Consider the following scenario:

  • A world hosts a primitive civilization. This civilization is very basic, approximately stone-age but has not discovered fire yet.
  • The ancestors of this civilization once lived in light, meaning that they evolved to have eyes.
    • The world could have been impacted by an event that caused it to be engulfed in darkness
    • A space-traveling civilization could have crash-landed or colonized this planet, and through some unfortunate means lost all technology and reverted to this primitive state
    • Any other scenario taking place so humans with eyes inhabits this planet
  • Stars must be taken into consideration in that the primitive civilization must not be able to see them
  • Nothing on the surface of the world naturally creates light, such as bio-luminescent species or volcanoes

Everything else is fair game. How does the planet provide a hospitable environment (minus light) for these humans? What is their source of heat? What is their diet? What would prevent them from discovering light-emitting occurrences such as fire or electricity until their eyes devolve to being unusable (say, 10 thousand years)?

  • $\begingroup$ If they are humans (like us), I'm pretty sure they will all die from Vitamin D Deficiency before getting the chance to evolve. $\endgroup$
    – Timmy
    Jun 8, 2016 at 14:00
  • 1
    $\begingroup$ No time for a full post, but consider checking out The Time Machine, by HG Wells. He has a scenario very similar to this, enabled by two distinct civilizations... one of (essentially) slaves and masters, both relatively primitive by modern standards. $\endgroup$
    – eykanal
    Jun 8, 2016 at 18:28

2 Answers 2


Part one: food

All ecosystems on Earth depend on autotrophic beings participating in the food chain.

If your fictional people have no access to what we call visible light, plants as we know them won't do. That leaves us with four alternatives:

  • Chemosynthetisizing bacteria. On Earth they are usually found solely on the bottom of oceans, on termal vents. In a fictional world, chemosynthesizing algae could maybe feed the world for a while, but they need a steady supply of organic matter and a source of heat that might not be feasible to work with.

  • Radiotrophic fungi. The stuff of nightmares. In our real Earth there are fungi growing inside Chernobyl's plant that can do a process that is related to photosynthesis - but they use melanine to absorb gamma radiation instead of visible light. Supposing your fictional world has high levels radiation (and life in general has adapted to it somehow), such fungi could be the basis of the food chain. Maybe the planet is covered in clouds that let UV, X-rays and gamma rays into the surface of the planet, but not visible light. You could conceive a fungus that absorbs UV if you'd like something less extreme and lethal than gamma rays.

  • Deux Ex Machina. Technology from the precursos of current humanity includes machines that synthethise food. Life mostly thrives around places where such machines exist.

  • Leftovers. There is a lot of food lying around to be scavenged (honey, which can last for millenia; or maybe frozen animals if humans are living on glaciers, they just have to dig for it). The amount of available food in the world will be going down fast, so humanity will be on a race against the clock. But if you just froze the entire world really fast, people would have the mass of the whole ecosystems of Earth to eat before they started to starve.

Part two: heat

Not a hard one. Think of Venus. It is covered permanently in clouds. The reason that planet is so bright in the sky is that it reflects most of the light that reaches it. Very little sunlight reaches its surface. Yet its average temperature reaches up to 864°F, due to greenhouse effects.

It doesn't take much suspension of disbelief to accept an Earth-variant covered in clouds, where no sunlight reaches the surface and the temperature is within any range in which humans could live.

Part three: maintaining darkness

You could prevent people from (re)discovering fire by having a very oxygen-rich atmosphere. Anyone who tried to make a little fire would die in an explosion. In time people would learn they can't start fires.

A strong enough magnetic field, the kind that causes auroras but even stronger, could prevent most forms of electricity from becoming useful to humans - electronics would not work, electric energy could become hard or impossible to use if the field keeps changing in impredictable ways. Auroras may be blocked from sight by thick clouds (which would also serve to block starlight).

Last but not least, life in this planet may evolve so that no lifeforms ever develop the DNA for synthesizing luciferin, nor other light-emitting compounds. At least not where humans could see them... Remove fireflies from the world and most people will never see a bioluminescent creature.


One way I could think of solving this is by having them crash on a planet that has large expansive cave systems that are rich in fish and heated by geothermal activity. Maybe a hostile outer environment keep the humans from exiting the caves. Due to the easily available food they are able to stay alive even though their technology is failing them and eventually they make a life for themselves in the darkness. The fish keep them with a source of vitamin D (which they would need without sunshine).

Even as they through generations delvelope a primitive culture that is quite adapted to the caves the upper levels of the caves are still avoided due to the hostile envirinment outside.


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