Ehrenreich uncovers the origins of communal celebration in human biology and culture. Although sixteenth-century Europeans viewed mass festivities as foreign and "savage," Ehrenreich shows that they were indigenous to the West, from the ancient Greeks' worship of Dionysus to the medieval practice of Christianity as a "danced religion." Ultimately, church officials drove the festivities into the streets, the prelude to widespread reformation: Protestants criminalized carnival, Wahhabist Muslims battled ecstatic Sufism, European colonizers wiped out native dance rites. The elites' fear that such gatherings would undermine social hierarchies was justified: the festive tradition inspired French revolutionary crowds and uprisings from the Caribbean to the American plains. Yet outbreaks of group revelry persist, as Ehrenreich shows, pointing to the 1960s rock-and-roll rebellion and the more recent "carnivalization" of sports.