Genetics and Advanced article Article Contents Demographic History of • Introduction • The Migration of Bantu-speaking Peoples out the Bantu of West Africa • Migratory Routes Jorge Rocha, CIBIO/InBIO and Department of Biology, Faculty of Sciences, Univer- • Admixture with Other Populations sity of Porto, Porto, Portugal Online posting date: 15th November 2016 Anne-Maria Fehn, Department of Linguistic and Cultural Evolution, Max-Planck Institute for the Science of Human History, Jena, Germany and CIBIO/InBIO, University of Porto, Porto, Portugal Peoples speaking languages of the Bantu fam- of these languages suggests that their present distribution must ily are widespread in sub-Saharan Africa, from be the result of a relatively recent, rapid spread, which came the equatorial rainforest to the Cape of Good to be known as the Bantu expansion. However, there are many Hope. Their present-day distribution is the result aspects of the history of Bantu languages and Bantu-speaking of a remarkable expansion, which started about populations that remain to be clarified and are the object of 4000–5000 years ago in the borderland between intense multidisciplinary research, involving contributions from Cameroon and Nigeria. The genetic distances linguistics, ethnography, archaeology and genetics. Until recently, most studies on the genetics of Bantu-speaking among Bantu-speaking populations are signifi- peoples were based on the study of mitochondrial deoxyribonu- cantly lower than those between the Bantu and cleic acid (mtDNA) and the nonrecombining region of the Y chro- other ethnolinguistic groups from Africa, suggest- mosome (NRY). As both mtDNA and NRY lack recombination, ing an actual movement of people, rather than it is relatively easy to infer their phylogenies by reconstructing cultural diffusion. However, this genetic homo- the order in which mutations accumulate in different lineages. geneity places a challenge to the reconstruction See also: Mitochondrial Genome: Evolution; Y Chromosome; of their actual routes of dispersal, with existing Chromosome Y; Mitochondrial DNA Polymorphisms.The hypotheses being mainly based on data from lin- analysis of the geographic distribution of phylogenetically related guistics and archaeology. While the indigenous mtDNA and NRY lineages, known as phylogeography, has pro- populations they encountered did not provide vided valuable insights into the genetic relationships between dif- a major contribution to the Bantu gene pool at ferent Bantu-speaking peoples and between Bantu and non-Bantu large, admixture studies reveal different patterns populations (Pereira et al., 2001; Salas et al., 2002; Berniell-Lee of social interaction, which range from Bantu et al., 2009; de Filippo et al., 2011). See also: Phylogeography; dominance in the rainforest to a more levelled Genetic Diversity in Africa. Moreover, owing to their uni- exchange in southern Africa. parental patterns of inheritance, mtDNA and NRY have been used to explore female and male-specific aspects of Bantu genetic vari- ation. However, these markers represent only a very small fraction of the entire genome and can only offer limited information about Introduction the history of populations. Recent progresses in DNA sequencing and single-nucleotide The Bantu family, whose name derives from the shared root polymorphism (SNP) array technologies have made it possible *-ntu ‘person’, is a group of approximately 500 closely related to generate genome-wide data based on thousands of autosomal languages that belong to a recently differentiated subbranch of the genetic polymorphisms. See also: Single Nucleotide Polymor- Niger–Congo phylum of African languages (Figure 1). Presently, phism (SNP); Single Nucleotide Polymorphisms (SNPs): the Bantu languages are spoken by about 250 million people Identification and Scoring; HapMap Project; Whole Genome across a large geographical area in sub-Saharan Africa (Figure 1). Resequencing and 1000 Genomes Project; High-Throughput The wide distribution and low degree of internal differentiation Single Nucleotide Polymorphisms Genotyping Technologies; eLS subject area: Evolution & Diversity of Life Next Generation Sequencing Technologies and Their Appli- cations. The use of these genetic datasets composed of multiple, How to cite: independently evolving genetic systems in combination with Rocha, Jorge and Fehn, Anne-Maria (November 2016) Genetics and Demographic History of the Bantu. In: eLS. John Wiley & new analytical tools created a unique opportunity to address Sons, Ltd: Chichester. outstanding questions of population history with an unprece- DOI: 10.1002/9780470015902.a0022892 dented resolution (Pugach and Stoneking, 2015). See also: eLS © 2016, John Wiley & Sons, Ltd. www.els.net 1 Genetics