The film masterfully sets up a decoy premise: Taylor firmly believes he has landed on a distant, alien planet orbiting a star in the constellation of Orion. However, the devastating final shot reveals the half-buried remains of the Statue of Liberty, proving he has been on Earth the entire time—thousands of years in the future after a nuclear apocalypse.
This twist recontextualizes the entire film. The "Forbidden Zone" is actually a radioactive wasteland left over from human warfare. The evolutionary regression of humans into mute animals was caused by a combination of nuclear fallout and apes rising to dominance. Dr. Zaius's villainy is also reframed: he was not merely an ignorant religious zealot, but a custodian of a terrible truth. He knew exactly what humans were capable of, and his cruel subjugation of Taylor was a desperate attempt to prevent mankind from regaining power and destroying the planet a second time.