Hutu 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 communities (17.7% Afro-Asiatic genes found in the mixed Hutu/Tutsi population). Hutus speak Rwanda-Rundi as their native tongue, which is a member of the Bantu subgroup of the Niger–Congo language
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;