Genetic Structure of the Western and Eastern African Sahel/Savannah Belt and the Role of Nomadic Pastoralists as Inferred from the Variation of D-Loop Mitochondrial DNA Sequences

Čížková, Martina; Munclinger, Pavel; Diallo, Mame Yoro; Kulichová, Iva Kulichová; Mokhtar, Mohammed G.; Dème, Alioune; Pereira, Luı́sa; Černý, Viktor

doi:10.1353/hub.2017.0035

Cited by 3 publications

(11 citation statements)

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“…Among all studied Sahelian populations, this recent migrant population has a strong shared ancestry with the Middle Eastern groups and no or very little gene-flow with African groups. In agreement, the Rashaayda Arab population has mtDNA haplogroups mostly present among only Middle Eastern populations, such as R0a2c and J1b ( Čížková et al 2017 ; Priehodová et al 2017 ), and in all genetic results are striking outliers among African populations due to genetic drift or isolation. We found strong genetic affinities between this population and Arabic-speaking people living in Saudi Arabia ( supplementary figs.…”

Section: Discussionsupporting

confidence: 57%

“…There is, however, an asymmetry in maternal gene-flow between sedentary farmers and Fulani pastoralists in the western part and between sedentary farmers and Arabic pastoralists in the eastern part of the Sahel belt ( Černý et al 2018 ). While the Fulani continually loose inherent mitochondrial-DNA (mtDNA) lineages (Fulani women usually marry neighboring farmers), Arab groups, who originally arrived from the Arabian Peninsula, more often accepted women from local sub-Saharan populations into their communities ( Čížková et al 2017 ). This is also evident from the occurrences of sub-Saharan mtDNA haplotypes in Arabic-speaking populations in the Sahel/Savannah belt (such as the Baggara, Shuwa, and Abbala), while these haplotypes are not found in Arabian populations from founding populations in the Arabian Peninsula ( Priehodová et al 2017 ).…”

Section: Introductionmentioning

confidence: 99%

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Demographic and Selection Histories of Populations Across the Sahel/Savannah Belt

Fortes-Lima

Tříska

Čížková

et al. 2022

Molecular Biology and Evolution

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The Sahel/Savannah belt harbors diverse populations with different demographic histories and different subsistence patterns. However, populations from this large African region are notably under-represented in genomic research. To investigate the population structure and adaptation history of populations from the Sahel/Savannah space, we generated dense genome-wide genotype data of 327 individuals—comprising 14 ethnolinguistic groups, including ten previously unsampled populations. Our results highlight fine-scale population structure and complex patterns of admixture, particularly in Fulani groups and Arabic-speaking populations. Among all studied Sahelian populations, only the Rashaayda Arabic-speaking population from eastern Sudan shows a lack of gene flow from African groups, which is consistent with the short history of this population in the African continent. They are recent migrants from Saudi Arabia with evidence of strong genetic isolation during the last few generations and a strong demographic bottleneck. This population also presents a strong selection signal in a genomic region around the CNR1 gene associated with substance dependence and chronic stress. In Western Sahelian populations, signatures of selection were detected in several other genetic regions, including pathways associated with lactase persistence, immune response, and malaria resistance. Taken together, these findings refine our current knowledge of genetic diversity, population structure, migration, admixture and adaptation of human populations in the Sahel/Savannah belt and contribute to our understanding of human history and health.

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Section: Discussionsupporting

confidence: 57%

Section: Introductionmentioning

confidence: 99%

Demographic and Selection Histories of Populations Across the Sahel/Savannah Belt

Fortes-Lima

Tříska

Čížková

et al. 2022

Molecular Biology and Evolution

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“…Genetic analyses generally revealed weak population structure, with most of the variation found within groups rather than between groups ( Čížková et al 2017 ; Nováčková et al 2020 ; Diallo et al 2022 ; Fortes-Lima et al 2022 ). Depending on subsistence strategy, different distributions of uniparental markers have been observed in the Sahel.…”

