Peopling history of Africa A multidisciplinary perspective

Recent paleoanthropological studies have explored increasingly past population diversity in an ecomorphological perspective. Biomechanical analyses have shown that measurements of both quantity and distribution of diaphyseal cortical bone reflects the pattern of usual loads. Consequently, long bone robusticity reflect degrees of physical activity and therefore mobility patterns that vary spatio-temporally. The aim of the present project is to explore long bone robusticity in Central African prehistoric populations, a key region to understand population diversity and history in sub-Saharan Africa. Population samples were selected, in order to assess variation in relation to different economical strategies (hunter-gathers vs agriculturists) as well as different chronological periods (Late Stone Age vs Iron Age). A total number of 40 individuals were analysed from the following groups: Pygmies (Democratic Republic of Congo; 19th – 20th c AD), Upemba Valley, (DRC; 11th-15th c AD), Shum Laka (Cameroon; 4500-1500 BC) and Ishango (DRC; Late Pleistocene to early Holocene). All the bones of both upper and lower limbs were CT-scanned at Erasme Hospital (Université Libre de Bruxelles) in order to analyse their cross-sectional geometry. After determining maximum length of each bone, cross sections at standardized location (20 %, 35%, 50%, 65% and 80%) were analyzed with NIH ImageJ and the BoneJ pluging. The following variables were recorded: cortical area (CSA), total area (TA), second moments of area (Imin, I max) and the polar moment of area (J). Preliminary results showed that, after size correction, the variable J (Imin+Imax= J) appear to show statistically significant differences between both, the upper and lower limbs, and the hunter-gatherers and farmers.

The time transects of African genetic history are challenging to reconstruct for the wide extent of population differentiation, migration and contact. Ancient DNA provides a direct window into the past, but up to now only a few studies were able to successfully recover DNA from ancient African remains, due to the continent environmental features affecting preservation. As an alternative resource to look at ancient African genetic variation, we analyzed archaeological remains of African origin outside of the continent, from the earliest colonial time. Here we report an archaeogenetic study of three enslaved Africans from Mexico City buried at the San José de los Naturales Royal Hospital (Hospital Real de San José de los Naturales). We analyzed ancient human genomes, including uniparental markers, together with strontium isotopes, δ13C and δ15N measurements of dentine, and considered ethnohistorical information to reconstruct their origin. Our results support that the three individuals were probably among the first enslaved Africans to reach the central plateau of New Spain in the 16thcentury. Their individual biological affinity estimated from the macromorphoscopic characteristics, uniparental markers, HLA haplotypes and admixture estimates point to a common West African origin, compatible with populations from the Atlantic-Congo language family, but their genetic profiles are quite diverse. We suggest that slave migrants from West Africa four centuries ago were harboring a very diverse genetic makeup, including profiles that are found today surprisingly in eastern and southern Africa.

Southern African indigenous groups, traditionally hunter-gatherers (San) and herders (Khoekhoe), have a long history in southern Africa. Their ancestors were largely isolated up until ~2,000 years ago before the arrival of pastoralists and farmers in the southern African region. Assessing relationships among regional Khoe-San groups have been challenging due to admixture with immigrant populations that obscured the past population affinities and gene-flow among these autochthonous communities. We re-evaluate a combined genome-wide dataset of previously published southern Africa Khoe-San populations in conjunction with novel data from Khoe-San individuals collected in Xade (Central Kalahari Game Reserve, Botswana) prior to their resettlement outside the reserve. After excluding regions in the genome that trace their ancestry to recent migrant groups, the genetic diversity of 20 Khoe-San groups fitted an isolation-by-distance model. Even though isolation-by-distance explained most genetic affinities between the different autochthonous groups, additional signals of contact and admixture between Khoe-San groups could be detected. For instance, we found stronger genetic affinities, than what would be explained by isolation-by-distance gene flow, between the two geographically separated Khoe-San groups, who speak branches of the Kx’a-language family (ǂHoan and Ju). We also scanned the genome-wide data for signals of adaptive gene flow from farmers/herders into Khoe-San groups and identified a number of genomic regions potentially introduced by the arrival of the new groups. This study provides a comprehensive picture of affinities among Khoe-San groups, prior to the arrival of recent migrants, and found that these affinities are primarily determined by the geographic landscape.

