Clans, tribes, kingdoms, empires: from the very beginning, there have always been borders.
In that world, thousands of years of human development saw borders divide people into one group after another.
For all kinds of reasons, human groups fought and killed one another over those borders.
Then, one day, the groups remained, but the borders became history.
A cataclysm ravaged the world... The survivors mockingly called the world before them the "Brave New World," and the world before the cataclysm the Old World. The old order had vanished without a trace, so people gave the post-cataclysm world its sarcastic name: the "Brave New World."