Section: Pervasive Admixture In Africa During the Past 10000 Yearsmentioning

confidence: 99%

Evolutionary Genetics and Admixture in African Populations

Pfennig

Petersen

Kachambwa

et al. 2023

Genome Biology and Evolution

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As the ancestral homeland of our species, Africa contains elevated levels of genetic diversity and substantial population structure. Importantly, African genomes are heterogeneous: they contain mixtures of multiple ancestries, each of which have experienced different evolutionary histories. In this review, we view population genetics through the lens of admixture, highlighting how multiple demographic events have shaped African genomes. Each of these historical vignettes paints a recurring picture of population divergence followed by secondary contact. First, we give a brief overview of African genetic variation and examine deep population structure within Africa, including evidence of ancient introgression from archaic “ghost” populations. Second, we describe the genetic legacies of admixture events that have occurred during the past 10,000 years. This includes gene flow between different click-speaking Khoe-San populations, the stepwise spread of pastoralism from eastern to southern Africa, multiple migrations of Bantu speakers across the continent, as well as admixture from the Middle East and Europe into the Sahel region and North Africa. Furthermore, the genomic signatures of more recent admixture can be found in the Cape Peninsula and throughout the African diaspora. Third, we highlight how natural selection has shaped patterns of genetic variation across the continent, noting that gene flow provides a potent source of adaptive variation and that selective pressures vary across Africa. Finally, we explore the biomedical implications of African population genetic structure on health and disease and call for more ethically conducted studies of African genetic variation.

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“…Research into uniparental genetic systems across the Sahelian populations suggests that there might be an asymmetric gene flow between the pastoralists and the farmers on the level of mtDNA, i.e., the part of genome transmitted along the maternal line [ 55 ]. In the eastern part of the Sahel, this asymmetric gene flow has been stronger in the direction from the agricultural to the pastoralist populations, while in the western part of the Sahel it was less intense in that direction and clearly stronger in the opposite direction, i.e., from the pastoralists to the farmers.…”

Section: The Contribution Of Population Genetics To Disentangling Hum...mentioning

confidence: 99%

“…In the eastern part of the Sahel, this asymmetric gene flow has been stronger in the direction from the agricultural to the pastoralist populations, while in the western part of the Sahel it was less intense in that direction and clearly stronger in the opposite direction, i.e., from the pastoralists to the farmers. This indicates certain specific features of population dynamics within the populations of both subsistence strategies in the western and eastern Sahel, exemplified by the Fulani and the Arabic-speaking communities, respectively [ 55 ]. Another study [ 34 ] suggests, based on mtDNA and Y-chromosome data, that genetic distances among the local populations of farmers might significantly correlate with the geographic but not the linguistic distances.…”

Section: The Contribution Of Population Genetics To Disentangling Hum...mentioning

confidence: 99%

A Population Genetic Perspective on Subsistence Systems in the Sahel/Savannah Belt of Africa and the Historical Role of Pastoralism

Černý

Priehodová

Fortes-Lima

2023

Genes

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This review focuses on the Sahel/Savannah belt, a large region of Africa where two alternative subsistence systems (pastoralism and agriculture), nowadays, interact. It is a long-standing question whether the pastoralists became isolated here from other populations after cattle began to spread into Africa (~8 thousand years ago, kya) or, rather, began to merge with other populations, such as agropastoralists, after the domestication of sorghum and pearl millet (~5 kya) and with the subsequent spread of agriculture. If we look at lactase persistence, a trait closely associated with pastoral lifestyle, we see that its variants in current pastoralists distinguish them from their farmer neighbours. Most other (mostly neutral) genetic polymorphisms do not, however, indicate such clear differentiation between these groups; they suggest a common origin and/or an extensive gene flow. Genetic affinity and ecological symbiosis between the two subsistence systems can help us better understand the population history of this African region. In this review, we show that genomic datasets of modern Sahel/Savannah belt populations properly collected in local populations can complement the still insufficient archaeological research of this region, especially when dealing with the prehistory of mobile populations with perishable material culture and therefore precarious archaeological visibility.

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Genetic Structure of the Western and Eastern African Sahel/Savannah Belt and the Role of Nomadic Pastoralists as Inferred from the Variation of D-Loop Mitochondrial DNA Sequences

Cited by 3 publications

References 0 publications

Demographic and Selection Histories of Populations Across the Sahel/Savannah Belt

Demographic and Selection Histories of Populations Across the Sahel/Savannah Belt

Evolutionary Genetics and Admixture in African Populations

A Population Genetic Perspective on Subsistence Systems in the Sahel/Savannah Belt of Africa and the Historical Role of Pastoralism

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