Darwin believed one of the more popular explanations of his time: expanding Earth theory. Basically, the planet was like an expanding dough ball. It decently explained why things looked like they fit together. Darwin even went out to Patagonia to investigate some cliffs, and basically “confirmed” the theory.
So Darwin was trying to explain how creatures with common lineage appeared both sides of an ocean. He “proved” that the land masses were once joined. He didn’t really care so much about “how” they were joined, but it was vital to his theory of evolution that they were.
Darwin believed one of the more popular explanations of his time: expanding Earth theory. Basically, the planet was like an expanding dough ball. It decently explained why things looked like they fit together. Darwin even went out to Patagonia to investigate some cliffs, and basically “confirmed” the theory.
So Darwin was trying to explain how creatures with common lineage appeared both sides of an ocean. He “proved” that the land masses were once joined. He didn’t really care so much about “how” they were joined, but it was vital to his theory of evolution that they were.