I want a creature to be able to set itself on fire when in danger, but I need a way to protect tendons and heat sensitive organs like the brain and kidneys.

I'd imagine this creature to have a perfect insulation method evolved after millennia of heat stress caused by wild fires and eventually it evolved a mechanism to set itself on fire and exploit its own resistances. Now to burn, it needs fuel and fat tissue is the best around, so good in fact people used it for centuries to make explosives.

The immolation mechanism would be kind of like a lizard losing its own tail on purpose, but more extreme. Now there's a problem, cancers.

Cancers are not a chance, they are a certainty, if an animal regenerates fast enough and lives long enough it is implausible to not see a few cancers. When we also add smoke, we have a recipe for disaster.

Can cancers be isolated on the regenerated part? Imagine that animal having to rebuilt its skin once or twice a year... Many cancers are to be expected, but if the cancer remains isolated on the skin, then burning it off won't be a problem... If it spreads then the animal won't live much.

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    $\begingroup$ "Even for humans fire is only deadly either from kidneys collapsing, smoke suffocation and the brain boiling inside the skull." I don't think so... Burns can kill in a variety of ways. A third degree burn on a limb for example could cause compartment syndrome, which kills through gangrenes. But other than that, this is a VERY good question. It has been some time since I last saw a question that I like so much! $\endgroup$ Commented Jan 7, 2021 at 15:19
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    $\begingroup$ If your creature is large enough, they might be impervious to cancer through a mechanism called Peto's Paradox. Granted, usually being large is a defense in itself so you wouldn't need a self immolation mechanism... unless there's a predator even bigger (think era of the dinosaurs). Here's a video explaining the concept in more detail: youtu.be/1AElONvi9WQ $\endgroup$
    – Drake P
    Commented Jan 7, 2021 at 16:44
  • $\begingroup$ I edited out the bit about burns in humans. Check out the Rule of Nines and the rather unfavourable mortality rates of extensive burn injuries. Otherwise, great question! $\endgroup$
    – elemtilas
    Commented Jan 7, 2021 at 17:55
  • $\begingroup$ What is the meaning of the word "skin" in this question? If you mean only the epidermis, then many animals, including humans, already do rebuild it continuously. If you mean both the epidermis and the dermis, then I'm afraid there is no way to burn it off without destroying the underlying muscles, bones and blood vessels. $\endgroup$
    – AlexP
    Commented Jan 7, 2021 at 18:09
  • $\begingroup$ @AlexP I don't know man, I have a few scars as old as myself and some skin marks which stayed with me for the last 5 years, if our skin is rebuilt continuously it does so at an incredibly slow rate.... Even a simple skin scratch takes me one month and a half to heal completely, replacing all my skin in one year would be something else, for one I wouldn't have the same pimple on my face for over 5 weeks now... $\endgroup$
    – user81643
    Commented Jan 7, 2021 at 18:34

1 Answer 1


Cancer does what Cancer does

Even disregarding a lot of other difficulties the creature has to overcome, like losing body heat during intense activities, a body can't isolate Cancer. The prime reason why Cancer is dangerous is that it's made from the cells of the organism. This means it has all the enzymes and other flags that make the body identify, correctly, as it's own. That it's a dangerous mutation that will generally reroute blood vessels and such for more nutrients and in some cases grow wildly in any direction isn't noticed by the body. Some Cancer might mutate in such a way that they are cleared, but the one that are a health hazard are invariably recognised as our own body and thus not acted upon.

Isolating the skin layers and the rest of the body will not help, as some Cancer variants grow into any direction they want. Some variants can also be transported by the blood, which is an extra property of some Cancers, so an active system should be made in the blood for separation of the skin and the body, which is just wasteful. Even then it can nest close to the rest of the body and potentially grow into the precious area's.

I could go on, but in the very principle Cancer can't be isolated by the body.

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    $\begingroup$ Indeed the mechanism would not kill a cancer that is in places other than the skin, but if the cancer is just beginning on the outer layers of the skin self-immolation will kill it off. My father had skin cancer and now he doesn't have it (we didn't burn him, a doctor cut the cancer off and he's had no new cancers for years now). $\endgroup$ Commented Jan 7, 2021 at 15:18
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    $\begingroup$ @TheSquare-CubeLaw agreed. From the question I found he already knew it would be killed by fire in the specialised skin layers, but he wanted to specifically isolate Cancer in these layers to protect the rest of the body. That is impossible, (although you might be able to reduce the chances of that happening). $\endgroup$
    – Trioxidane
    Commented Jan 7, 2021 at 15:24

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