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
Burundi some Hutu felt this was unjust and ethnic tensions were further increased. In October 1965, an attempted coup d'état led by the Hutu-dominated police was carried out but failed. The Tutsi dominated army, then led by Tutsi officer Captain Michel Micombero purged Hutu from their ranks and carried out reprisal attacks which ultimately claimed the lives of up to 5,000 people in a precursor to the 1972 Burundian Genocide. King Mwambutsa, who had fled the country during the October coup of 1965, was deposed by a coup in July 1966 and his teenage son, Prince Ntare V, claimed the throne.