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
Tutsi after mid-1600. Beginning in about 1880, Roman Catholic missionaries arrived in the Great Lakes region. Later, when German forces occupied the area during World War I, the conflict and efforts for Catholic conversion became more pronounced. As the Tutsi resisted conversion, missionaries found success only among the Hutu. In an effort to reward conversion, the colonial government confiscated traditionally Tutsi land and reassigned it to Hutu tribes. In Burundi, meanwhile, Tutsi domination was even more entrenched. A ruling faction, the Ganwa, soon emerged from amongst the Tutsi and assumed effective control of the country's administration. The area was ruled as