Loosely adapted from the novel by French author Pierre Boulle, Planet of the Apes was released at the height of racial and political unrest in America, adding resonance to its story of a NASA astronaut (Charlton Heston) stranded on a planet where superior apes dominate inferior human slaves. The film's final image--in which a horrified Heston realizes the fate of humankind--remains one of the most indelible in all of science fiction cinema.

Beneath the Planet of the Apes (1970) continues the original's distant future scenario, pitting militant apes against mutant humans dwelling in the subterranean ruins of New York City. Its phenomenal success spawned Escape from the Planet of the Apes (1971), in which simian scientists Cornelius and Zira (Roddy McDowall and Kim Hunter, reprising their roles from Planet) travel backward in time, setting the stage for the ape supremacy of the first two films. McDowall returned in Conquest of the Planet of the Apes (1972) as Caesar, the son of Cornelius, leading an ape revolution that bridges the historical gap of the previous films. Battle for the Planet of the Apes (1973) ended the five-film cycle with McDowall again playing the chimpanzee leader Caesar, defeating gorillas and human mutants to establish the hierarchy introduced in the original film.

The Apes films present a classic what-if scenario that hasn't lost a bit of its potency. As if to prove its cultural endurance, the cycle returned to its origins with director Tim Burton's remake of Planet of the Apes--one of the most eagerly awaited films of 2001. --Jeff Shannon