Origins of Hutu, Tutsi and Twa of neighboring people, it was almost non-existent among Rwandan Tutsi. Presence of the sickle cell trait is evidence of survival in the presence of malaria over many centuries, suggesting differing origins. Regional studies of the ability to digest lactose are also supportive. The ability to digest lactose among adults is widespread only among desert-dwelling nomadic groups that have depended upon milk for millennia. Three quarters of the adult Tutsi of Rwanda and Burundi have a high ability to digest lactose, while only 5% of the adults of the neighboring Shi people of eastern Congo can. Among Hutu, one in three
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