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 own, but by this stage the Hutu had full backing from the Belgian administration who wanted to overturn the Tutsi domination. In early 1960, the Belgians replaced most Tutsi chiefs with Hutu and organised mid-year commune elections which returned an overwhelming Hutu majority. The king was deposed, a Hutu dominated republic created, and the country became independent in 1962. As the revolution progressed, Tutsi began leaving the country to escape the Hutu purges, settling in the four neighbouring countries: Burundi, Uganda, Tanzania and Zaire. These exiles, unlike the Banyarwanda who migrated during the pre-colonial and colonial era, were regarded as