What happened to the ancients?

Answer 1

A group of ancients known as the "Alterans" arrived in the Milky Way some millions of years ago to leave behind them the struggles they experienced with the fanatical ori sect of their culture. Time passed and eventually The Ancients eventually left the Milky Way to begin a golden Atlantian age in the Pegasus galaxy. The ancients now known as Atlantians built for themselves a magnificant empire in the pegasus galaxy and for a great time they thrived.

However, after some time the Atlantian Empire in Pegasus was slowly depopulized after falling victim to the wraith scourge over a large period of time until all that was left was the city of Atlantis. Without hope, and driven to the brink of extinction the handful of survivors from Atlantis returned to Earth through the stargate to live out the remainder of their lives with the new generation of humans on earth, speculated to be somewhere between 1,000BC - 1,000AD.