I was reading recently that cultures with the best chance, over time, of sustainability, most likely to expand and grow, are the ones which nurture an undercurrent of irrationality. When it comes to cultures, dominance depends on size and stability, and in the case of human cultures it appears the ones most likely to excel are those whose practitioners are most willing to sacrifice self-interest to the betterment of what they see as their cultures superiority, as delusional as that may be.
The underlying current driving these successful cultures is, and has pretty much always been religious beliefs that contain a supernatural overseer whose job it is to instill mutual trust, sometimes through a mutual understanding of the dangers of opposition, keep the populace on the straight and narrow and fiercely committed to correct belief and action. Unfortunately, sometimes beliefs turn in to dogma, intolerance develops and anything not orthodox becomes heretical and conflict rules.
I have to wonder if the cultural upsides of these irrational currents override the downside.