Charles Hapgood was a very intelligent man, who happened to discover a great many remarkable things, yet very few people have heard of him. He was born in 1904, and graduated from Harvard University. He became a professor of Anthropolgy at Springfield College, Massachusetts.
He published a number of books in his life, most famously:
Maps of the Ancient Sea Kings; Path of the Pole (3 editions); Earth's shifting crust.
Many ignored what he had discovered or refused to believe it. He had actually worked out, with extensive evidence, that:
a) The positions of the poles change about once every 10,000-30,000 years.
b) He dicovered the significance of several ancient maps, especially the Piri Re'is map, which were shown with Antarctica drawn as a continent, not with ice but as a continent like Europe, covered in grass. He therefore made the assumption that this map had in fact been made from earlier maps (with other evidence), and because of his proof over the shifting poles, the map can be dated at around 11,000BC.