I haven't read of any cultures using a blowgun that did not simultaneously develope a toxin for the darts. I helped recover over a dozen ducks and geese that were wearing blowgun "broadhead" darts from Canyon Lake here in Rapid City, SD some years back and there was not a single fatality observed. Think of it this way...if a wire poked a hole in small game and killed it, then veterinarians wouldn't give rabies shots for Fluffy and Muffin anymore.
I hope I am not coming across as too sarcastic, but when you see a beautiful canada goose with a blowgun dart in it's head swimming around a family park you get a little peeved.
And before anyone cries "hippocrite", yes, I own a blowgun, and yes I use it...just not for hunting. Ever play darts with a blowgun? After a game or three you will find you have to step back to about 15-20 yds to make it challenging again.