Amateur historian
Gavin Menzies claims in his book
1421: The Year China Discovered America that the southern landmass is indeed the Antarctic coastline and was based on earlier Chinese maps. According to Menzies, Admiral Hong Bao charted the coast over 70 years before Columbus as part of a larger expedition under the famous Chinese explorer and admiral
Zheng He to bring the world under China's tribute system.
Gregory McIntosh and other cartographers and historians who have examined the map in detail believe the resemblance of the coastline to the actual coast of Antarctica to be tenuous. For centuries before the actual discovery of Antarctica, cartographers had been depicting a massive southern landmass on global maps based on the theoretical assumption by some that one must exist, if only to balance the landmass of the North. It was widely believed that South America and, once its northern coastline was discovered,
Australia, must be joined to this land mass, which was thought to be very much bigger than the real Antarctica. This theoretical southern continent, the Great Southern Land or
Terra Australis Incognita (literally Unknown Southern Land), in various configurations, was usually shown on maps until the eighteenth century. An alternate view is that the "Antarctic" coast is simply the eastern coastline of South America skewed to align east-west due to the inaccurate measurement of longitude or to fit it on the page.
[36]
Hapgood suggests that the Antarctic section of the map was copied at an incorrect scale to the rest of the map and resulted in the distortion and enlargement of the continent on several ancient maps. This would explain why there is no waterway between South America and Antarctica. He suggests several points of continuity between the Piri Reis Map and modern maps of the continent below the ice caps. Since
the Antarctic continent was not officially sighted until 1820[37][38] and its full coastline was not known until much later; this claim, if true, would require major revisions to the history of exploration, settlement, evolution, and technological advancements of the time.
[39]
There are many difficulties in the map of South America, including duplication of rivers. Close examination of the coastline supports the alternative theory that the "extra" landmass is simply the South American coast, probably explored in secret by Portuguese navigators, and bent round to fit the parchment. There are features resembling the basins at the mouth of the
Strait of Magellan, and the
Falkland Islands.
