"As a rule, the populations of African states are multitribal. (Congo is inhabited by 300 tribes, Nigeria by 250), whereas only one group inhabits Rwanda, the Banyarwanda, a single nation divided into three castes: the Tutsi cattle owners (14 percent of the population), the Hutu farmers (85 percent), and the Twa labourers and servants (1 percent).
Their greatest, and really sole wealth, was cattle: the zebu cows, a breed characterised by long, beautiful, swordlike horns. The cow was the measure of everything: wealth, prestige, power. The more cattle one had, the richer one was; the richer one was, the more power one had. The king owned the most cattle, and his herds were under special protection.
“The Tutsi?” I often heard in Rwanda. “The Tutsi sits on the threshold of his house and watches the herds grazing on the mountainside. The sight fills him with pride and happiness.” The Hutus, on the other hand, constitute the much more numerous and subordinate caste of farmers. The relations between the Tutsis and the Hutus were authentically feudal - the Tutsi was the lord, the Hutu his vassal.
The Hutus lived by cultivating land. They gave a portion of their harvest to their master in exchange for protection and the use of a cow (the Tutsi had a monopoly on cattle; the Hutus could only lease them). Everything according to the feudal order - the dependence, the customs, the exploitation.
from The Shadow of the Sun - my African Life