Stanley Kubrick on "that ending." *SPOILER*

[Nitram]

3. All you have to do is read the novel of the same title Arthur C. Clark's wrote while

the movie was being developed. Earth was on the edge of apocalypse because 21 nations had nuclear weapons in orbit. (The early Homo sapiens who uses the first weapon in history, throws the animal femur into the sky and the scene morphs into the view of a nuclear weapon in orbit). The beings who taught the first humans how to survive (using a monolith) left a tail of clues to lead the human race to their "star gate" wormhole once we had developed space travel. Once the astronaut passes through the wormhole and reaches their star system, they provide a familiar space for him in the form of a hotel room (they'd been monitoring TV shows for years). Using a monolith, they teach him how to evolve to the pure energy form they have achieved, and he rapidly ages. He can choose any form he wants when he transforms into pure energy. He chooses the form of a fetus, symbolizing that man is ready for the next stage of our evolution. He returns to Earth to stop the apocalypse by destroying all nuclear weapons. His next job is to teach humanity what he has learned and save us from ourselves.