Exploring the spread of Bantu speakers across Africa
About 6 000 to 4 000 years ago, there began what scientists consider the most dramatic demographic event in Late Holocene Africa. This event was the expansion of people speaking Bantu languages throughout Africa, and it drastically reshaped the continent’s linguistic, cultural and biological landscape. Today, roughly 350 million people across 9 million square kilometres in Africa speak at least one of more than 500 Bantu languages. But how, precisely, did this expansion happen? A new study supported by the AfricanNeo, BantuFirst, CODEV and cGEM projects has shed valuable light on the matter. To gain insight into the large-scale expansion, the researchers analysed a comprehensive data set of genomic data on 1 763 individuals in 14 African countries, including 117 populations not represented in previous genomic studies. They also generated genomic data for 12 ancient individuals from previously unsampled Late Iron Age sites of south-central and southern Africa.
Moving away from western Africa
The research shows that there was a large expansion of Bantu-speaking populations with ancestry from western Africa that spread through the Congo rainforest to eastern and southern Africa. As the distance from western Africa increased, the genetic diversity among these populations decreased. The study identifies modern-day Zambia and the Democratic Republic of Congo as possible crossroads of interaction between different expansion routes. What makes this expansion so special? Most recent human expansions involved migration through regions with similar climates. However, the Bantu-speaking people traversed regions with extremely diverse climates ranging from Cameroon’s highlands and central Africa’s rainforests to savannas and south-western Africa’s arid regions. “Our spatial modelling and interdisciplinary approaches support a serial founder migration model, emphasising the demographic significance of the expansion of these populations,” observes study co-lead author Dr Cesar Fortes-Lima of AfricanNeo and CODEV project coordinator Uppsala University, Sweden, in a press release posted on ‘idw – Informationsdienst Wissenschaft’). Serial founder effects occur when populations migrate over long distances. Rapid movements are followed by periods of settlement, with each subsequent migration resulting in a loss of genetic diversity. The study also shows that Bantu speakers received significant gene flow from local groups in the regions they expanded into in subequatorial Africa. “This highlights the complex genetic history of Bantu-speaking people, and this insight has been deepened by the incorporation of ancient DNA from human remains dating back to the Late Iron Age, spanning 97 to 688 years before the present,” states co-lead author Dr Concetta Burgarella, also from Uppsala University. Study senior author Prof. Carina Schlebusch remarks: “Our research also delves into the routes and timing of the expansion of Bantu-speaking populations, providing insights into their initial expansion routes, and investigates the potential for spread-over-spread events, complicating the tracing of their dispersion through language data alone.” The new findings obtained with support from AfricanNeo (The African Neolithic: A genetic perspective), BantuFirst (The First Bantu Speakers South of the Rainforest: A Cross-Disciplinary Approach to Human Migration, Language Spread, Climate Change and Early Farming in Late Holocene Central Africa), CODEV (Co-diversification and co-evolution of human populations and cereals in Africa), and cGEM (the Center for Genomics, Evolution and Medicine) could be a valuable resource for population geneticists, archaeologists, historical linguists, anthropologists and historians. It could also be useful for the medical sector studying human genetic variation and health in African populations. For more information, please see: AfricanNeo project website BantuFirst project website CODEV project cGEM project website
Keywords
AfricanNeo, BantuFirst, CODEV, cGEM, Africa, Bantu, population, expansion, genetic diversity
