5
$\begingroup$

Some form of chemical reaction interacting with the digestive system for a start?

$\endgroup$

4 Answers 4

4
$\begingroup$

I suggest you read about Spontaneous Human Combustion. Lots of people have died in a fire without a proper explanation, leading many to conclude those people simply caught fire by themselves.

The scientific consensus is that it doesn't happen. However, many hypothesis have been proposed for the phenomenon. They are listed in the wiki and I am quoting the three I find most scientifically plausible below:

  • The "wick effect" hypothesis suggests that a small external flame source, such as a burning cigarette, chars the clothing of the victim at a location, splitting the skin and releasing subcutaneous fat, which is in turn absorbed into the burned clothing, acting as a wick. This combustion can continue for as long as the fuel is available. This hypothesis has been successfully tested with pig tissue and is consistent with evidence recovered from cases of human combustion.

  • Brian J. Ford has suggested that ketosis, possibly caused by alcoholism or low-carb dieting, produces acetone, which is highly flammable and could therefore lead to apparently spontaneous combustion.

  • Inhaling/digesting phosphorus in different forms can cause the forming of phosphine which can autoignite.

And then of course there is my future causa mortis, which is me bursting into flames the day the devil thinks my work on Earth is done and calls me back home.

You can pick any of those for your humanoid creatures, or a combination to make it even more plausible. Perhaps their diet contains a lot of phosphorus (fish are rich in that), perhaps they are very fat and live in areas prone to wildfires - only its not trees that are catching fire, but rather people. Perhaps they are all alcoholics on Atkins. Perhaps they all listen to heavy metal (it comes from hell!)

$\endgroup$
3
  • 2
    $\begingroup$ It should be noted that most of these explanations point to combustion that is not spontaneous in any sense of the word - it's just people getting set on fire the old fashioned way, albeit by a non-obvious ignition source. $\endgroup$ Aug 24, 2023 at 19:36
  • 1
    $\begingroup$ @NuclearHoagie I'll concede wicks and Satan but ketosis and phosphorus burning from inside sound sponraneous enough to me. $\endgroup$ Aug 24, 2023 at 21:21
  • 1
    $\begingroup$ Wortb noting in relation to point 2, is that diabetics (chiefly type 1, but also advanced stage type 2) can have elevated, even lethal, levels of ketons, caused by inability to metabolise carbohydrates, which is in turn caused by insulin insufficiency. $\endgroup$ Aug 25, 2023 at 7:59
3
$\begingroup$

This answer will probably be laughed at, and that's okay. My first thought was... bananas.

While a banana in the beginning of the ripening process might become sweeter and turn yellow, it will eventually over-ripen by producing too much of its own ethylene. High amounts of ethylene cause the yellow pigments in bananas to decay into those characteristic brown spots in a process called enzymatic browning.

So what if your humanoid has a similar situation?

Mix that with this:

All objects, including human bodies, emit electromagnetic radiation. The wavelength of radiation emitted depends on the temperature of the objects. Such radiation is sometimes called thermal radiation. Most of the radiation emitted by a human body is in the infrared region, mainly at the wavelength of 12 microns.

Maybe after death their bodies radiation "over-ripens" and increases until boom.

$\endgroup$
1
  • $\begingroup$ I didn't laugh at this at all. I never knew that the browning of over-ripe bananas is caused by ethylene, and I found that interesting. Whether a human body could over-ripen in a similar manner, and then combine with its own thermal energy to spontaneously combust is probably questionable. However, the train of thought is interesting, and that, in and of itself, deserves credit. $\endgroup$ Aug 25, 2023 at 19:15
2
$\begingroup$

If you are looking for a potential explanation in a parallel world, chemical reactions alone are less likely, but some sort of organism (like the yeast used to make alcohol) could be present and produce flammable compounds. To achieve spontaneous combustion, you need two different compounds that are hypergolic. The simplest way would be to invent some organism that exudes nitric acid. This could combine with the alcohol and spontaneously ignite.

$\endgroup$
1
$\begingroup$

If it is anything human-like - no chances, ~60% water. Spontaneous combustion would be hard to explain based on organisms we know, science-based is a rather tall order. It's xenobiology though.

Let's say they are like Protoss. High psionic abilities which become part of basic organism physiology. There are benefits - high resistances, speed, strength, etc. But when a person dies psionic components of the body shuts down and the remaining part can't exist without them in normal space. To avoid indignity of turning into pile of **** the race tuned their biology to make remains burn instantly.

It may use an alien technology device like ring or collar.

Depending on the story, it can be a safety feature to make sure dead special agent doesn't have his brain scanned.

It can be based on alien's religion, a special practice/tools that prepare person to death.

Nano machines activate with death, quickly get rid of water, turn everything else into highly flammable substance and initiate the fire.

$\endgroup$

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .