Hapgood concluded that these ancient mapmakers were in some ways much more advanced in mapmaking than any people prior to the 18th century. It appears they mapped all the continents. The Americas were mapped thousands of years before Columbus. Antarctica was mapped when its coasts were free of ice. There is evidence that these people must have lived when the Ice Age had not yet ended in the Northern Hemisphere and when Alaska was still connected with Siberia by the Pleistocene, Ice Age ‘land bridge’.