1 Quarantine Officer: So why are you trying to smuggle snakes into Scotland?
2 Steve: I thought I'd bring some to show how bewdiful they are, since I heard you poor folks don't have any over here.
3 Quarantine Officer: That's Ireland!
3 Steve: Same thing, isn't it?
4 Quarantine Officer: Arrest this New Zealander!
4 Steve: Crikey! I'm Australian!
4 Quarantine Officer: Same thing!

Most of us know the legend of St Patrick driving the snakes out of Ireland. The fact is, there are no snakes native to Ireland. Why is this so?

It turns out that as recently as about 15,000 years ago Ireland was covered by ice, during the last ice age. Even if there were any snakes there in earlier times, there certainly weren't during the big freeze. And when the ice melted, it left Ireland separated by a broad, deep, and cold channel of sea from the nearest refuge of scaly serpents, Great Britain.

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2018-12-23 Rerun commentary: The second link above disappeared and I had to replace it with a copy from archive.org.

But I also found some other stuff about the last ice age in Ireland, not all of it consistent on the exact dates:

• Prehistoric Ireland on Wikipedia
• Ireland in the Ice Age
• "Ireland's ice age uncovered" from The Ireland Times