There is no kick to the ba... beard? like embarking with a civilization that's been dead the last 7000 years (did you really generate a 10k year world

) or so, without knowing about it. The fact that civs die off during worldgen sometimes is probably the only feature I really don't like about the game. It would be nice if there was a choice you could make before generating a world which would make sure civs can't lose their last site or something. Even more so for any new players or anyone who doesn't know about it or how to check for it before-hand.
Okay, now for something that might actually be helpful.
What I do is check the world when it finished generating and keep a lookout for human/dwarf/elf/goblin owned sites ("DWARVEN mountain halls" or "ELVEN forest retreat" for instance) while checking if the world looks interesting in general. Might be hard to find them so I usually continue by exporting the text files from that same screen (I think it's 'p' but it's listed at the bottom).
Open the "region4-world_sites_and_pops.txt" (number depends on the world) and make a search for the civs you're interrested in being alive (for instance ', goblins' to see if there are any sites run by the goblins or ', dwarves' for dwarves or ', kobolds' etc).
Humans seem to always get by in the newer versions though, maybe partially since they have a huge load of villages and a civ can only attack max one a year.
I then always select the largest dwarven civ I can find because I'm paranoid and believe the chance is better they're still alive (can you pick ones that aren't if it's not the only choice?).
If someone knows a shorter process (or if there's any problems with mine) I'd like to know. So far no dead races slipped past so it seems to be working fine.

edit: I usually keep the worlds pretty young (round 200-300 years) since I'd like to think chances are better for everyone to stay alive until the game starts that way. . .
edit2: Accidentally clicked quote instead of modify, sorry about that. . .