Medieval food consumption question

[legacyblade]

Hello everyone, I've run into a logistics problem when setting my fantasy story in an archipelago. In particular, the story takes place on an island home to an unusual ecology (silver trees, crystal mushrooms, orange leaves, vines that act like boa constrictors, etc.) I know I'm going to need to make this island relatively large (even though the humans only occupy a tiny part of it, supporting themselves by exporting a dye native to the island), but I don't know how large.

On this island, there is a race called the Faeleen. They farm humans to absorb their lifeforce (this allows them to live forever, not need to eat, and gain exclusive access to a powerful combat magic). Due to how I've setup lifeforce working (you use most of it when growing into an adult), the Faeleens harvest humans by preforming C sections once the mother is about a month pregnant (I decided since that's around the time babies get a heartbeat, that's when they'd be considered alive for the sake of my magic system). The Faeleens are at medieval level technology, and have grown enough that they have a few small nations. They're at the point where they'd start running out of room in their big forest. So tensions are high, but there's still enough room that they aren't motivated to settle areas outside their natural habitat.

So my question is as follows:

How many Faeleens would be required for a medieval society with about three nations? What percentage of them would be military? If each human woman produces a harvestable human baby about every month and a half (that's worse case scenario, since they would have bred them in such a way that twins are more common), and each of these harvested babies gives half an hour of magic use, how many humans would be required to make magic viable in battle? And how much land would be required to grow enough food for humans? Based on the ecology of this land, they'd either need to be fed on mushrooms or fruit, but I could make high nutriant plants. I just don't have a head for big numbers, so I'm not quite sure how much space would be needed and how much food would be consumed. Every time I try searching for things like this, I get diet tips x.x

Thanks for reading my long post. Sorry for the length and the oddness of the question. Any resources you could provide would be great!

- Note, the Faeleens mostly leave the humans exporting dye alone. Hunting is less efficient than ranching. Particularly when you can consume the offspring of your breeding stock after only a month or so of pregnancy. They simply don't see humans as a threat, and as such ignore the humans outside of the ones they've cultivated.

 

[The Unseemly]

If history's to show us anything, overpopulation = bad. There were many different events that caused depopulation. The Black Death was one, basically a massive pandemic that was terrifying to all those people cramped together. War, was another; people were recruited into armies, or cities/villages were otherwise ransacked by invading peoples. Malnutrition is the third example I can think off the top of my head. Due to the relative slowness of how medieval farming worked, food and water ran low when there were many mouths to feed. At this point, it was usually a process of natural selection: the strong, who got their food by whatever means lived, those who didn't, died.

Hope that helps.

 

[skip.knox]

I think you can pick your size. A "nation" can be nothing more than a single village, or it can be a hundred thousand. They can be thinly scattered, needing some substance (including humans) that is itself thinly scattered. Or they can be more populous and more concentrated. I doubt the specific demography is going to be crucial to your story.

You can look at medieval human society for guidelines. Population density varied pretty dramatically, though in general one can say it varied with arability of the soil and availability of a river.