Fellow scientists ridiculed Alfred Wegener's theory of continental drift because he did not have a mechanism to explain how such a thing could happen, and because it went against currently accepted theories.
In 1911 Wegener, a German scientist, came across a paper that referred to fossils of animals and of plants that were identical to each other. The fact that these fossils were on opposite sides of the Atlantic Ocean made him search out and find more examples. The accepted theory at the time was that land bridges had once connected the continents, and that that was how these fossils could be found thousands of miles apart, with an ocean in between. Wegener also found similar land features, such as mountain ranges, that fit together when corresponding areas of the continents were matched up in a way similar to a jigsaw puzzle. The idea Wegener proposed for how the continents moved turned out to be incorrect--he thought the continents traveled through the Earth's crust. Plate tectonic theory eventually proved Wegener to be correct in his general theory--that the continents had indeed once been one large continent--but that they and the ocean floor were part of plates on the Earth's crust that moved relative to each other over the course of hundreds of millions of years.