I posted this theory on another forum. All right. What if...the hundreds, if not thousands, of eggs found by Kane were former beings, not humans per se, but other space travelers. In Alien, Brett and Dallas are both 'changing' before Ripley puts them out of they're misery. Maybe the SJ's have been leaving these 'invitations' on hundreds of worlds. Maybe they need 'volunteers' for their bioweapons division.