Xan Fielding’s translation of La Planète des singes was known in some quarters by another title, Monkey Planet (1964), a phrase lacking the dignity Pierre Boulle had conferred on his simian civilization. The dignity of a simian society that, whatever its many ineradicable imperfections, has eliminated war and the serious consequences of racial and class conflicts is somehow associated less with the prank-suggestive adjective “monkey” than with the more substantial noun “apes.” It is dignity, or the quality of worth, with which the story is largely concerned.

The story’s frame is the discovery of a manuscript inside a bottle that is floating in space. Its retrievers are Jinn and Phyllis, a wealthy couple enjoying a holiday as they cruise in their private spaceship. Jinn, who knows the Earth language in which the manuscript is written, reads it to Phyllis, after which both react to it incredulously.

The manuscript contains the account by a French journalist, Ulysse Mérou, of his two-year stay on an Earth-like planet on which the Earth’s situation of civilized humans and wild apes has been reversed. Humans lack intelligence and speech, live naked in the wild, and are preyed on by apes, who use them as objects of study in physiological research. Ulysse and his companions, scientist Professor Antelle and physician Arthur Levain, are captured by gorillas after landing on the planet, which they christen Soror because it is like a sister to Earth. Levain is killed by the hunters, and Professor Antelle reverts, in extended captivity, to the brute animal state of Soror’s humans. Ulysse manages to survive by ingratiating himself with two chimpanzee scientists, Cornelius and his fiancée, Zira. He learns the simian language, wins the respect of the scientific community, and is allowed finally to wear clothing, as do the planet’s apes, but not its humans.

The villain is an orangutan named Zaius, who contests the research of Cornelius and Zira and plots the liquidation of Ulysse. The cohabitation of Ulysse with a beautiful but primitive human female, whom he names Nova, results in the birth of their son, Sirius. The family escapes from Zaius and the planet with the help of Cornelius and Zira. Ulysse takes Nova and their child to Earth, which, owing to the relativistic variations of space-time, is now seven hundred years older than when he left it less than a decade before. Landing in Paris, Ulysse discovers that Earth’s evolutionary processes have turned it, like Soror, into a planet of apes. He escapes with his family, writes his account, and casts it adrift in the bottle picked up by Jinn and Phyllis, who, the reader learns, are chimpanzees.

In Planet of the Apes, two space travelers, Jinn and Phyllis, discover a manuscript in a bottle. The manuscript’s narrator, a journalist named Ulyssé Merou, tells of accompanying Professor Antelle, his disciple Arthur Levain, and a chimpanzee named Hector on a journey to the star Betelgeuse. Discovering a habitable planet, they leave their spaceship in orbit, taking a launch to the planet’s surface.

They christen the planet “Soror, because of its resemblance to our Earth.” The first human they see, who “possessed the most perfect body that could be conceived on earth,” they name Nova. Nova’s bodily perfection is matched by her apparent weakness of mind. Human voices frighten her, and she is agitated when the Earthlings don clothes. When Nova kills Hector, the Earthlings begin to suspect that all is not well. These suspicions are exacerbated when they meet more humans: All, like Nova, are naked and nonverbal. Before the Earthlings act, however, the indigenous humans destroy their clothes, take their weapons, and disable their launch. Merou, Antelle, and Levain, therefore are physically indistinguishable from the native humans when they encounter one of the intelligent species on the planet: a band of gorillas on horseback who hunt, shoot, and capture humans. Professor Antelle is lost, Levain is killed, and Merou is captured in a net and taken to the city.

There, Merou is placed in an individual cage, as are several other captives, including Nova. Merou quickly realizes that the apes are conducting psychological experiments on the humans. He speaks French to the two gorilla guards, Zoram and Zanam. Although they do not understand his language, they bring Zira, a chimpanzee, to see him. Merou speaks French to her. Zira summons Dr. Zaius, the orangutan who runs the institute, to see Merou.

Zaius is less impressed, eventually ordering Nova thrown into Merou’s cage. The intent—to observe mating rituals—could not be clearer. Merou, “a man created in the image of God,” finds himself manipulated into doing a “mating dance” with Nova.

Zaius intends to present Merou at a scientific conference as a curious, but not sentient, human. With coaching from Zira and her fiancé, Cornelius, an anthropologist, Merou learns the language of the apes. He gives a speech to the conference relating his origins and accomplishments, after which he immediately collapses. Merou wakes to find himself installed in an apartment. He joins the chimpanzee research team and teaches some of the humans the rudiments of speech.

While he was less successful linguistically with Nova, she has become pregnant, a matter that Zira goes to great length to keep from becoming generally known. The knowledge that a human can talk and rumors that he is teaching other humans to speak is spreading fear among the general ape population. Meanwhile, Cornelius, conducting an archaeological dig in the southern hemisphere, uncovers relics of an advanced culture, including a talking human doll. The conclusion is inevitable: Human civilization preceded ape civilization on the planet.

This discovery increases the danger to Merou and his newborn son. With assistance from Zira and Cornelius, Merou, Nova, and their child are substituted as “animals” on an experimental spaceflight and rendezvous with the ship that brought Merou to the planet. Merou pilots the original ship back to Earth, while the chimpanzees report their experimental flight destroyed. While Merou expects Earth to have changed since his departure, the magnitude of that change becomes apparent when they arrive—and are greeted by a uniformed gorilla. They hastily return to their ship, destined to wander the galaxy in search of intelligent human life.

In the denouement, Jinn and Phyllis, having read the manuscript, are amused by what they perceive to be a work of fiction. The two chimpanzees continue their pleasure jaunt, content in their superiority.