Knowing very little detail about the history of the former Portuguese East Africa, I hadn't heard about this before, a second relatively autonomous eighteenth century expansion of European settlement in Southern Africa away from the more rigidly controlled (by European colonial governments/companies) coasts. This seems to be analogous at first to Boers expanding inland from the Cape, but had a very different character than in the also largely autonomous Dutch agricultural settlement of the Cape Province:
Early in the seventeenth century, the Portuguese government began to acknowledge the rights acquired by these estate-holders[, private Portuguese individuals who acquired land title from the Mwene Mutapa]. After 1629, when the government obtained pseudo-legal sovereignty over the Mwene Mutapa's realm, it tried to regularize relations along lines that had initially been devised to promote settlement in Brazil....
These constraints were generally ignored. Some prazos [(estates)] grew in size until they covered a thousand square miles or more. Successive generations of prazeros married spouses who might be Africans, Indians, or members of other estate-owning families. By the nineteenth century, four or five family groups of mixed descent—we might almost call them clans—owned vast stretches of land on either side of the Zambezi River, from Chicoa to the Indian Ocean. These families wielded virtually unlimited power throughout the area. Neither the neighboring African rulers nor the Portuguese government were able to control them....
Indeed, historical studies by Allen F. Isaacman and M.D.D. Newitt have shown that the prazos became more like African chiefdoms as the years went by. The prazeros and their families continued to use Portuguese names and titles and to profess Christianity; but they were barely literate, they spoke local African languages more than Portuguese, they were polygynous, they believed in witchcraft, and they performed the functions of African chiefs, including in some cases the ritual functions. In this way the Portuguese elements were gradually assimilated into the local African culture.
Curtin, et al. African History: From Earliest Times to Independence. Harlow: Longman, 1995.
Just as in the Americas, attributing the differences between activities by different colonial powers (and their settlers) to European cultural factors like Catholicism, Protestantism, Germanic, or Mediterranean culture is naive and rings of both Eurocentrism and the even narrower species of such found among, surprise, northern Europeans with that insidious ideology of separatism called, among other things, apartheid. The Cape Province and the Zambezi Valley were very different places: the first relatively sparsely settled by isolated pastoral and hunting peoples, the other one of the main sources of gold for the rich Indian Ocean trade routes – among the artifacts at the ruins of Great Zimbabwe, even after Rhodesians melted most of the valuables down were pottery from Iran and China.
In the same way, Spanish centers in the Americas were only so large and successful because they built on the structure of indigenous empires, and, as with any relationship where cultural exchange is both possible and advantageous, whether European, colonial, and recorded or ancient, pre-colonial, and not recorded (such as the first Bantu settlement of the Zambezi over two millennia ago), it tends to occur. It is often very unequal, particularly when migrants are economically powerful men, but it occurs, and the endurance of the power structures, myths, and legends of these men is the source of many of our illusions about identity and history—whether of Aryan North India, the extinction of the Celtic English, Han Chinese homogeneity. or "racially" pure Afrikaners or white Southerners in the U.S. Not everything is an illusion: languages are replaced and made extinct, people are enslaved and killed (the prazeros on the Zambezi themselves were good at this), and certain material cultures replace others, but something almost always endures. When nothing else does, it's ancestry. History has proven over and over than perception of ancestry turns into the reality of identity, so getting it right is very important.
What the Cape Province and British-settled North America really seem to have in common is not so much Germanic myth inspired apartheid, as much as dominant elements in those societies have tried, but the political and ideological institution of the same pushing off those people who do mix (and/or acknowledge) mixing into a legally separate caste identity: in South Africa, Coloureds, who are mixed Dutch, Khoikhoi, Malagasy, and Indonesian (the latter two groups slaves brought in from the Indian Ocean basin), and in the United States, the mixed, yet black, results of the one-drop rule. Yet... people passed into socioeconomically dominant groups whenever they could, with the result that there are many Southerners who are part African and many Afrikaners who are part Malagasy and Khoi.
Previous explanations of the difference between, say, the United States and Mexico, have tended to focus on the supposed higher Spanish Catholic tolerance for mixing resulting in a mixed population, and the lower English Protestant tolerance resulting in a non-mixed population. i would prefer to say that the difference is rather the acknowledgement of mixing, and thus the society allowing it to continue to take place multigenerationally rather than for people to be pushed off into one group or another and thus gradually become phenotypically less alike.
This distinction is extremely important. It acknowledges that people really do tend to be recently mixed in all descents from seventeenth century settler societies, as autosomal DNA tests are beginning to show. This is relevant not just to populations who have long-term ancestry in settler societies founded in post-Columbian colonial efforts. Even if your parents migrated from Ethiopia to Canada thirty years ago (or, of course, never left Ethiopia at all); these are just among the best documented and socially relevant in today's global identity structures.
If the difference is ideology formed in the past, it can be nullified in ideology formed about the past. Genealogy, traditional combined with genetic, has an important role to play here, as our results and those of our cousins begin to show the reality of a world in which ancestry is never location-bound for far in the past.