The Yoruba are a linguistic community rather than a single ethnic unit. History, language, and membership in the modern nation-state, however, have led to their identity as ethnic groups. Yorubaland takes in most of southwestern Nigeria and the peoples directly west of the Nigerian border in the independent country of Benin. In Nigeria alone, Yorubaland included 20 million to 30 million people in 1990 (i.e., about double the 1963 census figures).
Each of its subunits was originally a small to medium-sized state whose major town provided the name of the subgrouping. Over time seven subareas--Oyo, Kabba, Ekiti, Egba, Ife, Ondo, and Ijebu--became separate hegemonies that differentiated culturally and competed for dominance in Yorubaland. Early nineteenth-century travelers noted that northern Oyo people had difficulty understanding the southern Ijebu, and these dialect differences remained in 1990. The language is that of the Kwa group of the Niger-Congo family, related to the Idoma and Igala of the southern grouping of middle belt chieftaincies south of the Benue River. The population has expanded in a generally westerly and southwesterly direction over the past several centuries. In the twentieth century, this migration brought Yoruba into countries to the west and northwest as far as northern Ghana.