Significance: Humans are uniquely capable of using cultural innovations to occupy a range of environments, raising the intriguing question of whether historical human migrations have followed familiar habitats or moved relatively independently of them. Beginning ∼5,000 y ago, savannah-dwelling populations of Bantu-speaking peoples swept out of West Central Africa, eventually occupying a vast geographical area. We show that this expansion avoided unfamiliar rainforest habitats by following savannah corridors that emerged from the Congo rainforest, probably from climate change. When Bantu speakers did move into the rainforest, migration rates were delayed by on average 300 y compared with similar movements on the savannah. Despite unmatched abilities to produce innovations culturally, unfamiliar habitats significantly alter the route and pace of human dispersals.

This article reviews evidence from biogeography, palynology, geology, historical linguistics, and archaeology and presents a new synthesis of the paleoclimatic context in which the early Bantu expansion took place. Paleoenvironmental data indicate that a climate crisis affected the Central African forest block during the Holocene, first on its periphery around 4000 BP and later at its core around 2500 BP.We argue here that both phases had an impact on the Bantu expansion but in different ways. The climate-induced extension of savannas in the Sanaga-Mbam confluence area around 4000–3500 BP facilitated the settlement of early Bantu-speech communities in the region of Yaoundé but did not lead to a large-scale geographic expansion of Bantu-speaking village communities in Central Africa. An extensive and rapid expansion of Bantu speech communities, along with the dispersal of cereal cultivation and metallurgy, occurred only when the core of the Central African forest block was affected around 2500 BP. We claim that the Sangha River interval in particular constituted an important corridor of Bantu expansion. With this interdisciplinary review, we substantially deepen and revise earlier hypotheses linking the Bantu expansion with climate-induced forest openings around 3000 BP

Popular belief has it that the Bantu Expansion was a farming/language dispersal. However, there is neither conclusive archaeological nor linguistic evidence to substantiate this hypothesis, especially not for the initial spread in West-Central Africa. In this chapter we consider lexical reconstructions for both domesticated and wild plants in Proto-West-Coastal Bantu associated with the first Bantu speech communities south of the rainforest about 2500 years ago. The possibility to reconstruct terms for five different crops, i.e. pearl millet ( Pennisetum glaucum ), okra ( Hibiscus/Abelmoschus esculentus ), cowpea ( Vigna unguiculata ), Bambara groundnut ( Vigna subterranea ) and plantain ( Musa spp .), indicates that by that time Bantu speakers did know how to cultivate plants. At the same time, they still strongly depended on the plant resources that could be collected in their natural environment, as is evidenced by a preliminary assessment of reconstructible names for wild plants. Agriculture in Central Africa was indeed “a slow revolution”, as the late Jan Vansina once proposed, and certainly not the principal motor behind the early Bantu Expansion.

The expansion of Bantu languages represents one of the most momentous events in the history of Africa. While it is well accepted that Bantu languages spread from their homeland (Cameroon/Nigeria) approximately 5000 years ago (ya), there is no consensus about the timing and geographical routes underlying this expansion. Two main models of Bantu expansion have been suggested: The ‘early-split’ model claims that the most recent ancestor of Eastern languages expanded north of the rainforest towards the Great Lakes region approximately 4000 ya, while the ‘late-split’ model proposes that Eastern languages diversified from Western languages south of the rainforest approximately 2000 ya. Furthermore, it is unclear whether the language dispersal was coupled with the movement of people, raising the question of language shift versus demic diffusion. We use a novel approach taking into account both the spatial and temporal predictions of the two models and formally test these predictions with linguistic and genetic data. Our results show evidence for a demic diffusion in the genetic data, which is confirmed by the correlations between genetic and linguistic distances. While there is little support for the early-split model, the late-split model shows a relatively good fit to the data. Our analyses demonstrate that subsequent contact among languages/populations strongly affected the signal of the initial migration via isolation by distance.

Chapter 6 is about common Bantu word formation strategies. Bantu languages are rich in morphology, equally so when it comes to derivation. This chapter surveys the major derivational processes, such as verb-to-verb derivation, verb-to-noun derivation, noun-to-noun derivation and noun-to-verb derivation, as well as different other ways of forming words, such as the clitising of pre- and post-stem elements, compounding and reduplication.