Somewhere in the Universe, there must be something better than man!
Why it is hard sci-fi
A 1968 film built around a relativistic spaceflight premise that holds up. The crew launch from Earth, accelerate to near light speed, and crash on a planet where time-dilated travel has carried them several thousand years into the future. The ape society is the set piece, but the science backing the trip is correct enough that it survives the films deliberate framing twist.
Science inside it
Special relativity and time dilation under near-light-speed travel, the consequences of a long-haul mission with no realistic return, and the slow evolutionary scenarios that produce the films inverted hierarchy. Heston s crew is asleep for the trip, which is consistent with the period s thinking about long-duration spaceflight.
Spoiler alert
The planet is Earth in the far future. The shoreline statue confirms it. The crew never left the home system in any meaningful sense. They left the home century. The films closing image makes the time-dilation premise the punch line.