Assuming I'm correctly understanding your question, it was established in the film that the Xenomorph eggs were brought by the Predators. It is unknown whether the Predators directly harvested said eggs, or perhaps acquired them from another race.
Through translation of the pyramid's hieroglyphs, Alexa and Sebastian learn that the Predators have been visiting Earth for thousands of years. It was they who taught early human civilizations how to build pyramids, and were worshiped as gods. Every 100 years they would visit Earth to take part in a rite of passage in which several humans would sacrifice themselves as hosts for the Aliens, creating the "ultimate prey" for the Predators to hunt. If overwhelmed, the Predators would activate a self-destruct device to eliminate the Aliens and themselves.