My explanation of the entire movie

I'll start off with David. David is a creation of man. Man has a very clear perception of what David should be, his purpose and what should be expected of him. We build machines to aid us in a wide spectrum of tasks. We build with the notion that no machine should ever surpass us, present any danger to us or compete with us. We build cautiously and as you can imagine in the event of possible danger we will not hesitate for a single moment to destroy our creation(s). I think we can all agree on this as this is the plain truth which applies to us today and which will continue to apply in the future when David becomes a reality. In the case of David, the movie clearly emphasizes the fact that while he can surpass his creators in a variety of tasks he is designed to exhibit his differences in a minimum way as to create comfort for his creators. The movie also states that David has no soul and that no matter how hard he tries he will never become us. This also hints at the fact that should David ever defy his creators he will quickly become a threat to be dealt with. This is expected and I think we can all agree on this as well. Moving on to the engineers. They create just like we do. Why? Same exact reasons as ours - to build useful resources perhaps, to experiment to see how far they can evolve, to question their own origins and to possibly surpass their creators and become the ultimate creators themselves. The movie starts with a sacrifice. The habitat is formed and the sacrifice is made. The black goo is a production factory if you will. An accelerator, a catalyst, a glue if you will. Now back to our creations. What happens you supply the assembly line with parts? They get assembled into something - first other parts which then go to form other parts and in the end the final product. What happens if you place the finished product onto the same assembly line? It gets destroyed simply because the assembly line is designed to start of with smaller building blocks. This is what happens to the engineer in the opening scene. He gets disassembled by the same process which is designed to form the building blocks of new life. As time goes by, the engineers are happy with their creation. They revisit earth at various time in history to observe, perhaps collect even. As proven by pictograms. At the same time they move through the endless galaxies and continue to create. Edit: the above proves that the engineers were fine with us and having had multiple opportunities to wipe us out (with the goo or any other weapon) they clearly didn't. The goo is an extremely potent bio-tech product and is kept at several remote storage facilities that house the necessary components as well as terraforming and goo delivery vehicles. As a testament to their achievement the engineers even have statues signifying that they rise above all and life is their creation. Think science over religion. Science says there is no god and that we are the makers of our own destiny. At some point there is a breach in one of the storage units and the engineers are exposed to the consequences of an experiment gone wrong. They are all presumed dead and the planet quarantined. Our group arrives at the quarantined planet. Everyone has their own agenda. David wants a soul, he wants to be the same as us, wants to come as close as possible to being a creator or engineer as us and now as the aliens. This is nothing different from what we do every single day and what the engineers do. The creation strives to become the creator. David purposely infects one of his creators and watches. The amount is small yet it starts the process of decomposition. Problem is the process is slower than what it meant to be so the assembly line is actually assembling while it is disassembling. Life emerged from the sea. Creation of the first building blocks was designed this way. Thus we get the squid-looking thing. It's a predator, naturally, no need to explain why. Yet it isn't what it was supposed to because the process was all wrong. Back to the engineers. While all were presumed dead, one survived as he simply wasn't awoken with the reset for some reason. There could be many and it really does not matter why, that's slicing things too thin. So we now have a bunch of humans awakening this one engineer. Now this is berry important to understand: imagine yourself being woken up, stretching your muscles, getting your bearings straight and then realizing that you are surrounded by your own creations, now much more advanced having reached you where you never expected them to be. You are startled. All of a sudden one of them speaks in your language, the language you never taught any of your creations. Then on top of things you realize that this speaking being is not your creation at all but the creation of your creation and one that is quite possibly more advanced than any "life" form you've created. What now? Panic. Fear. The overwhelming need to eradicate this clear and present danger. You attack the most dangerous entity first and the proceed to destroy the rest. To you they are not your kind, they don't have your soul and they mean nothing. They are your machines. How dare they bring themselves so close to you, how dare they enter your realm. How many of them are out there? How far had they reached? You need to immediately alert your home and proceed to their home planet to stop this abdomination. This is exactly what the engineer does. You would have done the same. Is is by accident that the engineer becomes the victim of a hybrid product of his own creation - the very thing he was afraid of in the first place. The rest is history.