Silver Age Beyond
Unbeknownst to most, humanity first reached the stars under the auspices of the First Republic, as god-like Parahumans ruled ‘mere mortals’ beneath them and fought among themselves and other pantheons of early parahumans. During a great conflict lost to time, these early parahumans realized that protracted fighting among themselves could crack the world, and indeed destroy all of the many dimensions connected to it. To that end, having discovered methods of travel throughout their local sectors of space, a brief one-world government run by these “zaibatsu”: god-barons whose religious states replaced, in secret, the sovereignty of the nations of the earth. The zaibatsu pantheons quickly colonized the solar system in search of new sources of wealth and resources, using Primmortal technology found in several ancient sites throughout the earth. Finally at the edge of the solar system they found the jump gate.
This ancient artifact of Primmortal manufacture baffled and awed what would soon be called post-humanity. The posthumans took many years of research to unlock even the most basic secrets of its technology, but its main function was clear: it opened portals to distant star systems. Diligent parahuman god-scientists rekindled the Primmortal power of the first jump drive, an engine installed on a spaceship which could propel the ship through the gate, transporting it instantly into foreign space light years away.
The exodus began. At first, certain zaibatsu pantheons carefully controlled the rekindling and ownership of jump ships and reaped the resources of the new worlds and solar systems. But once parahuman god-anarchists leaked the secret of the technology to all of the other pantheons of Parahumanity, nobody could keep back the vast wave of superpowered people seeking to claim worlds of their own.
Then the unthinkable happened. The jump gate back to Earth, simply inexplicably vanished, stranding most posthumans forever in the stars. Within a short time, the so-called First Republic collapsed in a civil war over ever-expanding territory and diminishing loyalties, as the disparate gods formed new kingdoms in the stars, and the remainder of humanity, without gods to guide it, relegated them to myth, and continued to scrabble in the dust of the fallen gods’ empires, invoking their names in countless holy wars for resources.
As the former god-kings of earth expanded out into the galaxy, so began the great Diaspora.
More information about this can be found by looking at the Timeline of the Known Universe.