W. D. Hammond-Tooke’s scientific contributions

... If Huffman (2007) is correct, then the ancestors of modern Nguni and Sotho-Tswana peoples (who make up a large part of contemporary South Africa) settled in the region from East Africa in the early thirteenth century. The fact that some of the Nguni, especially the Ndwandwe, migrated back northward to colonise areas in Malawi and Tanzania (east Africa) in the nineteenth century (Omer-Cooper 1966;Collett 1987) highlights a remarkable population reflux. Kopytoff (1987) discusses internal African frontiers as zones of innovation and conservatism where different groups were on the move, settling, before expanding again to reconfigure boundaries. ...

Reference:

Colonialism from within versus colonialism from outside: the archaeology of nineteenth-century Nguni expansion and British colonialism in southwestern Zimbabwe