land bridge

A land bridge forms a link between two continents across which plants and animals may move to colonize a new habitat. This bridge may stand in the present—such as the Isthmus of Panama—or it may have existed in the past before it was lost to continental drift or a change in sea level. Anthropologists and biologists who study modern distributions of flora and fauna take special note of these places that have served as migratory routes for the dispersal of terrestrial, landlocked animals, recognizing, for instance, the possibility that humans discovered America many centuries ahead of Columbus by walking across land that now lies beneath the Bering Strait.

Barbara Kingsolver