you have cells replicating aggressively, evolution kicks in: the ones that are better at dodging the immune system live longer and have more descendants. The ones that are better at dodging cancer treatments live longer and have more descendants. The ones that are better at spreading all over the body live longer and have more descendants, and may well kill you. A few are even able to attack other individuals (devil facial cancer, canine venereal cancer) or even other species (there's one in molluscs): cells from a multicellular organism have turned into a pathogen.

Really it's a miracle that cancers are as tractable as they are. Because they all start as minor modifications of the human genome, and because the immune system is pretty good, there are a relatively limited number of weak points where cancer frequently arises, which is why cancers often fall into recognizable types. That said, every cancer is different, particularly as they become advanced, because the population of mutant cells is evolving to resist everything thrown at it.

Could an organism be cancer-free? Well, I don't want to say too much about really wild ideas for organisms (energy structures, silicon life forms, informational organisms) but terrestrial organisms are mostly made from cells, which at their hearts want to be independent self-replicating organisms. But some kinds of human cell intentionally cannot replicate: red blood cells are the most obvious example, since they do not even have nuclei. The cells that make red blood cells, though, they can go bad. So an organism whose cells were all, or almost all, designed so they couldn't self-replicate would be quite resistant to cancer. But it's got to repair itself somehow, and if that repair mechanism goes wrong, it will damage the organism. It won't be a self-replicating kind of damage, but such a centralized repair mechanism would have to be capable of much more extensive repair on an organism whose pieces don't repair or replace themselves, so a broken repair mechanism could do much more damage. Single-celled organisms (some of which can be visible to the naked eye) are like this - they don't have any sub-parts capable of replicating themselves, but their repair mechanism is also completely centralized, and they mostly survive by spamming the environment with easily-killed copies of themselves.

I'd say that cancer or something like it seems likely in any organism that comes out of a process of evolution. Obviously organisms can be more or less vulnerable to it, but being less vulnerable to cancer probably also comes with being less adaptable (not to mention the risks of having a too-aggressive immune system - autoimmune effects produce all sorts of things from type I diabetes to arthritis).

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    $\begingroup$ Good answer. I feel your answer complements mine especially well (since my solution does exactly as you suggest and sacrifices adaptability and risks an over-aggressive immune system). $\endgroup$ Commented Jun 29, 2016 at 2:23
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    $\begingroup$ I also considered designing a creature where all cell division was concentrated into special "generative organs" (like meristems in plants), but I figured the consequences of a mutation occurring within such an organ would be too catastrophic. $\endgroup$ Commented Jun 29, 2016 at 2:28
  • $\begingroup$ The immune system plays next to no part in fighting cancer. If it did, then a compromised immune system would lead to more cancer, it doesn't. There is a strain of research mice called "naked mice" (no fur) which have no immune system. They don't get cancer at any higher rates. $\endgroup$
    – TechZen
    Commented Jun 29, 2016 at 20:22
  • $\begingroup$ Actually, one of the first things people noticed that led to the discovery of AIDS was the occurrence of Kaposi's sarcoma, an otherwise rare cancer that occurs only in immunocompromised individuals. Cancers that would normally be identified and killed by the immune system do indeed proliferate when the immune system isn't working right. $\endgroup$
    – Anne
    Commented Mar 15, 2017 at 13:51

I disagree with the accepted answer.

My Short Answer:

Any system that can evolve will be subject to cancer. Cancer is driven by the same entropy increasing mechanism that drives evolution itself. An evolving system does not have to be DNA based, RNA based or organic/living at all.

All that is required for a system to evolve is: 1) It must have pattern that reproduces or is reproduced, 2) the pattern must be mutable. 3) Given the right environment unit N must be able to produce the next generation with at least with at least N+1 units in the next generation. 3) The specific configuration of the pattern must be able to affect the rate of reproduction. 4) The mutated pattern must increase the overall entropy of the universe in order to persist.

This is why we can use genetic algorithms with oft times produce entire unexpected results i.e. an antenna controller "grown" with generic algorithms turned out to work only in one place, it's original location on the lab bench. Turned out, it evolved to used a part of a nearby piece of unrelated equipment to enhance its own antenna.

