Village's don't get new people in 'em. Njerpez warriors spawn randomly though, so if you're like me, who got lucky and started in an area where both those, animals and even foreign traders roam, you could have a permanent food supply out of humans.
Apparently though, that's supposed to be bad somehow, I don't know how, but spirits apparently don't take kindly to cannibalism. Maybe it's actually just a thing that's being said and it doesn't have any in-game punishment yet.
Anyway. Njerpez, random spawns happen all the time. You can enter their camps, and kill every single one of them, and turn them into bunch of delicious meat. However, once a camp is emptied, there won't be any Njerpez there later on.
I've emptied only one camp so far during a night raid, so I can't say if it effects spawn rates. It might simply be that they're spawning out of the camps nearby and if I wipe those out, less to no Njerpez.
Anyway, carrying on.
You CAN empty every village, settlement and camp of people and eat everyone if that's your gig.
Starvation? Worry not, because you can walk far enough on the world map to get to the map border, and if you pass further from there, you can go to a whole new map, that's regen'ed, and filled with new villages and meat people.
At least that's what I remember doing in the last version. I figure I wanted to check out some new place after the whole "well that's one house done".