What would the physical effects be to Elves if they began living underground?

Question

Background:

An Elven nation that once thrived for thousands of years as a predominantly agricultural race was forced underground because of unexplainable occurrences of extreme weather conditions (tsunamis, volcanic eruptions, hurricanes, blizzards) threatening their existence. The majority of weather this continent has experienced is sunshine, with the occasion of thunderstorms and rain. Having no previous experience with other weather conditions, the Elven nation migrates underground to prevent themselves from becoming extinct.

Factors to consider:

• These are the first Elves to exist, so any other species of Elves came about as a result of reproduction.
• There are around 100,000 Elves belonging to this nation.
• The majority of their food is plant-based but they occasionally eat meat.
• Their sight and hearing are better than that of any human.
• They are typically 6 feet (1.8 metres) tall.
• They are born with green eyes or blue, light brown hair or blonde.
• Due to sun exposure, they are mostly tan-coloured.
• These Elves live for 300 years buy only reproduce until they are 100. In this time, they have between 2-5 children.
• The extreme weathers are frequent but not constant so they do make surface trips for resources.
• The nation survives underground for at least 5,000 years.
• Although they cannot cast magic, they have some magical attributes such as longer lives and are more immune to diseases than humans.

Although it is unrealistic to suggest it has no effect on their sight, I would prefer they didn't go totally blind.

(Edited to ask only one question, be more specific, and to fix errors. The question asking how they would survive now has its own post. See: How would Elves survive underground without prior experience?)

Answer 1

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

Answer 2

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.

Answer 3

Go ahead and google up some eye candy Drow hotties. Out of your system? Good. Let us set aside magic and consider ecosystems and evolution. No magic.

Elves are long lived primates; cousins of humans. They are intelligent, cooperative, slight of build, with a well developed culture.

Evolution means selective advantage. Certain traits give some elves the ability to have more children. Elves without those traits have less children. Let us consider also that the shift to cave dwelling occurs over many generations to give evolution time to operate. As the surface becomes less hospitable, elves which can support themselves on the resources of the underworld are more likely to have children who themselves survive.

Meet the Elf Olm-Sloth.

1. Slowest possible metabolism. The surface is resource rich thanks to the sun and rain. The underworld is resource poor. Calories are scarce. The olm is a subterranean salamander with a metabolic rate slow even by amphibian standards. Sloths have super slow metabolic rates too so it is possible for a mammal. Slow metabolism means your calories go farther and you are less likely to starve. Your underelves would slow... way... down. She may be capable of a burst of speed to snag a fish, and then she rests.

2. Noncooperativity. Hunting and farming are methods to exploit the caloric wealth of the surface. Cooperativity helps with both endeavors. Gathering fish and bugs would be the way of the underworld. Gathering is not helped by cooperativity and in fact the more you spread out the less likely you will deplete resources in any given place and starve. Your underelves are asocial loners. Their culture falls away.

3. A corollary of 1 and 2: slow thought. Things do not change much in the underworld. There are not complex spatial problems to be solved, or problems of complex interpersonal relations. Curiosity killed the cat. Your underelves are uncurious.

4. Semiaquatic. Concentrated food resources in the underworld are in places where water can carry down some of the bounty of the surface - nutrients at least. Your elves become semiaquatic, because the water is where the fish and bugs are.

5. Small. Related to #1 - the smaller you are the less food you need. Large physical size is a drawback in the underworld. You need more calories and have less access to small spaces. The generations will dwindle your elves to shriveled monkeylike miniatures. At this point you can go google up some more Drow babes if you need to.

6. You're back! The underelves don't care how homely they have become because they are blind. It is dark down there and the prima donna eyes demand a lot of brainpower that they cant use. Hearing, smell and especially tactile vibratory sense become the dominant senses.

7. Smelly. If you are a tiny blind loner who lives alone, how do you find a mate? Sniff him out. The underelves stink pretty bad. This scent marking serves to mark occupied territory against incursions of other underelves. The diffuse funk also cannot be used to specifically locate another elf individual, which is protective because the underelves are

8. Cannibals. Of course they are. Calories are calories and an elf individual represents years of caloric accumulation. It is evolutionarily disadvantageous to eat a potential mate, but nonmates are definitely fair game and a big score as regards calories.

I hope one of you will see fit to draw Drizzt Do'Urden as the blind stinky stupid cannibal water monkey.