Zardoz

Zed, one of a carefully bred race of supervisors, the Exterminators, who oversee the agricultural labor of the neanderthal Brutals, since in 2293, with most of the Earth's surface off-limits as a polluted Outlands, industrial society has been abandoned. All worship Zardoz, a huge flying stone head who makes periodic visits to Earth to pick up grain consignments and issue bizarre statements involving the male anatomy through the voice of Arthur Frayn. An increasingly skeptical Zed decides to stow away inside the head, which deposits him in the Vortex, a commune of scientists and intellectuals who are ruled by the ever-youthful and asexual Eternals. They capture Zed, allowing geneticist May to use him as a research subject for a limited period, but he begins to arouse more than scientific curiosity in the commune's supposedly nonsexual female population...