Through several decades, plenty of people noticed the strange jigsaw-piece similarity between the east coast of South America and the west coast of Africa, but it wasn't until 1915 that someone pointed out it could be more than a coincidence. Alfred Wegener's insightful observation led to our theory of plate tectonics and continental drift; it is an observation that, at a stroke, did away with the"stamp-collecting" nature of geologic science and gave it a unifying theory that opened up billions of years of Earth's history for inspection.
