Approximately 10,000 years ago, the Supreme System Lord of the Goa'uld, Ra, transplanted a number of ancient Egyptian people from Egypt, Earth to Abydos via the Stargate in order to use them as slave labour in mining Naquadah. About 5,000 years later, Ra's slaves on Earth rebelled and buried the Stargate. It was around this time that Ra banned all written language on Abydos, so that they wouldn't learn what happened on Earth and do the same thing on Abydos. After all this time, they still worshipped Ra as a god. (Stargate)