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
Rwandan genocide the capital and the country. An estimated 2,000,000 Rwandans, mostly Hutu, were displaced and became refugees. The genocide was planned by members of the core Hutu political elite, many of whom occupied positions at top levels of the national government. Perpetrators came from the Rwandan army, the Gendarmerie, and government-backed militias including the "Interahamwe" and "Impuzamugambi". The genocide took place in the context of the Rwandan Civil War, a conflict beginning in 1990 between the Hutu-led government and the Rwandan Patriotic Front (RPF). The latter was made up largely of Tutsi refugees whose families had fled to Uganda after the