150,000 BCE

In 150,000 BCE (approx.), The Forerunners rise as the preeminent species in the Milky Way Galaxy by advancing technological discoveries gathered from the remnants left by prior ancient races. Believing themselves responsible for the lives of all those less advanced then they, the Forerunners initiate the Mantle. It is around the same time that humanity is believed by the Forerunners to have "moved their interstellar civilization outward along the galactic arm", possibly to escape Forerunner control.