Subsistence strategy was the main factor driving population differentiation in the bidirectional corridor of the African Sahel

• Published in: American journal of physical anthropology Vol. 171; no. 3; pp. 496 - 508
• Main Authors: Nováčková, Jana, Čížková, Martina, Mokhtar, Mohammed G., Duda, Pavel, Stenzl, Vlastimil, Tříska, Petr, Hofmanová, Zuzana, Černý, Viktor
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01-03-2020; Wiley Subscription Services, Inc
• Subjects: African Sahel; Archaeological evidence; Baggarization; Bidirectionality; Chromosomes; Deoxyribonucleic acid; Differentiation; DNA; Farmers; Farming; Genetic structure; Geography; Haplotypes; Linguistics; Mitochondrial DNA; mtDNA; Nomads; Pastoralism; Population; Population differentiation; Population structure; Sedentary; Sequences; subsistence; Y chromosome; African Sahel; Baggarization; mtDNA; subsistence; Y chromosome
• ISSN: 0002-9483; 1096-8644; 2692-7691
• DOI: 10.1002/ajpa.24001

Objectives
The Sahel belt is occupied by populations who use two types of subsistence strategy, nomadic pastoralism and sedentary farming, and who belong to three linguistic families, Niger‐Congo, Nilo‐Saharan, and Afro‐Asiatic. Little is known, however, about the origins of these two populations and their mutual genetic relationships.
Materials and Methods
We have built a large dataset of mitochondrial DNA sequences and Y chromosomal STR haplotypes of pastoralists and farmers belonging to all three linguistic phyla in the western, central, and eastern parts of the Sahel. We calculated pairwise genetic, geographic, and linguistic distances between populations and analyzed the effects of geography, language, and subsistence on population genetic structure.
Results
We found that subsistence mode significantly contributed to the generally low population structure in the Sahel and that language affiliation plays a more important role for pastoralists than for farmers. We also demonstrated that geographic isolation significantly influenced the population structure of sedentary farmers but not of nomadic pastoralists. Finally, we found haplotypes shared between the Fulani and Arabic‐speaking Baggara, supporting the theory of Baggarization, which explains the recent adaptation of Arabic‐speaking nomads in the Sahel region through contact with autochthonous sub‐Saharan populations.
Conclusions
Based on various genetic and archaeological evidence pertaining to the Sahel, we suggest that the idea of a bidirectional Sahelian corridor is valid, but that pastoralists made a more important contribution to its population structure. It is also possible that agropastoralists diverged into farmers and pastoralists in the early stages of formation of the Sahelian gene pool.