For me I have always felt the message in 2001 is that aliens came to the earth when monkeys ruled and they adapted our dna to make us into the being that we are today, homo sapiens. The monolith epitomized the unfathomable technology of the superior race which then laid buried on another planet waiting for mankind to reach the level of sophistication and technology to find it and start fulfilling our true destiny as we move out across the universe seeding life as we go. Prometheus plays with the same idea.
But I used to smoke a lot of shit back in the day!