The idea that the continents appear to have been joined based on their shapes is not new. In fact. this idea first appeared in the writings of Sir Francis Bacon in 1620. The resulting hypothesis from this observation is rather straightforward: the shapes of the continents fit together because they were once connected and have since broken apart and moved. This hypothesis is discussing a historical event in the past and cannot be directly tested without a time machine. Therefore, geoscientists reframed the hypothesis by assuming the continents used to be connected and asking what other patterns we would expect to find. This is exactly how the turn of the century earth scientists (such as Alfred Wegener) addressed this important scientific question.
Wegener compiled rock types, fossil occurrences, and environmental indicators within the rock record on different continents (focusing on Africa and South America) that appear to have been joined in the past and found remarkable similarities. Other scientists followed suit and the scientific community was able to compile an extensive dataset that indicated that the continents were linked in the past in a supercontinent called Pangaea (coined by Alfred Wegener) and have shifted to their current position over time. Dating these rocks using the methods discussed in chapter one allowed the scientists to better understand the rate of motion, which has assisted in trying to determine the mechanisms that drive plate tectonics.