why,why, why?

Rating: 7/10 (13 June 2012)

hello, film was good, but it would be even great if there wasn't that many illogical moments in the whole storyline. few questions that I could not answer ( if anyone can please do :) ) 1. how come, after leaving just the DNA and without coming again, different civilizations draw maps of where the engineers are? 2.why after killing the baby monster in that special operations room, suddenly ( few hours later ) it went big and capable of killing? 3. Why a robot that only helps people will infect a human? 4. why a robot or his master will want to see a hybrid between an unknown creature and a human? 5. if the creators wants to kill us, why don't they just come to earth and do it, instead of waiting for us to come??? 6. What exactly the hologram recordings showed? many engineers run away from something, and only few succeed, and then suddenly they decided to go and have a nap???
they are many more, but I'll stop here. Pity that otherwise great idea for storyline, awesome visuals and great actors, were a bit wasted. with a bit more brains, this film could be one of the greatest sci-fi in the past decade.
Please answer me smart people if you think I've missed something... :)
Cheers,