The Bantu speakers from Africa are often considered to be a culturally, linguistically, and genetically homogeneous group because of relatively recent rapid expansion, but at the same time, importance of interaction between the Bantu and non-Bantus in East Africa has been recognized (Cavalli-Sforza et al., 1994; Salas et al., 2002). In this article, Castrì et al. address the problem of the Bantu expansion based on their analyses of mtDNA variation among two Bantu populations, Hutu from East Africa and Shona from southeastern Africa, and their data suggests that East African Bantu populations are genetically different from Central African and southeastern African Bantu populations as a result of varying degree of interaction took place between the Bantu and non-Bantu populations.
Haplogroup frequencies of the Hutu and Shona are very different. Hutu have many East African haplogroups, while the Shona have haplogroups common in other Bantu populations. Hutu and Sukuma tend to be outliner on the plots created with correspondence analysis and multidimensional scaling analysis. On the other hand, Central African and southeastern African Bantu populations, including the Shona, form a mega cluster. Migration rates estimated using MIGRATE support these observation and migration rate between East African Bantu and non-Bantu East Africans was high.
Recently anthropologists are moving away from a simplistic view of Bantu expansion that dominated until 1990s. Anthropologists no longer believe that the Bantu speakers are culturally and genetically homogenous group. Castrì et al. follow this trend and argue that various processes (drift, gene flow among the Bantu-speaking populations, and gene flow between Bantu and non-Bantu populations) took place during and after the expansion. They did a great job evaluating the Bantu expansion and they recognized that there were interactions between the Bantu and non-Bantu populations in East Africa. However, their evaluation of Bantu expansion remained in general level and they did not go further to assess what kind of interactions took place between the Bantu and non-Bantu populations.