We present findings from ongoing cross-disciplinary research to attest the accuracy of statement, “Historically, the first Dogon settlement of the [Bandiagara] Cliff zone can be placed within a range of two centuries, between 1230 and 1430 AD” (Mayor et al., 2005, 31). That is, while studies prior to those of Mayor et al. depicted Dogon people migrating as a unit, settling near Bandiagara around 500 years ago, and then spreading out along the cliffs to where they are today, our linguistic comparisons demonstrate a split-off between the Dogon languages spoken among the Ibi and Sangha villages for which the 500 year date has been associated and the other estimated 20 Dogon languages, with further divisions incrementally increasing until the projected 1500 year mark. Further, by using the date estimated by Mayor et al. (2014) of 4000 years of continual inhabitation of the Bandiagara Escarpment as a point of departure, and a constant mutation rate for language change, we expand upon previous work by Moran and Prokić (2013) and Prokhorov et al. (2012), to propose that a new division along north-south lines may be more genetically and geographically intuitive in terms of a historical expansion from different locations than their east-west delineation. Our quantitative studies are based on state-of-the-art methods for automatic word comparison across the Dogon languages (List et al. 2017b), and our phylogenetic analysis uses archaeological and climatic priors for the Dogon settlement provided by Mayor et al., enabling us to view a time-depth for the Dogon-speaking populations.

For a long time, it has been argued that current African population diversity is a product of people’s migration and interactions over time and space. Various events in the continent have been recorded, especially as they relate to the Iron Age Bantu migrations. This paper presents the archaeological evidence of people’s migrations and interactions in southern Tanzania from the early Iron Age to the 19th century. The data was collected in 2014 at Ruvuma region (about 1054 kilometers) from the Swahili coast. The study aimed at exploring the coast-interior interactions which could have existed over time and space (if any). By employing the archaeological survey and excavation, this study revealed archaeological evidence in terms of pottery, beads, metal and cultural flora. The broader intra and interregional comparison of those evidence indicated that, the local pottery (early and later Iron Age) bares affinities with other pottery reported along the Swahili coast and other interior parts of the region including the neighbouring countries of Zambia and Malawi. Other evidence, particularly imported pottery, beads, coin and glass, is dated between 17th-19th centuries. This imported evidence could have been brought in interior southern Tanzania as a result of 19th century caravan trade. Having drawn examples from southern Tanzania, it is likely to say the current population variability in Africa is a continuous process which has been influenced both internally and externally. Example of such influences could be events such as migrations (Bantu, Ngoni), conflicts and wars, as well as intra-inter trade and exchange.

The archaeological signature of the expanding villages through Central Africa before 1500 BP has been vastly improved by research carried out since 2005. Mostly relying on Master and Doctoral theses, the data has been often left unpublished. Other results have been obtained by way of preventive or rescue archaeology contracts, and a few via research programs excavating new and very interesting information from Angola, Cameroon, the Democratic Republic of Congo, Equatorial Guinea, and Gabon. Using the same protocol, published work has been reevaluated to further a previous synthesis permitting now a more detailed picture of the first villages expansions. Though good paleo-economy information is still lacking due to a dearth in specific techniques to recover macro plant remains during archaeological fieldwork, important associated data has been forthcoming from recent paleo-environmental and genetic studies which will be briefly summarized. The first results of the BantuFirst research project presented at this meeting by K. Bostoen is part of this new and needed approach. Today, the overall picture is one of a small number of villages settling in southern Cameroon and on the Gabonese coast before 2,600 BP, probably around and before 3000 BP, still using stone tools, with pioneer small scale settlements at the latest around 2,500-2,400 BP on the coast of the Republic of Congo, in the Kongo Central and Equateur provinces of the Democratic Republic of Congo. The associated pottery is evidence to a lack of close connection between these early migrants, though some overall relationships can be identified. Later, roughly around 2200-2000 BP, other distinct Groups, practicing iron working, settle in central and western Gabon, on the Republic of Congo coast, in the Kongo Central province of the DRC and north-western Angola, while in Katanga province of the DRC, the south-eastern part of Central Africa, Early Iron Age communities only settle there around 1,400 BP. To sum up, we find a quite complex pattern of settlement and evidence of several archaeological transitions best explained as waves of migrating peoples associated to specific cultural material and economic strategies. Where possible, contacts and patterns of exchanges between hunter-collectors and villagers will be discussed.