Reasoning: The Roman invasion could have been predicted, but wouldn’t have been well supported by evidence—although foreign invasions were certainly a repeated (even cyclic) phenomenon. Of course, the Nemesis hypothesis rests on an unproven root cause of all major extinction events, whereas invasions came from various, known causes...
Perhaps “Get off of Earth before Nemesis sends some more comets our way”
Nemesis: http://en.wikipedia.org/wiki/Nemesis_%28star%29
Reasoning: The Roman invasion could have been predicted, but wouldn’t have been well supported by evidence—although foreign invasions were certainly a repeated (even cyclic) phenomenon. Of course, the Nemesis hypothesis rests on an unproven root cause of all major extinction events, whereas invasions came from various, known causes...