Origins of Hutu, Tutsi and Twa on economic criteria. Formal and discrete social divisions were consequently imposed upon ambiguous biological distinctions. To some extent, the permeability of these categories in the intervening decades helped to reify the biological distinctions, generating a taller elite and a shorter underclass, but with little relation to the gene pools that had existed a few centuries ago. The social categories are thus real, but there is little if any detectable genetic differentiation between Hutu and Tutsi. Tishkoff et al. (2009) found their mixed Hutu and Tutsi samples from Rwanda to be predominately of Bantu origin, with minor gene flow from Afro-Asiatic
History of Rwanda dominated by the majority Hutu under President Grégoire Kayibanda. Unsettled ethnic and political tensions were worsened when Juvénal Habyarimana, who was also Hutu, seized power in 1973. In 1990, the Rwandan Patriotic Front (RPF), a rebel group composed of 10,000 Tutsi refugees from previous decades of unrest, invaded the country, starting the Rwandan Civil War. The war ground on, worsening ethnic tensions, as the Hutu feared losing their gains. The assassination of Habyarimana was the catalyst for the eruption of the 1994 genocide, in which hundreds of thousands of Tutsis and some moderate Hutus were killed. The Tutsi RPF conquered