We see the monkeys (humans) struggling and on the verge of dieing off. The obelisk appears and suddenly the apes discover tools. (the obelisk is placed there be a superior race or being) skip forward 3 million years. Think of it as a 3 million year evolution timer, when your apes can get to the moon they are ready to make contact with. Man goes to the moon and finds another obelisk. When it is dug up a loud shriek is heard, it is a signal that is directed out toward Jupiter.
The mount a mission to find where that signal was sent to. and go to Jupiter where a third obelisk is found. It is a portal of some kind. Bowman goes in and is transported somewhere. He spends some time in what look like a hotel room where he is transformed, and returns to earth as a baby. But as a baby of the advnaced beings. Sent back to earth to watch over it.
In 2010 Bowman was the baby
Did you know that Arthur C Clarke before he died made 3001 where Dave Bowman come back to earth 1,000 year later he was found some century old NASA talk about how he save the earth from Europa or something like that
It was good book