Bantu expansion shows that habitat alters the route and pace of human dispersals

Abstract

Unlike most other biological species, humans can use cultural innovations to occupy a range of environments, raising the intriguing question of whether human migrations move relatively independently of habitat or show preferences for familiar ones. The Bantu expansion that swept out of West Central Africa beginning ∼5,000 y ago is one of the most influential cultural events of its kind, eventually spreading over a vast geographical area a new way of life in which farming played an increasingly important role. We use a new dated phylogeny of ∼400 Bantu languages to show that migrating Bantu-speaking populations did not expand from their ancestral homeland in a "random walk" but, rather, followed emerging savannah corridors, with rainforest habitats repeatedly imposing temporal barriers to movement. When populations did move from savannah into rainforest, rates of migration were slowed, delaying the occupation of the rainforest by on average 300 y, compared with similar migratory movements exclusively within savannah or within rainforest by established rainforest populations. Despite unmatched abilities to produce innovations culturally, unfamiliar habitats significantly alter the route and pace of human dispersals.human dispersal | phylogeography | phylogenetics | languages | Bantu

The deep human prehistory of global tropical forests and its relevance for modern conservation

“…In Amazonia, the adoption of Mesoamerican maize (Zea mays) dates back to at least 6,000 BP 70 and the plant was an important part of regional diets by the late Holocene 71 . In Africa, Bantu agriculturalists farming pearl millet and cattle appear to have expanded into the tropical rainforests of western and central Africa, c. 2.5 ka, when their extent was greatly contracted 24 . This expansion is suggested to have resulted in severe erosion and forest fragmentation in eastern and central Africa 72 .…”

“…22 ). This view was further promoted by archaeologists, who, for example, saw tropical forests as barriers to the expansion of Late Pleistocene Homo sapiens foragers 23 , and also deemed them incapable of supporting agricultural populations 24 . This bias has been exacerbated by the generally-poor preservation of organic archaeological remains in tropical forest environments (e.g.…”

Bantu Lexical Reconstruction

“…Bantu classification research is today almost entirely driven by phylogenetic methods (cf. Currie et al 2013;de Schryver et al 2015;Grollemund et al 2015, to cite only some of the most recent studies). A better integration of classical reconstruction and classification research-to start with at the level of major Bantu subgroups-would allow for alternative approaches and to test the genealogical validity of phylogenetic subgroups obtained through quantitative studies mainly based on basic vocabulary.…”

Prehistoric Bantu-Khoisan language contact

“…It is commonly assumed that this immense spread was accomplished by the gradual dispersal of expanding sedentary communities from the Grassfields region of Cameroon, starting 5,000 years ago and reaching southern Africa some 3,000 years later (Vansina, 1995: 189;Phillipson, 2005: 245ff. ; Blench, 2006: 126;Bostoen, 2007;Grollemund et al, 2015). In contrast to the Bantu languages, which are all closely related, the Khoisan languages of southern Africa belong to three separate language families, the genealogical relationship of which has yet to be demonstrated (Güldemann, 2014).…”