[Destro]

Peri Reis' maps were based on older Greek ones.

[muawiyah]

How do we know they were "Greek"? Certainly there is a suspicion that the maps came from Byzantine sources, but when Columbus received them, Byzantium had been in the hands of the Turks for a number of decades.

Once the Turks took over, their established lines of communication to their linguistic cohorts in the East would have served to provide them with the Chinese discoveries.

One poster noted that the Ming (Mongol) dynastic elements were being kicked out of China during that period by the Manchu. Valuable exploratory maps undoubtedly financed peace and security for more than one Ming noble!