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
Rwanda Nziza under the presidencies of Gregoire Kayibanda and Juvénal Habyarimana, were marked by continued cycles of violence, culminating in the 1990s with the launch of the Rwandan Civil War by exiled Tutsi led by Paul Kagame, the assassination of President Habyarimana, and the 1994 Rwandan Genocide, in which between 500,000 and 1,000,000 Tutsi and politically moderate Hutu were killed by Hutu extremists, on the orders of the interim government, in the space of just 100 days. The genocide was ended when Kagame's rebel army took control of the country in July 1994. A period of reconciliation began, as a unity government