Is it possible to civilize intelligent wilderness creatures in the course of a fort's life (on site or elsewhere in the world) or is civilization of wild sentients a world gen event only?
Basically I made a fort near a biome that contains massive animal people in the hopes they'll want to move in. None of the which were available by default in adventure mode. They're playable from the species select list, so they exist in the world, but aren't already part of any civs.
I had a boar woman scholar visiting my fort recently. I think some of them are already civilized.
Yes, that's the point. During worldgen some animal-man tribes civilize, in your case a tribe of wild boar-men civilized at some point. You can check Legends to see exactly when this happened.
However, Toady says that until animal-man entities have been more fully fleshed out, there won't be any additional animal-men civilizing during play.
Of course, I suppose you could always create a thousand 'intelligent wilderness adventurers' and settle them all in a village somewhere to manually kick-start the process.