What follows is my personal canon for the Space Jockey and the origin of the Xenomorph as seen in Alien, with some influence from Prometheus. Foreseeing their eventual extinction over the next few thousand years, the Space Jockeys send their ships to the furthest reaches of their known galaxy. Each ship is tasked with finding a habitable world to colonize. A prehistoric planet Earth is found by one of these ships. It's determined to be an ideal world for terraforming. There's one problem: the planet is already inhabited by a pre-industrial race of humans. Specimens are collected and taken back to the homeworld for study. There, the Jockeys design their plan. After years of experimentation, the humans' genes are edited into the DNA of a species of parasitic organism, to make the humans a viable host for it. Research ! The union of the two species creates a new one, an Alien xenomorph that will be used as a biological weapon to eliminate the human presence on Earth. D...