Planet of the Apes (1968)

Complex sociological themes run through this science-fiction classic, about three astronauts marooned on a futuristic planet where apes rule and humans are slaves... The stunned trio discovers that these highly intellectual simians can both walk upright and talk. They have even established a class system and a political structure. The astronauts suddenly find themselves part of a devalued species, trapped and imprisoned by the apes. But one, Taylor, manages to break out and, aided by a pair of compassionate chimps, makes his escape to an uninhabited section of land. However, during the trek Taylor makes a startling, unsettling discovery about the planet -- and realizes he's come full circle.