Entropy driven natural selection operates independently on multiple levels of the same organism. When it causes a subunit of a larger system to reproduce uncontrollably and to the detriment of the larger unit, we call that a cancer.

Just as natural selection is independent of pattern storage or reproduction mechanism, so is cancer. You will get cancer in a DNA based system, RNA or some other natural organic process e.g. prions, or technological systems both in hardware and software e.g. the grey ooze nanobots.

(I have an acquaintance who was using agent modeling for a simulated ecosystem. One agent mutated outside the set the bounds and it ate the rest of the ecosystem entirely. The robots will always rebel.)

Long Answer:

Evolution is driven by the increase in universal entropy generated during the creation of complex structures and systems. The easiest why to think about the phenomenon is to compare the lengthening of wavelength in a planets albedo (the ratio between the amount of light of specific wavelength striking a planet to the amount it radiates. Simplistically) The lengthening of wavelength means less work can be performed and thus the amount of entropy in the universe over all increases.

The creation of complex organic molecules, systems of such molecules, then living organism that constantly build complexity and while doing so, produce more entropy than say, a rock sitting on Mars.

(BTW: This is also the answer to creationist who say that adaptation in natural selection is tautological. It's not, only adaptation that produce more entropy than existing or competing structures will be selected.)

Life on earth is composed of nested levels of reproducing patterns or units each of which becomes a unit of selection i.e. a pattern upon which natural/entropic selection can operate on. Each larger level is the environment in which the subunits "compete". E.G. Almost all genes come in slightly different versions called alleles. Alleles compete with each other for the gene's position in the greater DNA structure, the loci. There is a form of gene cancer in which an allele inserts multiple copies of itself at its loci. Almost always fatal but its clear that some extant genes started out as "cancers".

All genes cooperate to create the cell, the greater environment in which the genes exist. Cells in turn cooperate to create organisms, organisms (especially sexually reproducing ones) cooperate to create strains and species.

Cells were the original organisms and multicellular organisms are collections of structures that once reproduced themselves to the maximum extent possible (which generates more entropy.) A tremendous amount of cellular mechanism exist which do nothing but control the reproduction of the cell. The vast majority of cells have all their reproduction switched off and most new cells are split off from stem cells. Most cancers arise from the failure of reproduction suppression in stem cells because stem cells have most of their safeguards switched off so they can produce new cells. They more easily revert freeform cell type that does nothing but reproduce. That's why its hard to permanently "cure" a cancer, you have to kill every single mutated stem cell.

It's easy to see how even self-reproducing technology will turn cancerous. Nanobots or evolving software will be just as affected by the 2nd law driving them to increase entropy, so eventually they will mutate to a form that will increase entropy by reproducing without regard to any larger systems.

If software can turn cancerous, then alien biologies will as well. It doesn't matter what they're composed of, as long as they can evolve, which they must to exist, then eventually, they will have units that will mutate into cancers.


Assuming the alien life form is multicellular, it should definitively know cancer. Cancer is basically a defect in the mechanism that controls the cell division. Cell division is absolutely essential for growth and reproduction. Also, the multicellular life will have evolved from single-cellular life, as that is the simpler one. Singe cell organisms divide as long as they have the resources, as that is the key to evolutionary success. Therefore the original program of a cell is to multiply uncontrolled; basically the cancer cell is the original.

The control mechanisms are then "bolted on" to enable multicellular organisms; however, any limitations have to be limited for gametes, or else the organism cannot multiply unlimited; a species that can only generate a limited number of progeny generations will die out. So evolution cannot simply destroy the mechanisms that allow unlimited cell division; it has to make sure that it is limited to be activated only when generating offspring, and then again deactivated in the offspring except when generating the next generation.

So any multicellular life will have cells which in principle can multiply without limit, but which have mechanisms to prevent that in most cells, so that cells only multiply in a controlled way when the organism needs it.

But whenever there's such a mechanism, it can be damaged by environmental influences (ionizing radiation — that one should be quite universal —, certain chemicals — which probably depend on the details of the biology —, possibly pathogens — likely organism specific —, and maybe other causes). And if the control mechanism is damaged in the right way, it should result in uncontrolled growth of cells. That is, cancer.

