I'm trying to make a world with 1000 years of history, no population or site caps, and yet NOT have humans take over every square inch of land they can get their grubby little hands on. So far I've tried the following:
Extended baby/child stage: Under the assumption that creatures who are not yet adults cannot breed, I attempted to make human children turn into the toddler stage at age 3, and only become seen as adults at age 15. This has seemingly no effect in worldgen, and unless handled carefully can lead to cities overrun with children. They are smaller and easier to kill, however, so in a high megabeast environment, it does seem to cut down on the growth a little bit.
"Sterile" castes: Female for all purposes except for a [LITTERSIZE:0:0] token. Presumably these frigid women, whom I have making up 10% of the female population, should get married normally to otherwise fertile males, lowering the population count somewhat. It doesn't seem to have any effect on the humans' eventual domination of the world. I do, however, like this idea. Not everyone is a breeder. Some people might be gay, others genetically sterile, and still others simply uninterested in having children.
The biggest problem with the sterile castes is that they are considered a separate gender, so I can't make sterile males. [MALE] implies impregnation. There is no [LITTERSIZE] equivalent tag to make them not generate babyspores. And they're called "it" which I don't like on anything except the elves (who are pretty androgynous in my imagination)
Lower max civ sizes: Doesn't seem to work at all past the initial generation of the civ, since civs will still accept immigrants into their populations and ignore this cap. I am not sure where those immigrants are coming from, but in Legends mode they report as "Human" in all ways except birth (which I can't find listed anywhere... spontaneously generated?).
Limited Biomes: Doesn't work how I want it to at all. Civs will still use up every available inch of space surrounding their cities, up to the point that they do not support the next biome over. I did find out something interesting, in that an entity with
[BIOME_SUPPORT:ANY_DESERT:3]
is actually
less likely to spread than one with
[BIOME_SUPPORT:DESERT_SAND:1]
[BIOME_SUPPORT:DESERT_ROCK:1]
[BIOME_SUPPORT:DESERT_BADLAND:1]
Am I missing anything here? I'd like to be able to keep the artificial population caps off and be able to generate an organic, living world with 1000 years of history.
Oh, I've also tried changing the volcanism settings just in case, so "MAGMA" is not a proper answer