As joint members of the Eastern Cushitic language family the ancestors of the Somalis and Oromo are believed to have originally inhabited the highlands adjacent to the lake region of Ethiopia. Research in modern historical linguistics indicates that from this cradle land, the proto-Somali thrust to the northeast, occupying part of the Horn by about 1000 AD or earlier (see, e.g., H. S. Lewis, 'The Origins of the Galla and Somali', Journal of African History, 7, 1, 1966; B. Heine, 'The Sam Languages. A History of Rendille, Boni and Somali', Afroasiatic Linguistics, 6, 2, 1978; U. Braukamper, 'Oromo Country of Origin: A Reconsideration of Hypotheses' in G. Goldberg and B. Podolsky (eds.), Ethiopian Studies, Rotterdam, 1981, pp. 25–40). Thus the north-south migrations of individual Somali clans discussed here appear to represent a secondary sequence of population movement following the introduction of Islam.

I.M. Lewis, I. M. Lewis, A Modern History of the Som…, loc. 725