On St. Patrick's Day, most revelers don'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.During this last glacial period, spanning between about 120,000 and 10,000 years ago, both Ireland and the island of Great Britain were far too cold for snakes and other reptiles. After the ice retreated, two land bridges were revealed: one connecting Ireland to Britain, and the other connecting Britain to the rest of Europe.

Around this time, a number of new species, including three different snake species, colonized Britain. But as melting glaciers caused sea levels to rise further, the land link to Ireland became impassable — some 2,000 years before surrounding seas cut off the bridge to Britain.

The prevailing theory is that snakes simply didn’t have enough time to make the last stint of the journey to the Emerald Isle. To this day, the island has only a single native terrestrial reptile: the common or viviparous lizard, which must have arrived sometime in the past 10,000 years, following the end of the ice age.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. #facts #ireland