Hutu Rwanda, this led to the "Social revolution" and Hutu violence against Tutsis. Tens of thousands of Tutsis were killed and many others fled to neighboring countries, such as Burundi, Uganda and expanding the Banyamulenge Tutsi ethnic group in the South Kivu region of the Belgian Congo. Later, exiled Tutsis from Burundi invaded Rwanda, prompting Rwanda to close its border with Burundi. In Burundi, a campaign of genocide was conducted against Hutu population in 1972, and an estimated 100,000 Hutus died. In 1993, Burundi's first democratically elected president, Melchior Ndadaye, who was Hutu, was believed to be assassinated by Tutsi officers,
Origins of Hutu, Tutsi and Twa largely of Bantu extraction (60% E1b1a, 20% B, 4% E3). Paternal genetic influences associated with the Horn of Africa and North Africa are few (under 3% E1b1b), and are ascribed to much earlier inhabitants who were assimilated. However, the Tutsi have considerably more haplogroup B paternal lineages (14.9% B) than do the Hutu (4.3% B). Trombetta et al. (2015) found 22.2% of E1b1b in a small sample of Tutsis from Burundi, but no bearers of the haplogroup among the local Hutu and Twa populations. The subclade was of the M293 variety, which suggests that the ancestors of Tutsis in this