One of Nigeria's three largest ethnic groups, numbering more than 22 million. The many dialects comprising the Yoruba language belong to the Benue-Congo branch of the Niger-Congo family. The Yoruba states, including the Oyo empire, were built in the 11th–16th centuries. Yorubaland remains divided into politically autonomous kingdoms, each centred on a capital city or town and headed by a hereditary king (oba), traditionally considered sacred. Most Yoruba men are farmers, growing yams, corn, and millet as staples; cocoa is a cash crop. Yoruba women control much of the complex market system. Craftsmen work in blacksmithing, weaving, leatherworking, glassmaking, bronze casting, and ivory- and wood-carving. Though some Yoruba are now Christians or Muslims, belief in their traditional religion continues, and it remains alive, too, in the New World countries to which may Yoruba were transported to work as slaves (seeCandomblé; Macumba; Santería; vodun). The Yoruba language has an extensive literature of poetry, short stories, myths, and proverbs.