From the somber Catholic high mass to the painful, often frightening initiation rites of many tribal cultures, every human society practices some form of ritual. But the rituals themselves differ radically – in ways that may be predictable across cultures. Namely, new research shows that complex cultures that depend on agriculture tend to have frequent, repeated rituals that are relatively sedate and calm. Smaller cultures with less agriculture, on the other hand, feature rituals that are less frequent but far more emotionally and physically arousing. Ultimately, these trends may give us a vital clue as to how human culture changes over time.