The two main elements in Ethiopia's uniquely rich ethnic cultural heritage are the Cushitic-speaking peoples, traditionally centred in the lowlands, and the Semitic-speaking peoples of the highlands, who derived from a fusion of local Cushitic stock with South Arabian immigrants in the first millennium B.C. The Tigreans and Amharas who have dominated Ethiopian political history from its foundations at Axum, also provide a sturdy peasantry, living typically in dispersed settlements and cultivating cereals (including the idigenous teff) with an ox-drawn plough. In the hotter, lower altitudes south of Addis Ababa where the hand hoe is used, ensete (the false banana) becomes the main crop. The hierarchical Semitic political structure, the conquest state, contrasts sharply with the fierce egalitarianism of the pastoral Cushites - where, as among the Galla, this is associated with an age and generation (gada), or as among the Somali with segmentary lineage organization. The centralized polities of the Kaffa, Sidamo, sedentary Galla and Afar lie between these two extremes. While the national core-culture has for centuries been Christian, the distinction between Christian and Muslim, superimposed upon the earlier Judaic tradition, both reinforces and transcends these ethnic divisions, which were never more acutely felt or politically significant than they are today.