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
Hutu Power and declared that any Hutu who did business with a Tutsi was a traitor to the Hutu people. The Commandments declared that "The Hutu should stop having mercy on the Tutsi" and referred to the Tutsis as "common Tutsi enemy". The Rwandan kingdom was traditionally ruled by a Tutsi mwami, or king; Historical evidence suggests that Hutu and Twa were included in government, although the Twa significantly less so than Hutu, who were more numerous. The Tutsi/Hutu divide has been referred to as a caste system. A Hutu could gain Tutsi status through marriage or through success. Tutsis, being primarily