present lands west of the lower Niger River more than a millennium ago. They eventually became the most urbanized Africans of precolonial times. The Yoruba people eventually formed many kingdoms of various different sizes, each of which was centered on a capital city or town and that was being ruled by a hereditary king known as an oba. Their towns eventually became more and more populated and grew into the present-day cities of Oyo, Ile-Ife, Ilesha, Ibadan, Ilorin, Ijebu-Ode, Ikere-Ekiti, and others. Oyo developed in the medieval and early modern periods into the largest of the Yoruba kingdoms, while Ile-Ife still remained a town of very strong religious significance as the site of the earth's creation according to Yoruba mythology. Oyo and the other kingdoms declined in the late 18th and 19th centuries owing to disputes among minor Yoruba rulers and invasions by the Fon of Dahomey (now Benin) and the Muslim Fulani. The traditional Yoruba kingships still survive, but with only a hint of their former political power. Their chiefs are therefore monarchs and titled individuals, with most of the latter group making up the membership of the Ogboni secret society. Their traditional religion, Ifa, has been recognized by UNESCO as a masterpiece of the oral tradition of Humanity. Nigerian upper class Ever since the country's earliest centralization - under the Nokites at a time contemporaneous to the birth of Jesus Christ - Nigeria has been ruled by a class of titled potentates that are known as chiefs. Led by the Nigerian traditional rulers (i.e. monarchs who have received definite authority from the official government and are recognized by the laws of Nigeria), the chiefs come in various ranks and are of varied kinds - some monarchs are so powerful that they influence political and religious life outside their immediate domains (the Sultan of Sokoto and the Ooni of Ife, for example), while in contrast many local families around the country install their eldest members as titled chiefs in order for them to provide them with what is an essentially titular leadership. Although chiefs have few official powers today, they are widely respected, and prominent monarchs are often courted to endorse politicians during elections in the hopes of them conferring legitimacy to their campaigns by way of doing so. Successful Nigerians, such as businessmen and the said politicians, typically themselves aspire to the holding of chieftaincies, and the monarchs'