Tutsi rule. The Tutsi aristocracy or elite was distinguished from Tutsi commoners, and wealthy Hutu were often indistinguishable from upper-class Tutsi. When the Belgian colonists conducted censuses, they wanted to identify the people throughout Rwanda-Burundi according to a simple classification scheme. They defined "Tutsi" as anyone owning more than ten cows (a sign of wealth) or with the physical feature of a longer nose, or longer neck, commonly associated with the Tutsi. The Belgians believed that some Tutsis had facial characteristics that were generally atypical of other Bantus. They sought to explain these purported divergent physical traits by postulating admixture with
Hutu of Rwandan national unity, but has been criticized as an attempt at historical revisionism. Still others suggest that the two groups are related but not identical, and that differences between them were exacerbated by Europeans, or by a gradual, natural split, as those who owned cattle became known as Tutsi and those who did not became Hutu. Mahmood Mamdani states that the Belgian colonial power designated people as Tutsi or Hutu on the basis of cattle ownership, physical measurements and church records. There is an ongoing debate as to whether the Hutu and Tutsi are really separate groups or not;