Singing Herbs

I listened to a lecture the other day by a famous anthropologist about tribes in remote jungles discovering the healing properties of herbs. One treatment they discovered was of particular interest. They'd combine two plants that were both deadly on their own, dry them, and then shoot the dried powder into each other's noses during a ceremony. It would induce massive hallucinations but not kill them. The question I've often pondered, how did tribes find these plants that heal? And furthermore, how on earth could they ever find that combing two they knew to be deadly wouldn't kill them. I'd always assumed guess-and-check method over the course of thousands of year of accidental deaths, but he suggested something different. Of all the millions of plants and ways to use them, he said that perhaps the plants "sing" or resonate with the tribes on certain levels we're unable to understand. I'm as yet unable to consider a modern equivalent, except that I always seem to drink just the right amount of scotch to not get drunk but still wake up with a headache.