The first inhabitants of the region that is now Equatorial Guinea are believed to have been Pygmies. Bantu migrations between the 17th and 19th centuries brought the coastal tribes and, subsequently, members of the Fang tribes from today’s territories of Cameroon and Gabon. The Portuguese explorer, Fernando Po (Fernao do Poo), while seeking a route to India, is credited to have discovered the island of Bioko in 1471. The Portuguese retained control over it until 1778, when the island, adjacent islets and commercial rights to the mainland between the Niger and Ogoue Rivers were ceded to Spain in exchange for territory in South America (Treaty of Pardo). From 1827 to 1843, Britain established a base on the island to combat the slave trade. The Treaty of Paris settled conflicting claims to the mainland in 1900, and periodically, mainland territories were united administratively under Spanish rule. Equatorial Guinea gained independence in 1968 after 190 years of Spanish rule. In 1968, Equatorial Guinea had one of the highest per capita incomes in Africa. The Spanish helped Equatorial Guinea achieve one of the continent's highest literacy rates and developed a network of health care facilities before they departed.