The Fulani people, one of the most important pastoralist groups in sub-Saharan Africa, are still largely underrepresented in population genomic research. They speak a Niger-Congo language called Fulfulde or Pulaar and live in scattered locations across the Sahel/Savannah belt, from the Atlantic Ocean to Lake Chad. According to historical records, their ancestors spread from Futa Toro in the Middle Senegal Valley to Futa-Jallon in Guinea and then eastward into the Sahel belt over the past 1,500 years. However, the earlier history of this traditionally pastoral population has not been well studied. To uncover the genetic structure and ancestry of this widespread population, we gathered genome-wide genotype data from 460 individuals across 18 local Fulani populations, along with comparative data from both modern and ancient worldwide populations. This represents a comprehensive geographically wide-scaled genome-wide study of the Fulani. We revealed a genetic component closely associated with all local Fulani populations, suggesting a shared ancestral component possibly linked to the beginning of African pastoralism in the Green Sahara. Comparison to ancient DNA results also identified the presence of an ancient Iberomaurusian-associated component across all Fulani groups, providing additional insights into their deep genetic history. Additionally, our genetic data indicate a later Fulani expansion from the western to the eastern Sahel, characterized by a clinal pattern and admixture with several other African populations north of the equator.

• Keywords
• Africa, Fulani, Sahel, admixture, ancient DNA, genomics, migration, population structure,
• MeSH
• Black People * genetics   MeSH
• Ethnicity * genetics   MeSH
• Genome, Human MeSH
• Genotype MeSH
• Polymorphism, Single Nucleotide genetics   MeSH
• Humans MeSH
• Human Migration * history   MeSH
• Genetics, Population * MeSH
• Central African People MeSH
• East African People MeSH
• West African People MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Geographicals
• Africa South of the Sahara MeSH

African populations remain underrepresented in studies of human genetic diversity, despite a growing interest in understanding how they have adapted to the diverse environments they live in. In particular, understanding the genetic basis of immune adaptation to pathogens is of paramount importance in a continent such as Africa, where the burden of infectious diseases is a major public health challenge. In this study, we investigated the molecular variation of four Human Leukocyte Antigens (HLA) class II genes (DRB1, DQA1, DQB1 and DPB1), directly involved in the immune response to parasitic infections, in more than 1000 individuals from 23 populations across North, East, Central and West Africa. By analyzing the HLA molecular diversity of these populations in relation to various geographical, cultural and environmental factors, we identified divergent genetic profiles for several (semi-)nomadic populations of the Sahel belt as a signature of their unique demography. In addition, we observed significant genetic structuring supporting both substantial geographic and linguistic differentiations within West Africa. Furthermore, neutrality tests suggest balancing selection has been shaping the diversity of these four HLA class II genes, which is consistent with molecular comparisons between HLA genes and their orthologs in chimpanzees (Patr). However, the most striking observation comes from linear modeling, demonstrating that the prevalence of Plasmodium falciparum, the primary pathogen of malaria in Africa, significantly explains a large proportion of the nucleotide diversity observed at the DPB1 gene. DPB1*01:01, a highly frequent allele in Burkinabé populations, is identified as a potential protective allele against malaria, suggesting that strong pathogen-driven positive selection at this gene has shaped HLA variation in Africa. Additionally, two low-frequency DRB1 alleles, DRB1*08:06 and DRB1*11:02, also show significant associations with P. falciparum prevalence, supporting resistance to malaria is determined by multigenic and/or multiallelic combinations rather than single allele effects.

• Keywords
• Africa, HLA, human molecular diversity, malaria, pathogen‐driven selection, plasmodium falciparum,
• Publication type
• Journal Article MeSH

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.

• Keywords
• Africa, Sahel/Savannah belt, archaeogenetics, pastoralism, population genetics, selection,
• MeSH
• Archaeology MeSH
• Humans MeSH
• Polymorphism, Genetic * MeSH
• Genetics, Population * MeSH
• Cattle MeSH
• Agriculture MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Cattle MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH
• Geographicals
• Africa MeSH

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 10 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.

• Keywords
• CNR1 gene, Africa, admixture, camel herders, pastoralists, population structure, selection,
• MeSH
• Black People MeSH
• Ethnicity genetics   MeSH
• Haplotypes MeSH
• Lactase genetics   MeSH
• Humans MeSH
• Genetics, Population * MeSH
• Gene Flow * MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Lactase MeSH

BACKGROUND: Human population history in the Holocene was profoundly impacted by changes in lifestyle following the invention and adoption of food-production practices. These changes triggered significant increases in population sizes and expansions over large distances. Here we investigate the population history of the Fulani, a pastoral population extending throughout the African Sahel/Savannah belt. RESULTS: Based on genome-wide analyses we propose that ancestors of the Fulani population experienced admixture between a West African group and a group carrying both European and North African ancestries. This admixture was likely coupled with newly adopted herding practices, as it resulted in signatures of genetic adaptation in contemporary Fulani genomes, including the control element of the LCT gene enabling carriers to digest lactose throughout their lives. The lactase persistence (LP) trait in the Fulani is conferred by the presence of the allele T-13910, which is also present at high frequencies in Europe. We establish that the T-13910 LP allele in Fulani individuals analysed in this study lies on a European haplotype background thus excluding parallel convergent evolution. We furthermore directly link the T-13910 haplotype with the Lactase Persistence phenotype through a Genome Wide Association study (GWAS) and identify another genomic region in the vicinity of the SPRY2 gene associated with glycaemic measurements after lactose intake. CONCLUSIONS: Our findings suggest that Eurasian admixture and the European LP allele was introduced into the Fulani through contact with a North African population/s. We furthermore confirm the link between the lactose digestion phenotype in the Fulani to the MCM6/LCT locus by reporting the first GWAS of the lactase persistence trait. We also explored other signals of recent adaptation in the Fulani and identified additional candidates for selection to adapt to herding life-styles.

• Keywords
• Adaptive gene-flow, Fulani people, GWAS, Lactase persistence, Pastoralism,
• MeSH
• Genome-Wide Association Study MeSH
• Black People genetics   MeSH
• Lactase genetics   MeSH
• Humans MeSH
• Evolution, Molecular MeSH
• Transients and Migrants MeSH
• Gene Flow MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Geographicals
• Europe MeSH
• Names of Substances
• Lactase MeSH