So the Mayans were right.
Just, not exactly in the way that everyone was predicting. There were no flaming meteors, no gods returning, no massive caldera eruptions, no catastrophic earthquakes… No, it was simply humanity’s time as the dominant species had run out. There simply were too many of them. Late in the year of 2011, skirmishes began to break out between the usual enemies. Then, all too quickly, it became another World War.
Except, those who were lucky enough to have survived (or were they really that lucky?) didn’t refer to it as World War III. Most just considered it to be The End.