Alfred Wegener used fossils to show that continents which are now far apart must once have been joined together in a single landmass.

Key fossil clue

Wegener noticed that identical fossils of the same species appear on continents now separated by wide oceans.

  • He focused on land-dwelling and freshwater organisms that could not have crossed salty, deep oceans on their own, such as the reptile Mesosaurus (found in both South America and Africa) and the plant Glossopteris (found in South America, Africa, India, Antarctica, and Australia).
  • The simplest explanation was that these continents had once been connected, allowing the organisms to live in a continuous range and later be preserved in matching fossil bands.

How this showed movement

From the matching fossil belts, Wegener inferred that the continents were once part of a supercontinent (Pangaea) that later split apart and drifted to their current positions.

  • If continents had always been in their present locations, scientists would have to invent huge “land bridges” across oceans to explain the identical fossils, but those bridges left no convincing geological evidence.
  • Wegener argued that moving continents made much more sense: the fossils matched because the rocks—and therefore the continents carrying them—had once been joined and then moved away from each other.

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