for National Geographic News
During St. Patrick's Day next week, most revelers won't remember the patron saint of Ireland for his role as a snake killer.
But legend holds that the Christian missionary rid the slithering reptiles from Ireland's shores as he converted its peoples from paganism during the fifth century A.D.
St. Patrick supposedly chased the snakes into the sea after they began attacking him during a 40-day fast he undertook on top of a hill.
An unlikely tale, perhaps—yet Ireland is unusual for its absence of native snakes.
It's one of only a handful of places worldwide—including New Zealand, Iceland, Greenland, and Antarctica—where Indiana Jones and other snake-averse humans can visit without fear.
But St. Patrick had nothing to do with Ireland's snake-free status, scientists say.
As keeper of natural history at the National Museum of Ireland in Dublin, Nigel Monaghan has trawled through vast collections of fossil and other records of Irish animals. "At no time has there ever been any suggestion of snakes in Ireland, so [there was] nothing for St. Patrick to banish," Monaghan said.
So what did happen?
Most scientists point to the most recent ice age, which kept the island too cold for reptiles until it ended 10,000 years ago. After the ice age, surrounding seas may have kept snakes from colonizing the Emerald Isle.
(Read: "Snakes on a Page: Full Serpent Coverage" [August 14, 2006].)
Once the ice caps and woolly mammoths retreated back northward, snakes returned to northern and western Europe, spreading as far as the Arctic Circle.
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