History of Africa usually governed by an "oba" and an "iwarefa", a council of chiefs who advised the "oba." by the 18th century, the Yoruba city-states formed a loose confederation, with the "Oni" of Ife as the head and Ife as the capital. As time went on, the individual city-states became more powerful with their "obas" assuming more powerful spiritual positions and diluting the authority of the "Oni" of Ife. Rivalry became intense among the city-states. The Oyo Empire rose in the 16th century. The Oyo state had been conquered in 1550 by the kingdom of Nupe, which was in possession of cavalry,
Yoruba people There are three major dialect areas: Northwest, Central, and Southeast. As the North-West Yoruba dialects show more linguistic innovation, combined with the fact that Southeast and Central Yoruba areas generally have older settlements, suggests a later date of immigration for Northwest Yoruba. The area where North-West Yoruba (NWY) is spoken corresponds to the historical Oyo Empire. South-East Yoruba (SEY) was probably associated with the expansion of the Benin Empire after c. 1450. Central Yoruba forms a transitional area in that the lexicon has much in common with NWY, whereas it shares many ethnographical features with SEY. Literary Yoruba, the standard