June 13, 2012 First of all it is never directly said that the space jockeys/engineers created us intenionally.. its more implied that the broken down dna evovled overtime.
The film prometheus gives hints to the creation of the xenomorph we see in the Alien franchise. When the humans first come upon the room of ampules, there is a scene in which it shows you a close up of a step being taken, follow by tiny worms when the foot is removed. insignifcant? highly unlikely as we see not much further on those same little worms in goo.
later on we see snake/worm like creatures. these creatures closely resemble a chest burster. they also have the acid properties later found in the xenomorphs.
We also see one of these creatures enter the body of Fifield who later comes back as a mutated/evolved form.
we also later see a squid like creature which would become somewhat of a precursor to a facehugger which attaches itself to the Engineer. and finally at the end we see the begins of what a xenomorph will be.
so those were the clues
so who created the xenomorph...... based on those clues... the creature that bursts out of the engineers chest would no doubt eventually encounted the snake/worm like creatures, who are faster and more agile... and just like it entered the body of Hifield, it would also enter the pre-xenomorph creature not killing it, but mutating and evolving it.. this would explain how the eventual xenomorph creature is agile and fast aswell as explain how its blood is acidic and how its head becomes more elongated, it would also explain the reason why the facehuggers and chestbursters also look like a combination of the two precursor creatures we see in prometheus aswell as, why the xenomorph lays eggs, as the snake/worm like creatures would have laid eggs. this is possibly why evertime a facehugger latches on to a certain host, the resulting alien that eventuates from the victim takes on traits of the host. its a result of the initial reaction we see in prometheus caused by the goo
this whole theory could also suggest how a possible sequel and possible link to the Alien movie could be done, as we see at the end of Prometheus Shaw travels to the Engineer homeplanet... Based on the hostility shown by the Engineer that was woken from stasis we can assume Shaw would be killed when she reached their planet and The Engineers would likely return to LV-223 to determine the events that took place. they would also discover the pre-xenomorph which has now evolved into the xenomorph we all know. True to form one would find an egg, the egg would hatch, an engineer would get face hugged, an alien would result and reign chaos. The Engineers would then collect the eggs, put them into stasis, and fight off all remaining xenomorphs, and nuke the base to make certain they are all wiped out. we could assume only one engineer survives, jumps into the pilot seat to plot a course for home, feels his chest sarting to hurt, sets off the distress signal and then crash lands on LV-426 where 30 years later in the year 2122 the nostromo picks up the signal and the events of Alien start.
