Simplify the following text for a Grade 8 native English-speaking person.
Original: The hypothesis that continents ` drift ' was first put forward by Abraham Ortelius in 1596 and was fully developed by Alfred Wegener in 1912 .
Simplified: The theory was first proposed by Abraham Ortelius in 1596 . It was fully developed by the German geologist and meteorologist Alfred Wegener in 1915 .