Theory: Since the minions were a species which evolved during the time of the dinosaurs, it's not impossible to assume there were millions of them around the globe. However, when the world wars started both Stalin and Hitler attracted minions to both sides of the eastern front. The reason why the eastern front was so bloody was because of the amount of minions killing each other to determine which side is more evil and worth their service. This minion civil war killed nearly every minion making them almost entirely extinct accept for the minions in the ice cave. Some evidence in the movies to support that there were minions in the world is how little people react to them in public and treat them like regular people.