Sahelian pastoralism from the perspective of variants associated with lactase persistence

Abstract

Objectives: Archeological evidence shows that first nomadic pastoralists came to the African Sahel from northeastern Sahara, where milking is reported by 7.5 ka. A second wave of pastoralists arrived with the expansion of Arabic tribes in 7th-14th century CE. All Sahelian pastoralists depend on milk production but genetic diversity underlying their lactase persistence (LP) is poorly understood. Materials and methods: We investigated SNP variants associated with LP in 1,241 individuals from 29 mostly pastoralist populations in the Sahel. Then, we analyzed six SNPs in the neighboring fragment (419 kb) in the Fulani and Tuareg with the −13910*T mutation, reconstructed haplotypes, and calculated expansion age and growth rate of this variant. Results: Our results reveal a geographic localization of two different LP variants in the Sahel: −13910*T west of Lake Chad (Fulani and Tuareg pastoralists) and −13915*G east of there (mostly Arabic-speaking pastoralists). We show that −13910*T has a more diversified haplotype background among the Fulani than among the Tuareg and that the age estimate for expansion of this variant among the Fulani (8.5 ka) corresponds to introduction of cattle to the area.

Demographic history was a formative mechanism of the genetic structure for the taste receptor TAS2R16 in human populations inhabiting Africa's Sahel/Savannah Belt

“…This finding seems to be consistent with the difference between the mobility of these lifestyle groups, and therefore also with the limited gene flow between them . This result contrasts with the findings of previous studies on Sahelian populations that analyzed uniparental genetic systems (Černý et al, 2011;Novác ˇková et al, 2020), markers associated with lactase persistence (Priehodová et al, 2020;Vicente et al, 2019), and NAT2 sequences (Podgorná et al, 2015), all of which indicated a relatively high correspondence between subsistence mode and genetic and even phenotypic (Kleisner et al, 2019) structure of populations across the African Sahel/Savannah belt. The present study supports the notion that genetic differentiation between populations at TAS2R16 does not correspond to specific foodproduction strategies; instead it suggests that TAS2R16 variation reflects a geographic structure that was mainly shaped by neutral, demographic processes (Campbell et al, 2014b;Kim et al, 2005;Soranzo et al, 2005).…”

Circum-Saharan Prehistory through the Lens of mtDNA Diversity

“…The first event is genetically dated to ~1828 years ago and the second one to ~302 years ago, whereby it seems that the admixture involved a group related to southwestern Europeans. Moreover, the geographical distribution of lactase persistence variants in the Sahel/Savannah belt shows clear differences between the pastoralists in the east (mostly Arabs harboring variant −13,915 × G) and the west (mostly Fulani harboring variant −13,910 × T) [ 25 ]. In fact, a boundary between the western and eastern Sahelian genetic spaces lies somewhere near the Lake Chad Basin, as attested not only by lactase persistence but also by a genome-wide SNP study [ 26 ].…”

A Human Security Angle of Conflicts: The Case of Farmer–Herder Conflict in Ghana

“…Like other West African countries such as Nigeria (Chiamogu and Chiamogu 2020), Cameroon (Awazi and Avana-Tientcheu 2020) and Mali (Priehodová et al 2020), Ghana has for some time now been plagued with farmer-herder conflicts (Agyemang 2017;Tonah 2006;Otu, Impraim, and Twumhene 2020) with profound consequences for the country. Not much has been done about the human security costs of these destructive conflicts, creating a scholarly gap in Ghana and the need for an empirical study of this nature.…”