I'd love to speculate about how ayahuasca was discovered. I've heard shaman saying that "Ayahuasca told me about it" but that sort of tautology doesn't cut it. But why would people choose to ingest two (or more) plants that taste like absolute ass? My theory is that b. caapi was primarily used as an emetic and anti-parasite before its enzyme inhibition was disvovered. Still, for anyone who has drunk banisteriopsis caapi tea, it tastes utterly disgusting, so I wonder how anyone would have decided to continue drinking it after first gulp.
Mysteries. I guess that our western mind cannot understand implicit cause and effect, we need it explicit.