Humans on other planets

I was just thinking: what if the crew of the Prometheus discover evidence of humans on other planets? Why wouldn't the Engineers create multiple worlds with humans on them? There isn't really any reason why they wouldn't. I think it would be a disturbing thought to know that there are countless strands of humans across the cosmos being manipulated by a highly advanced civilization. I wouldn't be surprised if there were any weird plot twists like this in the movie. The mythology of this film is likely going to be quite a bit grander than what we are currently led to believe.