The first time I saw 2001, I misinterpreted the role of the monolith. I thought that it was kind of a herald of the birth of a new species (which is a little bit less than fully correct, but captures the essence of it), but that the new species being born was non-biologic intelligence. In other words, the monolith was there for HAL. And that kill or be killed was the iron rule of the universe, so humanity, represented by Dave Bowman, had to kill of HAL or be supplanted, just as the apes who figured out that a thighbone could crush the shit out of a skull supplanted the bigger and stronger apes at the watering hole.