Well, we could start with the opening scene, which conveyed so little meaning that we’ve had at least two radically different interpretations of it in this thread. I thinks yours actually makes more sense EC, but apparently the Word of God has it that it was the DNA seeding thing. But 1) this is never revealed in the movie and 2) isn’t even consistent with what we do see in the movie. We’re told, repeatedly, that the Big Bald Guy DNA is identical to human DNA, which wouldn’t be the case if we were distantly descended from them. What we see happening to the BBG’s body in the opening scene also seems a rather unpleasant way to create other life forms that share your DNA. Humans achieve the same result by having sex. Anyway, this opening scene conveys no clear information other than what the BBGs look like and that this black goo is dangerous and will do something to your DNA, and both these things come up again later and would have carried more punch if they hadn’t been revealed at the very beginning.
We learn in the next scene that early humans knew enough about the Big Bald Guys to create art indicating where they came from and that they are Big and Bald. This means that the BBGs either came to Earth and stayed for a while or at least seeded the planet and then came back to check on things, but nothing is ever said about this. We also apparently learned language from them. Quite a bit of time was spent setting up the idea that the robot had worked backwards to find the common root of all human languages and would be able to communicate with the BBGs, but like so much else in this movie this went nowhere.
I don’t care enough about this movie to detail everything that I felt went wrong after the opening scenes, but here’s a summary: The movie repeatedly gestures at Big Philosophical Ideas but doesn’t follow up on them. The early portion seemed to be building up to something a lot more interesting than what we actually got. Things happen for no apparent reason, or happen and then are forgotten. The supposedly intelligent characters behave like total idiots, spending scene after scene doing dangerous things for no reason, failing to react to events that should seem important, and drawing elaborate conclusions (at least some of which we are apparently supposed to accept as correct) based on very little evidence.