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
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"