However note the one condition I've mentioned above: Multicellular. For example, a giant intelligent amoeba would not get cancer, simply because it has no cells that can get out of control. It only has one (giant) cell, that is itself, and cell division is just how that amoeba multiplies. Now of course that raises the question whether a giant intelligent amoeba would be possible, but it was just an example anyway. Any way to make those life forms not built out of individual cells would work.


I would use this interesting little guy for inspiration.


The important bit:

In its stationary phase, each bacterial cell contains four copies of this genome; when rapidly multiplying, each bacterium contains 8-10 copies of the genome.

This bacterium also has extreme DNA repair mechanisms. These same mechanisms which make it highly resistant to ionizing radiation would also theoretically help prevent a higher order species from getting cancer.


Any multi-cellular organism can get cancer. However, depending on how alien you're willing to go, it might be possible to devise an organism that is much less susceptible to its effects.

Plants, for instance, can get cancer, but are generally not harmed by it. Did you ever see a tree with a little burl or knot on it? That's a tumor. But since plants don't have localized organs or a structured body plan that can be disrupted by a tumor, it doesn't really do anything to their health. And since plants are rigid, the tumor doesn't metastasize like animal cancers do.

Anything amorphous, unstructured, or capable of full-body regeneration will not be especially bothered by a little piece of itself multiplying uncontrollably. As long as it isn't operating like an animal, you can probably find a way for cancer not to bother it.

Hive minds are another possible route - the individual animals can still get cancer, of course, but the death of any one of them won't affect the organism as a whole.

It is also possible that an animal species could naturally develop a more effective biological means of detecting and killing cancer, if resisting cancer was a major factor in its evolutionary fitness. The main reason why most species on Earth don't bother is because there's little reason to - the chances of being killed by something else is so much higher that cancer isn't really worth looking into, especially since the anti-cancer mechanisms might cause drawbacks in other, more important areas (being more careful with cell division might mean slower growth and healing, for instance). It's only in recent times, where we've dealt with most of the other things that can kill us, that cancer is even an issue, and evolution hasn't caught up yet.


Cancer is caused by mutations to critical parts of a cell's DNA causing it to reproduce at an uncontrolled rate. Usually multiple mutations must accumulate over successive cellular generations in order for a fully malignant tumor to develop.

Human cells are genetically "programmed" to correct mutations (DNA repair) and to kill themselves if their DNA is irreparably damaged. But if the cell's suicide or repair mechanism is itself broken by a mutation, then further mutations can occur, leading to cancer.

The immune system is tasked with killing things that it doesn't recognize as human. That's the problem with cancer that you pointed out: even if a cell mutates to rapidly reproduce and grow into harmful tumors, it will still usually register as human to an immune cell.

There's actually a really simple* solution to this problem: unify the DNA repair and cellular recognition pathways.

*(Actually unbelievably complicated, but "simple" in that there is a very simple underlying idea).

There are many ways this could be done: transcribe short portions of the genome that are important for DNA repair, transport them to the surface of the cell, and use them as recognition sites for the immune cells. If enough of them don't match, indicating a mutation in the genome, the immune cell destroys it.

Alternatively, the specific proteins and enzymes involved in DNA repair could themselves be moved to the surface of the cell and used as recognition sites. Maybe the immune cells could even present them with short fragments of DNA and see if they repair them correctly.

The details are impossible to flesh out mentally, but the general idea seems perfectly biologically plausible: Force the cells to constantly express that they are reproducing and repairing their DNA correctly, or else the immune cells explode them.

This wouldn't prevent mutations from occurring, but it would prevent them from accumulating. This should be enough to stop cancer from being a problem.

Technically, this scheme wouldn't categorically eliminate cancer, since there could always be a mutation in the immune cells that breaks the recognition mechanism--but now we're talking about highly specific complementary mutations occurring in unrelated cell types in different tissues on the body, and enough immune cells being affected to break the system. The odds of the necessary mutations occurring in both the potentially cancerous cell and in a majority of the body's immune cells is so low that it makes cancer as we know it virtually impossible.

