Alfred Wegener, a German meteorologist and geophysicist, proposed in the early 20th century that continents were not fixed but slowly moved across Earth’s surface. This concept, continental drift, suggested all landmasses were once joined in a single supercontinent he named Pangaea. Initially met with skepticism, Wegener’s hypothesis laid the groundwork for modern plate tectonics.
Wegener’s Groundbreaking Idea
Wegener’s hypothesis asserted that present-day continents were fragments of an ancient supercontinent called Pangaea, meaning “all Earth” in ancient Greek. He suggested Pangaea began to break apart around 300 million years ago, with pieces slowly drifting to their current locations. This idea was radical, as the scientific community believed continents were stationary and lacked a plausible mechanism for their movement. Wegener proposed forces like Earth’s rotation, but these were deemed insufficient. Despite this hurdle, he meticulously gathered diverse lines of evidence, including the remarkable fit of continent coastlines.
Fossil Evidence Across Continents
The distribution of ancient fossils provided compelling support for Wegener’s continental drift hypothesis. Identical fossilized remains of terrestrial or freshwater plants and animals were discovered on continents now separated by vast oceans. These organisms could not have traversed immense saltwater barriers. Their presence across widely separated continents strongly suggested these landmasses were once connected, forming continuous habitats.
Such fossil distributions argued against independent evolution or repeated long-distance oceanic crossings. The shared fossil record indicated a unified landmass providing a continuous environment. When continents are reassembled according to Wegener’s Pangaea model, fossil distribution forms coherent, unbroken patterns. This congruence became significant evidence for a supercontinent’s former existence.
Unlocking Ancient Landscapes
Specific fossil discoveries offered tangible proof for Pangaea. The freshwater reptile Mesosaurus, from the Early Permian period, has fossils found exclusively in southern Africa and eastern South America. As Mesosaurus was ill-equipped to swim vast oceans, this indicates these two continents must have been joined.
Another key piece of evidence came from Glossopteris, a woody, seed-bearing fern or tree from the Permian period. Fossils are found across South America, Africa, India, Australia, and Antarctica. Its heavy seeds could not have been dispersed across oceans by wind or water currents, reinforcing that these landmasses were once connected.
Further support emerged from the land-dwelling reptiles Lystrosaurus and Cynognathus. Lystrosaurus, a herbivorous mammal-like reptile from the Early Triassic, has fossils found in Africa, India, and Antarctica. Cynognathus, another mammal-like reptile from the early to mid-Triassic, is found in South Africa and South America. As terrestrial animals incapable of long-distance swimming, their widespread fossil distribution strongly suggested these continents were once part of a continuous landmass.