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
Tutsi Since Burundi's independence, more extremist Tutsi came to power and oppressed the Hutus, especially those who were educated. Their actions led to the deaths of up to 200,000 Hutus. Overt discrimination from the colonial period was continued by different Rwandan and Burundian governments, including identity cards that distinguished Tutsi and Hutu. In 1993, Burundi's first democratically elected president, Melchior Ndadaye, a Hutu, was assassinated by Tutsi officers, as was the person entitled to succeed him under the constitution. This sparked a genocide in Burundi between Hutu political structures and the Tutsi military, in which "possibly as many as 25,000 Tutsi"