Alfred Wegener used fossil distributions as part of a broader suite of evidence showing that the continents had moved. He argued that identical or closely related fossils found on now-distant landmasses indicated these lands were once connected, allowing species to distribute across a continuous land area before the continents drifted apart oceanically. Key points on how fossils contributed to his case
- Shedding a global pattern: Fossils of the same species, especially plants and some animals, appeared in rock layers of similar ages on continents that are now separated by oceans. Wegener interpreted this as evidence that those landmasses once formed a single, continuous landmass with a terrestrial ecosystem that could harbor the same organisms. This alignment of fossil records across continents was difficult to explain if the continents had always been in their present positions.
- Glimpse of ancient biogeography: The fossil record suggested that land connections existed in the geological past, allowing flora and fauna to spread between regions that are now isolated by sea. The patterns implied a configuration in which organisms could migrate and then become isolated as continents moved, leading to divergent evolution.
- Complementary lines of evidence: Wegener did not rely on fossils alone. He also used the fit of coastlines (like pieces of a jigsaw), matching mountain belts, and correlations in rock types and geological formations across oceans. The fossil evidence was most persuasive when viewed in concert with these other lines of evidence, collectively supporting a model in which continents had once been joined and then separated by plate movement.
Context and limitations
- Wegener proposed Pangaea as the supercontinent that contained all landmasses, with fossil similarities across continents reflecting its breakup. He also suggested that the distribution of fossils could not be explained by land bridges long after the continents had drifted apart, strengthening the argument for continental mobility.
- It’s important to note that while fossil evidence was compelling in Wegener’s time, it was insufficient on its own to establish a mechanism for movement. He faced skepticism partly because he could not identify the physical forces capable of dragging entire continents. The subsequent development of plate tectonics provided the physical mechanism that reconciled Wegener’s fossil and geological correlations with a robust theory of moving plates.
If you’d like, I can pull or summarize specific fossil examples Wegener cited (for instance, plant and animal fossils that appear on now-distant landmasses) and show how they align with the continental configurations he proposed.
