Why did snails replace the ladies and knights of medieval castles?

Abstract

In the Middle Ages, vassals cut down the vast forests than once ruled Europe,  and built stone castles, meant to be inhabited by ladies and defended by knights in armor; these people would inspire the legends and fairy tales that still entertain our childhood. If there was no hill, the castle was built on the plains, but it was surrounded by moats and drawbridges. Centuries passed and cannons rendered the stone walls useless, so most of the castles were abandoned and slowly they have been falling apart, filling the soil with calcium carbonate and cracked stones, the ideal habitat for many land snails. When biologists looked closely at the species in these ruins, the surprise was not only what they found, but also what they did not find.