When Frogs Fly ...

How We Learned That Frogs Fly

Ninety years ago, scientists were debating the question of animal dispersal. How come there are kangaroos in Australia, and none in southern Africa? Certain frogs show up in warm ponds in one part of the world, but warm ponds a thousand miles away have none. Why?
Scientists in the 1930s hadn't yet come up with the notion of plate tectonics (that continents break up and move, carrying animals with them). Instead, the debate centered on two additional theories. First, that in ice ages, glaciers formed, sea levels dropped, creating land bridges that allowed frogs to hop great distances from one continent to another.