Origins of Hutu, Tutsi and Twa adults has a high capacity for lactose digestion, a surprisingly high number for an agrarian people, which Mamdani suggests may be the result of centuries of intermarriage with Tutsi. Bethwell Ogot in the 1988 UNESCO "General History" further notes that the number of pastoralists in Rwanda increased sharply around the fifteenth century. Although Luis et al. (2004) in a more general study on bi-allelic markers in many African countries found a statistically significant genetic difference between Tutsi and Hutu, the overall difference were not large. Modern-day genetic studies of the Y-chromosome generally indicate that the Tutsi, like the Hutu, are
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"