The Bantu expansion is the name for a postulated millennia-long series of migrations of speakers of the original proto-Bantu language group. The primary evidence for this expansion has been linguistic, namely that the languages spoken in Sub-Equatorial Africa are remarkably similar to each other. Attempts to trace the exact route of the expansion, to correlate it with archaeological evidence and genetic evidence, have not been conclusive; thus many aspects of the expansion remain in doubt or are highly contested.
The linguistic core of the Bantu family of languages, a branch of the Niger–Congo language family, was located in the adjoining region of Cameroon and Nigeria. From this core, expansion began about 3,000 years ago, with one stream going into East Africa, and other streams going south along the African coast of Gabon, Democratic Republic of the Congo, and Angola, or inland along the many south to north flowing rivers of the Congo River system. The expansion eventually reached South Africa probably as early as AD 300.
Theories on expansion
Initially archaeologists believed that they could find archaeological similarities in the ancient cultures of the region that the Bantu-speakers were held to have traversed; while linguists, classifying the languages and creating a genealogical table of relationships believed they could reconstruct material culture elements. They believed that the expansion was caused by the development of agriculture, the making of ceramics, and the use of iron, which permitted new ecological zones to be exploited. In 1966 Roland Oliver published an article presenting these correlations as a reasonable hypothesis.
The hypothesized Bantu expansion pushed out or assimilated the hunter-forager proto-Khoisan, who formerly inhabited Southern Africa. In Eastern and Southern Africa, Bantu-speakers may have adopted livestock husbandry from other unrelated Cushitic- and Nilotic-speaking peoples they encountered. Herding practices reached the far south several centuries before Bantu-speaking migrants did. Archaeological, linguistic, genetic, and environmental evidence all support the conclusion that the Bantu expansion was a significant human migration.
The Niger–Congo family comprises a huge group of languages spread throughout Sub-Saharan Africa. The Benue–Congo branch includes the Bantu languages, which are found throughout Central, Southern, and Eastern Africa.
A characteristic feature of most Niger–Congo languages, including the Bantu languages, is their use of tone. They generally lack case inflection, but grammatical gender is characteristic, with some languages having two dozen genders (noun classes). The root of the verb tends to remain unchanged, with either particles or auxiliary verbs expressing tenses and moods. For example, in a number of languages the infinitival is the auxiliary designating the future.
It is thought that Central African Pygmies and Bantus branched out from a common ancestral population c. 70,000 years ago. Many Batwa groups speak Bantu languages; however, a considerable portion of their vocabulary is not Bantu in origin. Much of this vocabulary is botanical, deals with honey collecting, or is otherwise specialised for the forest and is shared between western Batwa groups. It has been proposed that this is the remnant of an independent western Batwa (Mbenga or "Baaka") language.
Parts of what now is present-day Kenya and Tanzania were also primarily inhabited by agropastoralist Afro-Asiatic speakers from the Horn of Africa followed by a later wave of Nilo-Saharan herders.
c. 1000 BC to c. AD 500 
It seems likely that the expansion of the Bantu-speaking people from their core region in West Africa began around 1000 BC. Although early models posited that the early speakers were both iron-using and agricultural, archaeology has shown that they did not use iron until as late as 400 BC, though they were agricultural. The western branch, not necessarily linguistically distinct, according to Christopher Ehret, followed the coast and the major rivers of the Congo system southward, reaching central Angola by around 500 BC.
It is clear that there were human populations in the region at the time of the expansion, and Pygmies are their purer descendants. However, mtDNA genetic research from Cabinda suggests that only haplogroups that originated in West Africa are found there today, and the distinctive L0 of the pre-Bantu population is missing, suggesting that there was a complete population replacement. In South Africa, however, a more complex intermixing could have taken place.
Further east, Bantu-speaking communities had reached the great Central African rainforest, and by 2500 years ago (500 BC) pioneering groups had emerged into the savannas to the south, in what are now the Democratic Republic of Congo, Angola, and Zambia.
Another stream of migration, moving east by 3,000 years ago (1000 BC), was creating a major new population center near the Great Lakes of East Africa, where a rich environment supported a dense population. Movements by small groups to the southeast from the Great Lakes region were more rapid, with initial settlements widely dispersed near the coast and near rivers, due to comparatively harsh farming conditions in areas further from water. Pioneering groups had reached modern KwaZulu-Natal in South Africa by AD 300 along the coast, and the modern Limpopo Province (formerly Northern Transvaal) by AD 500.
From the 1200s to 1600s
Between the 13th and 15th centuries, the relatively powerful Bantu-speaking states on a scale larger than local chiefdoms began to emerge, in the Great Lakes region, in the savanna south of the Central African rainforest, and on the Zambezi river where the Monomatapa kings built the famous Great Zimbabwe complex. Such processes of state-formation occurred with increasing frequency from the 16th century onward. They were probably due to denser population, which led to more specialised divisions of labour, including military power, while making outmigration more difficult. Other factors were increased trade among African communities and with European, and Arab traders on the coasts; technological developments in economic activity, and new techniques in the political-spiritual ritualisation of royalty as the source of national strength and health.
Rise of the Zulu Empire (18th–19th centuries)
By the time Great Zimbabwe had ceased being the capital of a large trading empire, speakers of Bantu languages were present throughout much of southern Africa. Two main groups developed, the Nguni (Xhosa, Zulu, Swazi), who occupied the eastern coastal plains, and the Sotho–Tswana who lived on the interior plateau.
In the late 18th and early 19th century, two major events occurred. The Trekboers were colonizing new areas of southern Africa, moving northeast from the Cape Colony, and they came into contact with the Xhosa, the Southern Nguni. At the same time major events were taking place further north in modern-day KwaZulu-Natal. At that time the area was populated by dozens of small clans, one of which was the Zulu, then a particularly small clan of no local distinction whatsoever. In 1816 Shaka acceded to the Zulu throne. Within a year he had conquered the neighboring clans, and had made the Zulu into the most important ally of the large Mtetwa clan, which was in competition with the Ndwandwe clan for domination of the northern part of modern day KwaZulu-Natal.
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