Origins of Hutu, Tutsi and Twa adults has a high capacity for lactose digestion, a surprisingly high number for an agrarian people, which Mamdani suggests may be the result of centuries of intermarriage with Tutsi. Bethwell Ogot in the 1988 UNESCO "General History" further notes that the number of pastoralists in Rwanda increased sharply around the fifteenth century. Although Luis et al. (2004) in a more general study on bi-allelic markers in many African countries found a statistically significant genetic difference between Tutsi and Hutu, the overall difference were not large. Modern-day genetic studies of the Y-chromosome generally indicate that the Tutsi, like the Hutu, are
Hutu Power public life, complete segregation of Hutus from Tutsis, and complete exclusion of Tutsis from public institutions and public life. Hutu Power ideology reviled Tutsis as outsiders bent on restoring a Tutsi-dominated monarchy, and idealized all things Hutu. The Commandments declared that any form of relationship between Hutus and Tutsi women was forbidden; and that any Hutu who "marries a Tutsi woman", "befriends a Tutsi woman", or "employs a Tutsi woman as a secretary or a concubine" was a traitor to the Hutu people. It denounced Tutsis as dishonest in business whose "only aim is the supremacy of his ethnic group";