Initially the shape of the continents— which appear to fit together like a jigsaw puzzle — suggested the possibility. Matching geologic formations and ancient fossil groups in eastern Brazil and South Western Africa have further support to this theory.
Also, the discovery of the sea floor spreading, mid ocean trenches, and plate margins and subduction zones provides a firm foundation for the theory. With the advent of GPS astrologers where we could precisely measure the annual spread, the theory was confirmed in real time.