Such a system would be remarkably unlikely to evolve on its own. A species that prevents mutations in its DNA won't be very good at evolving and will probably go extinct, so I imagine this mechanism would only appear after millions or billions of years of having a normally evolving immune system (the DNA repair mechanisms have to appear in the first place and evolve until they're good before they can be "locked in" as I'm describing). But I don't think it's too much of a stretch considering how outrageously complicated the human immune system already is. Don't expect such a system to be commonplace among alien races, but given an entire galaxy of potential and maybe a few billion years of an evolutionary head start, and I think it's believable.


I remember seeing a presentation on YouTube about cancer research. Cancer is not just uncontrolled reproduction. Sometimes you get such simple tumors, but they are not the really bothersome things. A tumor that calls for its own blood supply and later metastasizes is the real killer. I don't remember who, but the speaker pointed out several things that cancer does that's not simply malfunctioning, but is running the wrong program.

What if an alien (or nanotechnology) did not keep the whole program in all cells? Rather than deactivating parts and turning on others as cells differentiated, what if the daughter cell was only given the programs it needed for that role?

A mature liver cell would not be able to run subroutines meant for use in growing an embrio. It simply would not be available to be run!

An alien multi-cellular life form might be so different as to make the very concepts not apply, even though we think of them as assumptions and can't easily imagine otherwise.

On some previous answer, I showed an example of cells that have two nuculi and use different DNA for sexual and asexual reproduction. What if that became the basis of a multi-celled life form? Dividing within the body to keep renewing epithilial cells could use a different mechanism, and it only passes on the subset of DNA.


Cancer is universal, but not to biological life. As many answers have stated, cancer is a corruption to dna. However, dna does not define life. As a professor once stated when he was mentioning number theory's once infamousness for being useless, "dna is a form of encryption. It is basically a tiny von neumann architecture". If you did not understand what that means, here is it in very simple terms:

DNA is a form of programming. So, is cancer universal? Yes! The very device you are using proves it. For instance:

Hacker corrupts data in a program? That is cancer.

Random radiation switches a bit? That is cancer.

Program has a glitch that causes the computer to crash? That is cancer.

So... Can you make a species that is immune to cancer?

Alright, fine then. Create a race that is so alien and so otherwordly that their celullar structure does not function on any form of logic.


Or make up a completely blatantly ridiculous explanation as how cancer can be completely guarded against (complete subquark isolation barriers between cells might prevent anything from damaging to them, but then there is an issue of flat out immortality). Since anything with any force could manage to damage a cell (even a ridiculously well aimed punch might do it), your only option would be to devise a system of logic that is capable of preventing any corruption. Good luck.

Your solution essentially leans on the following:

devise an explanation for the existence of a program that if corrupted in some way, will either 100% repair itself or terminate.

I have to say, I really love this question.

  • $\begingroup$ While I don't entirely agree with the specific examples, +1 for the novel point of view. $\endgroup$
    – Peter
    Commented Jul 3, 2016 at 20:21
  • $\begingroup$ @Peter thank you. I actually know programming so from my point of view "cancer" is just a biological form of something much more broad. Of course, assuming that all variations are purely a corruption of DNA. $\endgroup$
    – user64742
    Commented Jul 3, 2016 at 20:22

Adding to the answers of @celtschk and @Anne: They both say that cancer is an inevitable consequence of having a multi-cellular organism.

One can imagine that other species have more cancer or less cancer than us, but they will have cancer.

Of course, as medical science gets better, we get better at detecting cancer in an early stage, and we also get better at curing cancer when we find it. We will probably soon reach the point where cancer no longer is a big deal, just a matter of seeing your doctor regularly.

Total immunity is probably impossible, but we could certainly be less cancer-prone than we are. Multiple redundant systems for mutation detection leading to repair or cell suicide would help. Actually, we already have that, but they aren't quite redundant enough.

The problem is that evolution leads to "planned obsolesce". As we age, we accumulate damage from all sorts of sources. From a evolutionary point of view, it is easier to just discard one generation when the next generation is ready, rather than putting lots of effort into repair systems.

Any species which is fresh out of their biological evolution era is likely to be in a similar situation.

As the species mature and starts modifying their own genome-equivalent, they can get away from this and become more robust. This will not only improve cancer defense but also delay aging in general.

Story idea: Write about the one single person on the planet dying from incurable cancer in some distant future. It would have to be somebody who have both skipped their medical controls AND have some complications that makes the cancer incurable. Scientists are working day and night to overcome these complications, but will they succeed in time?

