Jtdcftul

Let's say that this particular Elven nation once thrived for hundreds of years above the surface as a predominantly agricultural race. They can have green eyes blue eyes, blonde hair or brown hair, but all have tanned skin due to working outside under the sun most days. Unexplainably, extreme weather conditions like tsunamis and hurricanes start frequently occurring and are threatening to wipe out their existence. This continent has only ever had mild storms, light rain, or sunshine the rest of the time so these Elves had no previous experience with these conditions. Taking drastic action, they decided they would relocate their nation underground.

To help clarify and be more specific, here are some factors to consider:

• These are the first Elves to ever exist, so any other types of Elves came about as a result of them reproducing.


• There are around 10,000 Elves belonging to this nation.


• The majority of their food is plant-based (typical) but they do also eat meat on occasion.


• They have little experience with building with anything other than wood, but they will have to get used to it.


• Their eyesight and hearing are excellent, though I'm sure that will change as a result.


• They are around 6 feet tall, or 1.8 metres.


• They will have constant light down there because of torches and fires, but its not a replacement for sunlight.


• Their level of technology and advancement closely resembles that of the Medieval Ages or earlier. They have invented the wheel if that helps.


• I would like them to survive for at least 500 years.

Basically, how did fantasy Dwarves begin living underground and survive for so long and instead apply that to an Elven race.

Then, I want to know what would happen if after 500 years or more, half of them decided it was safe to live on the surface once more. What effects would it have on them?

Food production

The big hurdle you have to overcome for your scenario to work out is food production. Essentially all food production we know relies on sunlight as it's source of energy. Meaning either plants take up sunlight during photosynthesis and store it in various forms of starch, etc., or animals eat said plants, take up the suns energy "second hand" to be then themselves (or their eggs/milk) eaten by your population. And, by the way, mushrooms are not a get-out-of-jail-free-card, as they rely themselves on (the suns) energy being stored in other microorganisms they rely on (see this question).

You will essentially need some stable, sustainable food production, either plant or animal-based, that will allow your elf population to survive in the long term. This either means some magic/handwaving/unobtainium/etc. or some sort of production cycle that relies on plants/animals/fodder or some other biomass being brought in from the outside world. So unless you come up with a magical solution it is unlikely that your elf population will truly live without any ties to the surface world.

The only idea I can come up with is to mainly rely on hunting animals (fish, moles, snails, ...?) that live underground but themselves travel to the surface or rely on surface food/nutrients somehow reaching them (e.g. via underground streams). This could be supplemented with some gathering of e.g. mushrooms, snails, worms, mussels, ... leaving you with a hunter-gatherer society.

Physiological change

The 500 year time span you mention is far too short for any kind of evolutionary changes, even more so if the elves are long-lived like most of their fantasy counterparts.

What you would see is reduced Melanin production, so your ground-dwelling elves would become rather pale. Their hair would not be bleached by the sunlight, so might be a tiny bit darker, but that would be it: overall no big change would occur.

If your elves rely on some vitamin that is only produced under the effect of sunlight (as we humans do) then they are out of luck: they'd have to either find a supplement vitamin source (maybe some animal they can hunt?) or will perish rather quickly.

Societal change

The societal change will certainly be the largest, especially within the given time period of 500 years. The first one or two generations might still be in 'survival mode', fighting with resource shortages and trying to get accustomed to the new situation, the newly available (or no longer available) resources, adapting to their immediate surroundings, etc. This would certainly be a big struggle, and a fair number of your population might starve. It is also likely that the sudden shortage of resources would lead to the formation of strong families/clans with infighting between them, so complete splits and the formation of new 'nations' might be possible.

After that the society would probably slowly settle in and optimise their new hierarchies and organisational structures to work well with the new ecosystem. In the long rund I'd expect your 'nation' (actually, 10'000 individuals is rather the size of a small town) to disperse in smaller settlements that consist of maybe some dozens to a few hundred individuals: because they are largely based on hunting they will need to cover bigger territories/hunting grounds to sustain the population without completely decimating the hunted species - similar to how human population was organised in the pre-agricultural hunter-gatherer times.

In the long run this will necessarily also lead to the tech-level of your society dropping markedly: a society based on a base unit of dozens/hundreds of individuals is simply not able to sustain the additional burden of the technology, the supply chains, the passing of knowledge, etc. that bigger societies can.

As the number of generations since the migrations grows the memories and stories would slowly grow more and more distant... It is rather likely that the increasingly distant past of the elves' surface-origins would then fade over towards some sort of origin-myth or religion, maybe with some deities being responsible for the migration (weather, storm, ...), or some new ones being invented that now shelter the elven population (rock, earth, ...).

Summary

So again, summarised, I would predict the following changes:

• Struggle for food during transformation to hunter-gatherer society


• Formation of strong family ties or clans


• Separation into small family/clan based settlements


• Marked drop of tech level


• Formation of new mythology based on the surface origin

We may have rushed underground too suddenly. The resources to keep us at our 10,000 strong vanished with the sun.

