I have an idea for a society of humans who have a level of technology similar to that of the North Sentinelese Islanders: borderline stone age with maybe some ability to use metal. The population can be anywhere between 100 to 200 people. They mostly live in a cave system, getting all of their food from the caves and living there for most of their lives. Some people might leave the cave to forage, but they will rather travel farther than five miles from the cave & usually only leave the cave for about 10 hours a week maximum before returning. They usually forage at night because their night vision makes them sensitive to daylight. Would such a civilization be possible or feasible? Could the people be able to feed of the flora and fauna of the cave (as well as a few foraged goods here or there from near the cave) and still maintain their population/way of life?
A prerequisite for such a tribe would be an underground fresh-water source, or at least one very close to the cave system. It could be a river that runs underground for a stretch. If such a water source has plenty of fish and crayfish, perhaps even turtles, that could be a major food source - and probably a necessary one for such a scenario as you describe.
Mushrooms can grow underground if the conditions are humid enough, but they are unlikely to be much more than a supplement - there isn't all that much nutrition in a mushroom.
Bacteria and other single-cell lifeforms, such as archaea, are plentiful underground, with a total mass of roughly 15 to 23 billion tonnes of carbon. It might be possible to harvest such life forms for food, though I don't know how edible they are or how easy they would be to harvest.
Foraging above ground would allow the tribe to supplement their underground food with fruits, nuts, roots, herbs, honey, and the occasional wildlife (setting snares and traps would be a good strategy). This would add to the variety of their food; in particular, fruit would supply vital vitamins and can be dried or boiled with honey to make jam. Firewood can also be collected for heating and cooking.
Given all these sources of food, survival would be possible, I believe. The question remains why they would choose to remain underground most of the time. Maybe the outside is too cold, as in the Ice Age, when cave dwellers were common. Or maybe there are dangerous beasts or rival tribes roaming the neighbourhood in daytime.
Escuché que en un país existe una isla donde las personas de allí viven en cuevas. Si alguien de otro lugar o personas que no pertenece a ese lugar van allí, entonces los matan y se los comen. Así que sí pueden vivir en cuevas la mayor parte de su vida, solo tienen que adaptarse a ella.
There are several tribes that move away from the modern and go to live in distant places or people far from everyone who continue with their customs.
I heard that on an island there are people far from the "world", they live in caves. If someone who doesn't belong to that island goes, then they eat it. (They are carnivores) but based on what you say, they can live most of their life there, since they laughed similar to the previous times.
I hope I was clear because I don't know much English.