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
Rape during the Rwandan genocide to be an act of genocidal rape. The mass rapes were carried out by the Interahamwe militia and members of the Hutu civilian population, both male and females, the Rwandan military, and the Rwandan Presidential Guard. The sexual violence was directed at the national and local levels by political and military leaders in the furtherance of their goal, the destruction of the Tutsi ethnic group. There was extensive use of propaganda through both print and radio to incite violence against women, with both mediums being used to portray Tutsi women as untrustworthy, and as acting against the Hutu majority. The