Stray thought: A species whose global religion tell them that cancer is a sign of divine wrath, and who always kills the whole family of the diseased. This would give a strong evolutionary pressure to have strong cancer defense. Never totally immune, but far better than us.

  • $\begingroup$ "Soon". Give it like 150 years. Take a look at 5/10-year survival rates every ten years. Also keep in mind we're very very far away from understanding cancer. Chemotherapy just screws with cell growth in the entire body. Most antibodies we use inhibit blood vessel growth. We barely have anything that targets cancer cells specifically. And every cancer occurrence in every human body is unique. There will be a progressive increase in survival rate, some cancer types may get vaccines. But other than that: There is no one, singular cancer to get a cure for. A cure for cancers won't come "soon". $\endgroup$ Commented Jun 29, 2016 at 12:16
  • $\begingroup$ @InstantMuffin ah but don't be so pessimistic! You are thinking very traditional. What about mapping out an entire person's genome? That used to take years, now it takes minutes! That solves your unique problem. Now we have a good picture of what healthy DNA/cells should look like. Let's introduce some nanotechnology shall we? How about gene editing techniques, such as CISPR Editing? It's already been used to cure cancer! statnews.com/2015/11/05/… Imagine if we can generalize this! (Hint: we can) $\endgroup$
    – darethas
    Commented Jun 29, 2016 at 14:16
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    $\begingroup$ It is very naive to assume any progress on things we don't understand yet, just hoping someone will figure it out soon. I'm not thinking pessimistically or traditional at all. Do you know the trial process alone takes up to 20 years? Assuming of course funding doesn't get cut. Even if we find a(!) cure, how accessible will it be? And how much will it cost? Healthcare even here in Germany has a ton of issues getting people treated properly and in time. My mother has colon cancer and oncologists' offices are overflown with patients. No time to talk to them or even properly review their cases. $\endgroup$ Commented Jun 29, 2016 at 15:57
  • $\begingroup$ It basically looks like a slaughterhouse. So even if there is a singular cure (once again, cancer is not one singular disease), it won't be widely used in our lifetime, the healthcare systems of our most developed countries today will have a hard time supporting it, and the only reasonably assumption is to assume steady progress like it has been the last 40 years. No doctor or cancer researcher who doesn't try to say things to get funding will give you any other advice. $\endgroup$ Commented Jun 29, 2016 at 16:00
  • $\begingroup$ I have to admit my knowledge of cancer is based on popularized science. Sometimes very popularized. It seems there is an article every month about some new breakthrough against cancer. But I guess these articles aren't really to be trusted. $\endgroup$ Commented Jun 30, 2016 at 7:13

From a mathematical point of view, I would suggest that cancer is indeed universal. Seeing all the the cell processes together (in one life form) as a huge (programming) code, one could view cancer as a severe corruption of some lines in the code caused by error-inducing noise. Concretely, this 'noise' is just altering of the DNA by radiation, heat, etcetera.

Assuming that this noise is unavoidable, immunity for cancer means that the code of the life form is able to recognize (and recover) mistakes in his own code. This 'self reference' already gives an indication that such a code is not possible to exist.

As an example - there are some known parts of the life-form code that recognizes mistakes; proto-oncogenes regulate programmed cell-death (apoptosis). The main problem is that these genes can be corrupted too, which is indeed often the case in many forms of cancer.

There is even some mathematical proof that such a self-repairing code is not assumable to exist; it is called the 'Halting Problem'. Roughly translated to this context, it says that there is no program that can see whether some life-code goes on infinitely (see this as 'cancer') or halts eventually (see this as 'normal cell processes').


Elephants and Mole-Rats are both immune to cancer.

Their bodies evolved to kill or cannibalize cancer cells as soon as they find them.

But cancer is not a disease: it is an error in the mechanism of multi-cellular systems. All you have to do is make aliens that don't experience these errors or make them immune like elephants and rats on Earth...