A month later, people started to die from starvation. At first it was the Elders, who gave their foods away. Then, the sick, the skinny, and the parents and children. It was devastating, leaving us with under 1000 people and without the wisdom of the elders.

We didn’t know how to pick the stone ground yet, so we took the bodies into a lone chamber about half a mile away, and sealed the entry with stones. Moving bodies I was surprised to see some people had been gnawed on with jaws too large for a rat. We needed order, we needed leadership.

That’s why I became the shaman. The food was gone, torches were almost all burnt away and we were on the brink of mutiny. There was a clean underground lake that provided us with water, but not much else had been established since the elder’s died.

I had read of rocks that burn, deep in the bowels of the earth, so I sent almost all the people we had into the depths of the caves with all but one of our torches to pick out samples from every different rock and mineral they could find. With purpose people sprang into action, but I could feel the doubt eating them away like hunger. When they returned most just brought pretty rocks, but we did make some discoveries and learn more about what stone can be used in what way. 3 groups of 5 elves never came back though, and another 4 sick died that night.

I was pounding my head for answers, trying to search for answers to our problems, but I was to hungry to think. I cried my self to sleep for dooming our people further but dreamt a stupendous dream! I was back on the farm, mixing manure into the dirt for the next season. I remembered the weight of it, the stink, and how much it had bolstered our plant growth in the past year. Goat shit had become a business, and everyone wanted more.

I woke up with a start, and was excited for the first time in a month. I traced back to a cave we passed through in our decent, and heard the flapping of leathery wings and the squeaks of rodents. The ground was piled high with excrement, there must have been thousands of pounds. I grabbed for a stack, but it was deeper then I though. I pulled up and there was more underneath! I reached for the bottom pile as it had the most time to dry out, then in the entrance cave lit it on fire as was welcomed with a soft warm glow. I screamed and cheered for at least an hour, then had to calm my self down. I didn’t have the energy to waste screaming, and people were on the brink of eating one another.

Extreme weather... What would it actually do? It would prevent agriculture. It would feasibly destroy houses and most public buildings. It would kill the vast majority of your elves, mainly via famine and disease. That last bit is important to remember for the social effects.

Effects on the ecosystem at large? Since we are talking about extreme we can probably say that trees will be gone. I mean, if the trees could survive, it would be fairly easy to create buildings from wood that would also survive. So the landscape would probably be something like prairies or savanna. Grasslands with occasional small trees or bushes.

We can also assume common flooding and extreme erosion. Grasses are actually good at dealing with erosion and lack of rain is a major issue with the Earth analogues I gave, so it would probably be very rich and productive ecosystem but with spectacularly deep canyons or gorges for the rivers.

For animals you'd have antelopes, horses (or zebras), and some sort of bison/wildebeest equivalent. These would be hunted by lions, leopards, wolves. You'd also need scavengers such as hyenas. Very rich ecosystem very similar to one we have all seen in various nature documentaries over the years.

The point I am trying to make is that even with agriculture being impossible there is going to be lots of food outside. Lots more than underground, certainly. Your elves will live in the caves and hunt the animals outside. Maybe ones that come to drink at the river valley their cave overlooks. In short, they will live almost exactly like our ancestors lived before the agricultural revolution.

It would be fairly easy to assume that the weather is worse than this and there won't be rich ecosystem outside but, let us be honest, if the weather is so extreme that grasses cannot survive it, everyone will die. And something will be hardy enough to survive to eat those grasses. Or elves certainly will not survive.

Your elves would start with iron working, large scale organization, and knowledge of architecture. They would gather survivors, maintain order, scavenge all the tools and valuables they can find. The drop in population would cause major social changes (no large kingdoms) but medieval technology should be sustainable, if the elves stay organized.

This works much better if there is a nearby cave system that can hold thousands of elves that they can withdraw into and indeed have withdrawn in the past during wars and such. The end result would be independent elven communities with sizes from a small village to a small town depending on the size of the cave system available.

The elves would have the ability to expand their caves for more space. They would also build small gardens protected from wind and flooding. Eventually they might develop mushroom farming but initially they wouldn't have the space to do it to an extent that makes a difference.

Fires would be an issue because the storms would destroy most trees, so after the initial windfall gets burned or swept away, they'd have to start burning compressed manure collected from outside. While some trees would survive due to protected locations, those would be the exact locations where you'd want to build a garden for fruits or vegetables, or even build a house on. Far too rare and valuable to grow fire wood on.

Given the size of the settlements they would probably be chiefdoms, they'd be run by a chief, probably a descendant of the leader who founded the settlement, but probably with the approval of "clan elders". Sometimes decisions or chiefs might be discussed publicly and even voted on.

Religion would probably be shamanism of sorts. people would probably mainly want good luck with hunting and avoid bad luck with weather, famine, disease, so a combined spirit talker, witch doctor, wise man like a shaman would be quite appealing. Specialized priest or organized religion would generally require larger societies. And more wealth and leisure time than shell shocked survivors could provide. Besides after the weather suddenly turned against them people would quite reasonably blame nobility and priest for angering the gods. They might be quite devout and religious but organized religion with priest and dogma would probably not be that appealing.