Though it was thought that the Tollan were brought to Tollan by use of the Stargate, and indeed some believed it was by the Ancients themselves, this was not in fact the case. The truth was lost to even their own histories, and so even the Tollan themselves did not know they were originally the Mayans of Earth. They were transported to Tollan through the crystal skull network by the Omeyocans, as their territory on Earth was being invaded by the Goa'uld-controlled Aztecs. Settling on the planet, the Tollan soon forgot about their Omeyocan saviors and the crystal skulls themselves. (SG1: "City of the Gods")