WHEN signs of a lost world at the bottom of the North Sea first began to appear, no one wanted to believe them. The evidence started to surface a century and a half ago, when fishermen along the Dutch coast widely adopted a technique called beam trawling. They dragged weighted nets across the seafloor and hoisted them up full of sole, plaice, and other bottom fish. But sometimes an enormous tusk would spill out and clatter onto the deck, or the remains of an aurochs, woolly rhino, or other extinct beast. The fishermen were disturbed by these hints that things were not always as they are. What they could not explain, they threw back into the sea…

This article first appeared in National Geographic in December 2012. To continue reading, click here.