and Demographic History of the Bantu Figure 1 Distribution of non-Bantu Niger–Congo (yellow), West Bantu (Orange) and East Bantu (red) languages. Language groups were assigned according to the affiliation of the most widely distributed languages in the respective countries. The star indicates the approximate origin of the Bantu expansion. Reconstructing Human History Using Autosomal, Y-Chro- due to the recent diversification of all Bantu languages from a mosomal and Mitochondrial Markers; Human Relationships common ancestor. The borderland between south-eastern Nige- Inferred from Genetic Variation ria and western Cameroon was suggested by Greenberg (1972)to Although the sampling coverage and marker density in Bantu be the original location of the ancestral Bantu language and this genetic studies is still far from being fully satisfactory, there idea is now widely accepted. The reasoning behind this assump- are many important aspects of the demographic history of tion is that it is there that Bantu languages are more diverse and Bantu-speaking peoples that have been uncovered with the meet with their closest relatives of the Niger–Congo family – the available mtDNA, NRY and autosomal genome-wide data. In so-called Bantoid or Wide Bantu languages (Figure 1). However, this article, we present a brief outline of the current state of the the linguistic data alone does not tell us whether the spread of research on the genetics of Bantu peoples by highlighting these Bantu languages and culture actually involved a movement of contributions and relating them with the insights provided by people or whether it is merely the result of cultural diffusion. See other disciplines. also: Human Genetics and Languages. Yet, these two alterna- tives imply very different predictions about the genetic composi- tion of Bantu-speaking populations from different parts of Africa. The Migration of Bantu-speaking If the spread of Bantu languages was driven only by cul- Peoples out of West Africa tural diffusion and language shift, the different Bantu-speaking populations would not share a distinctive genetic composition The most obvious evidence for the spread of Bantu languages and Bantu groups would not be expected to be more simi- is, of course, provided by linguistics. Early travellers already lar to each other than to their non-Bantu closest neighbours. noticed that many of the languages spoken in sub-Saharan Africa These expectations are clearly not met by the available genetic are similar to each other. Today, we know that this similarity is data. For example, Tishkoff et al. (2009), using a set of 1300 2 eLS © 2016, John Wiley & Sons, Ltd. www.els.net Genetics and Demographic History of the Bantu 0.02–0.05 0.05–0.15 0.15–0.25 0.25–0.35 0.35–0.45 0.45–0.55 0.55–0.65 0.65–0.75 0.75–0.84 Figure 2 Geographical distribution of the genetic component associated with Niger–Congo-speaking groups. The darker the tone is, the higher is the frequency of the genetic component (see scale). Lighter coloured regions include a comparatively high number of non-Niger–Congo-speaking populations. The map was drawn using data from Tishkoff et al. (2009). autosomal polymorphisms, showed that most Bantu and other E1b1a (Underhill et al., 2001;Rosaet al., 2007; Berniell-Lee Niger–Congo-speaking populations from widely separated geo- et al., 2009; de Filippo et al., 2011). The most frequent mater- graphical areas do share a genetic component that clearly sets nal lineages found in Bantu populations belong to a more diverse them apart from African populations that speak other languages set of haplogroups (mainly L0a, L1c, L2a, L3b and L3e) than (Figure 2). Conversely, Bantu-speaking groups that do not share observed for the NRY. However, these populations are also this genetic component are exceptional. The most prominent case closely related on the basis of their mtDNA sequences and trace is represented by the genetically and culturally distinct Pygmy the bulk of their maternal heritage to western Central Africa hunter-gatherers from the western Congo Basin, who speak Bantu (Salas et al., 2002; Beleza et al., 2005; Coelho et al., 2009). languages probably due to language shift (Bahuchet, 2012). How- The congruence between the genetic patterns observed with ever, these populations are geographically close to and geneti- different types of markers has been further confirmed by de Fil- cally admixed with non-Pygmy Bantu-speaking peoples, indicat- ippo et al. (2012), who found that the genetic distances among ing that language shift was promoted by the actual migration of Bantu-speaking populations based on mtDNA, NRY and autoso- these peoples into Pygmy territories (see below). mal data were all significantly lower than those between the Bantu The genetic unity