Humanity is shown united under a constitutional monarchy; while there are princes and princesses, decisions appear to be made by democratic vote.
When the Golden Tribe sent out the call, Three Tribes answered the call which are the Bronze Tribe, Silver Tribe, and the Heroic Tribe. Before they left for another universe a fourth answered their call. It was a human ship in which the Golden Tribe only found one survivor onboard the ship and bestowed the name the Iron Tribe on his race.
Soon after the Golden Tribe left the Silver and Bronze Tribes attacked Earth. Due to this, the Iron Tribe was forced to relocate to the furthest reaches of the universe.