One of the often-repeated tales about Saint Patrick is the story about driving the snakes from Ireland. One version tells of his standing upon a hill, using a wooden staff to drive the serpents into the sea and banishing them forever from the shores of Ireland. Another legend says that one old serpent resisted, but the saint overcame it by cunning. He is said to have made a box and invited the reptile to enter. The snake insisted the box was too small, and the discussion became very heated. Finally the snake entered the box to prove he was right, whereupon St Patrick slammed the lid and cast the box into the sea. 

Of course, it is true that there are no snakes in Ireland. In fact, there is no evidence that snakes ever inhabited the island. While many fossilized remains of animals, insects, birds, and fish have been found in Ireland, no one has ever found any fossilized evidence of any serpents on the island in millions of years. 

If one accepts the tales that Saint Patrick is the reason for their absence, one must also marvel that he was able to drive out the snakes' ancestors retroactively, too!