In my world, I wanted to have a specific type of creature (a human based one) who are called the Sealed.

Basically, the Sealed were forced to go underground into a large cavern after WWIII’s aftermath, and stayed there for many generations. I know technically they wouldn’t have enough time to evolve into a new species (since my world takes place 230 years after) but I had some adaptations I wanted them to have, and wanted to know: Is this creature likely to evolve these traits given the conditions it lives in?

  • I want them to have extremely, extremely pale skin (almost to the point of Albinism)

  • I want them to have pupils enlarged to where their eyes seem fully black, in order to see in dark conditions.

  • I want them to have a reversed sleep cycle (ie They still operate of 16 hours of activity and 8 hours of sleep, but they sleep during the day and are active mostly at night)

  • Important thing: I want it to be extremely, extremely hard for them to surface into the post-apocalyptic world without good protection during sunlight hours.

  • $\begingroup$ An interesting concept, though I'd be rather surprised something like this hasn't been asked before. Main issue I see here is that you've already shot your concept down and you've already given us the reason why it can't work, given real world mechanics anyway. So, what's different about your world that would give us a shot at making this happen within the desired timeframe? Am only voting to close until you can edit for clarification! $\endgroup$
    – elemtilas
    Sep 28, 2020 at 0:08
  • $\begingroup$ 230 years! I'm pretty sure that is more than enough. In Metro 2033 people living in the metro for a couple of decades can't go out during the day otherwise they go blind. Our current lights also damages their eyes to if they go to a place brightly lit, what we say is normal, they wear special glasses. Children use a lot of vitamins to help them grow healthier without a sun. Your people might will adept to the climate, hot or cold, and other conditions. Probably acrophobia is another major problem. Such a long time will change everything about them down to their genetics. $\endgroup$
    – Seallussus
    Sep 28, 2020 at 0:09
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    $\begingroup$ "Extremely pale skin": Swedes. "Pupils enlarged": any human with dark-adapted eyes; just wait about 15 minutes in a dark room. "Reversed sleep cycle": any human working night shift. $\endgroup$
    – AlexP
    Sep 28, 2020 at 0:17
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    $\begingroup$ @Seallussus Are you citing a videogame as scientific research? $\endgroup$
    – rek
    Sep 28, 2020 at 0:23
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    $\begingroup$ Evolve? I reckon I meet your criteria as is. Photophobia. Pale skin. Works at night. Doesnt like going outside. Yeah your new race is "Software Engineerus". Seriously though see worldbuilding.stackexchange.com/questions/184859/… $\endgroup$
    – Ash
    Sep 28, 2020 at 1:52

2 Answers 2


Founder Effect:

While evolution is unlikely to result in major changes in the short time period you are looking at, much of this can be basic non-genetic adaptation. If, however, you want your people to be genetically this way, I suggest that the people going into the bunker were already pre-selected to be different.

People who might find it attractive to be hanging out in bunkers underground in case of WW3 are either extremely paranoid OR they have some underlying condition that predisposes them to want to be in dim, light-controlled environments. If you want, why NOT make albinism common in your population? I imagine a community of albinos who came together and decided to follow a more subterranean lifestyle. There are albinos with dark eyes and hair as adults (after foveal development) and a mild version of albinism would result in some visual problems but a fairly normal appearance as adults. Perhaps a mutant OCA2 gene with green eyes.

But if albinism isn't your thing, how about one founding family have abnormal pupils? You just say General X (or his beloved wife) had a genetic anomaly (a variant form of congenital mydriasis, and it can be an autosomal dominant disorder for good measure. This case is of an older woman, so some variants do not have underlying significant neurological problems), and because his/her eyes wouldn't dilate normally, he/she was naturally attracted to what would in the military have been a less prestigious job - nuclear preparedness. Of course, he made sure his kids would be close by in case they all had to go in the bunker - and his kids had it, too. Once in the bunker, those with the dimness adaptation had positive pressure to select - they were better at seeing in the dim conditions, and daddy (General X) was in charge. For life. Who wouldn't marry into that?

Migraines can also make people sensitive to light, and migraines frequently run in families. An initial enrichment of your population with people that have frequent migraines would result in a population that preferred a constant stable environment and low light levels.

Pale skin could also be a founder effect, as a bunch of Scandinavian folks are your bunker dwellers. Alternately. people with red hair are more vulnerable to the effects of sunlight, and I can envision if in the future (or an alternate present), if folks had wanted to escape the effects of widespread ozone damage, underground work would have been a good assignment (especially if general X had a soft spot for recruiting redheads). They would get sunburn easily and freckle a lot in the sun. They can be more sensitive to pain, as well as cold/heat, and taken to an exaggerated level, they would find weather to be unpleasant.

Further, agoraphobia is the fear of the environment, and fear of open spaces. Isaac Asimov had the whole population of Earth suffering from agoraphobia in one of his novels, The Caves of Steel. A society of people who spent their entire lives indoors and underground might easily be wildly agoraphobic, especially if they were prone to anxiety disorders (as people paranoid enough about nuclear war to want to live in a bunker before a war might be).

So I envision a society of big-eyed, green-eyed, red-haired people with anxiety disorders and a familial pupil abnormality. This fits nicely with ancient myths of the Irish Tuath de Dann, the people exiled from the surface to live in their underground realms. No story is complete without tying it to mythology, somehow.

Sleep cycle is easy to explain. Without any external reference, people can keep any schedule they care to. Again, after enriching for an initial population that dislikes sunlight, they may have already have been following a night/evening shift schedule.



Or at least, not all of the features you want in quite the way you want them!

Conditions: a group of people lives underground for 230 years. This is some time between five generations at the least and 20 generations, since there's nothing else to do in a cavern.

The reason this is a no is quite simply as you already say: there is not enough time for all the features you want to become what is essentially a subspecies of the original human-like progenitors of the Sealed. For comparison, 230 years only takes us back to 1790. While it might be argued that human civilisation has devolved considerably since then, the physical species itself has not appreciably changed, except in so far as improvements in diet and medicine have changed things.

There are four characteristics you want, and a couple of them are indeed possible.

  • If you begin with an initial population of pale skinned humans -- or better yet, proper albinoes -- then your resulting population after 230 years will be pale skinned. So far so good!
  • There are instances of congenital mydriasis, but you really don't this gene mixing into your population! Some of the problems that go with the manifestation are life threatening. In any event, normal human eyes can adjust to low light conditions well enough: if there's any light in the caverns, folks will be able to see a little bit. If there's no light, then no amount of pupillary dilation will help them.
  • Sleep reversal is possible. Check out the results of the sleep cycle cave experiment. Family & clan groups will naturally create and adjust to an approximately 24 +/- hour cycle of activity & rest. If the fictional world is Earth-like, has a Moon, and has a 24 hour day, your Sealed will end up with a cycle within those bounds. They may or may not be prepared for the 11-7 shift, unless they have access to some kind of time keeping device!
  • This is the easiest: albinoes already require protection from the Sun, even more than ordinary pale to olive skin tone people (tanning is definitely nòt healthy for skin!). The Sealed won't have had enough time to evolve anything like permanent mydriasis, but if their forays into the Outside are temporary, then they might just opt for serious eye protection (like a low shade welding glass type protection).
  • $\begingroup$ Yeah there’s light in the cavern. They can still go out at night, and fire has not been lost to them. $\endgroup$
    – DT Cooper
    Sep 28, 2020 at 3:21
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    $\begingroup$ Also, as long as their at least noticeable different from your average Wastelander and vulnerable to sunlight, I guess it could still work. $\endgroup$
    – DT Cooper
    Sep 28, 2020 at 3:24

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