Thus ended the great series of migrations which, over a space of some nine hundred years, had brought the Somali from their northern deserts into the more fertile regions of the centre and south and finally into the semi-desert plains of northern Kenya. These movements had far-reaching social repercussions. Through contact with the Oromo and the absorption of those Galla who remained behind, and with an added leaven from the earlier Bantu communities, the Digil and Rahanweyn tribes emerged with their distinctive characteristics. From the Bantu they adopted cultivation, and from the Galla temporarily adapted their system of age-grades to their expanding military needs. In much the same way, the Darod who later crossed the Juba briefly assumed the Galla warrior age-grade system, and like the Rahanweyn, later discarded it.

I.M. Lewis, I. M. Lewis, A Modern History of the Som…, loc. 114