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,
Nigeria of Igbo culture. Nri and Aguleri, where the Igbo creation myth originates, are in the territory of the Umeuri clan. Members of the clan trace their lineages back to the patriarchal king-figure Eri. In West Africa, the oldest bronzes made using the lost-wax process were from Igbo-Ukwu, a city under Nri influence. The Yoruba kingdoms of Ife and Oyo in southwestern Nigeria became prominent in the 12th and 14th centuries, respectively. The oldest signs of human settlement at Ife's current site date back to the 9th century, and its material culture includes terracotta and bronze figures. Oyo, at its territorial