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    $\begingroup$ Citation needed! $\endgroup$
    – JDługosz
    Commented Jun 30, 2016 at 2:13
  • $\begingroup$ citation needed for what ? $\endgroup$
    – user22162
    Commented Jun 30, 2016 at 10:44
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    $\begingroup$ That certain species are somehow immune to cancer. $\endgroup$
    – JDługosz
    Commented Jun 30, 2016 at 11:49
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    $\begingroup$ Elephants are not necessarily immune, but they certainly seem to be significantly more resistant than humans: nih.gov/news-events/nih-research-matters/… $\endgroup$ Commented Jun 30, 2016 at 15:04
  • $\begingroup$ Understanding how this substance, known as hyaluronan, protects naked mole rats from developing cancerous tumors could lead to novel cancer-prevention techniques for humans-Vera Gorbunova $\endgroup$
    – user22162
    Commented Jun 30, 2016 at 20:04

As cancer is caused by self-duplicating cells, you could easily create a creature that does not require any duplication of cells, thus being immune to cancer.

The drawback of no self-duplicating cells could be that once a cell is dead it wouldn't automatically be restored, if the alien race is synthesized and put together once without an internal self repair mechanism it would not develop cancer.

The immune system would probably have to be able to keep all existing cells alive instead of trying to kill cancerous reproductions.

  • $\begingroup$ How would such a creature be able to procreate? That might be better asked as a separate question, but since you are proposing the mechanism in this answer, it would be nice if you can give that (rather vital) part at least some attention in your answer. $\endgroup$
    – user
    Commented Jun 30, 2016 at 21:12
  • $\begingroup$ @MichaelKjörling, I was thinking the creature could be similar to a machine. We put together machines all the time, which typically don't have the ability to self repair. To reproduce, one could just synthesize a new creature from some sort of creature factory. There would be the question of where the creature factory comes from, but it could be turtles all the way down. $\endgroup$ Commented Jul 1, 2016 at 17:47
  • $\begingroup$ Actually, one of the main theories for why aging exists is because of this. Our cells have biological limits placed on how many times they can reproduce in order to make us less likely to get cancer, which means our bodies break down when we get old instead. We only get cancer when the system limiting cellular reproduction breaks. $\endgroup$ Commented Jul 3, 2016 at 7:09

My answer will serve as a complement to the user TechZen:

His reasoning that "the larger the biological system, the greater the degree of entropy it has to deal with, for example, the more cells an organism has, the more chance it has of suffering a genetic error that leads to cancer. So the maximum proportion that an organism can take is related to the maximum degree of entropy it can "fight"" was the reasoning that science for a long time had, taking the example of cancer: the more cells an organism has, the greater the chance of him getting cancer, after all, the more cells you have, the more genetic material you have and the more genetic operations you carry out

We find that large organisms like elephants, giraffes, and the blue whale (which is the largest organism that has ever existed in the entire history of life on the planet) simply have a ridiculously low cancer rate. To give you an idea, to this day not a single blue whale has been found with cancer. This contradiction is called the Peto Paradox. There are two hypotheses that try to explain why blue whales do not develop cancer: the first is that they have a sophisticated biochemical mechanism that is much more efficient than ours in correcting genetic problems. And the second is the hypercancer hypothesis, I'll send you more about it below

From humans to hydra: patterns of cancer across the tree of life - Albuquerque - 2018 - Biological Reviews - Wiley Online Library https://onlinelibrary.wiley.com/doi/full/10.1111/brv.12415

Massive animals may hold secrets of cancer suppression | Nature https://www.nature.com/articles/nature.2013.12258

(Here begins the first hypothesis as to why blue whales do not develop cancer, the rest was an introduction)

Peto’s Paradox: Evolution’s Prescription for Cancer Prevention https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3060950/

(Here about the second and craziest hypothesis: hypercancer)

Why don't all whales have cancer? A novel hypothesis resolving Peto's paradox | Integrative and Comparative Biology | Oxford Academic https://academic.oup.com/icb/article/47/2/317/719209#12636921

Oh, and another thing, rats have a cancer rate basically identical to ours, and they're much lower


Cancer is when the mechanism that controls the division of cells fails, causing cells to rapidly divide. I do not know of any earth creatures that are immune to cancer, although there are some that almost never get cancer. One example is the axolotl. This weird salamander can regenerate his limbs, and almost never gets cancer, and has actually been looked into as a potential way to develop a cure for cancer.

Even if your aliens aren't immune to cancer, they can be nearly so.


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