Seeking to discover trade routes to India, the Portuguese explorer Fernão do Pó, sighted the island of Bioko in 1472. He named the island Formosa ("Beautiful"), but it commonly was referred to as "Fernando Po". Within two years, the islands of Annobón, Príncipe, and São Tomé were also charted by the Portuguese. Based on their explorations, by 1480 Portugal had claimed the African coastline between Arguin, in present day Mauritania, and , in present day Gabon, as well as the islands of Cape Verde and in the Gulf of Guinea. In 1521, the Ordinances of Manuel I (), established that subjects were those born in Portuguese territory and that those leaving the territory without permission of the sovereign was grounds for denaturalization. In 1603, the () established that Portuguese subjects were children born on the Iberian Peninsula or adjacent islands, Brazil, or to an official in service to the crown in the Portuguese possessions of Africa or Asia, whose father was a native of Portugal, or whose mother was a native of Portugal and was married to a foreigner who had established domicile in Portugal for a minimum of ten years. Those who were not in service to the crown in the colonies (except Brazil) were not considered to be Portuguese. A child could not derive nationality directly from its mother unless it was illegitimate.
