Quote Originally Posted by Dr Kain View Post
If the Engineers wanted us dead to begin with. There is nothing to state they were going to do that. They could have been going to Earth just to check up on things.

My theory is that the sacrifice at the beginning of the movie was actually a prisoner being executed and he ended up creating humans in the process. It could have been that the Engineers were going to wipe out humanity because they spawned from a condemned man, and as such, they themselves are condemned.
The cave paintings and pictograms suggest the Engineers had visited Earth many times since our creation, benignly checking up on us, but then 2000 years ago a ship sets off from a biological weapons facility heading for Earth loaded with, essentially, germ bombs. I agree it wasn't explicitly stated, but I took the inference as they meant us harm (and Shaw certainly drew the same conclusion).

But, it was the writer's stated aim to keep things deliberately vague precisely so we could counjoure up all manner of theories. That's why I liked the movie so much.