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 only one dominated by an opposition party. Opposing the genocide, Habyalimana was able to keep relative calm in the province, until he was deposed by the extremist Sylvain Ndikumana. Finding the population of Butare resistant to murdering their fellow citizens, the government flew in militia from Kigali by helicopter, and they readily killed the Tutsi. Most of the victims were killed in their own villages or in towns, often by their neighbors and fellow villagers. The militia typically murdered victims with machetes, although some army units used rifles. The Hutu gangs searched out victims hiding in churches and school buildings,