The genomic echoes of the last Green Sahara on the Fulani and Sahelian people

Abstract

The population history of the Sahara/Sahelian belt is understudied, despite previous work highlighting complex dynamics.^{1,2,3,4,5,6,7} The Sahelian Fulani, i.e., the largest nomadic pastoral population in the world,⁸ represent an interesting case because they show a non-negligible proportion of an Eurasian genetic component, usually explained by recent admixture with northern Africans.^{1,2,5,6,7,9,10,11,12} Nevertheless, their origins are largely unknown, although several hypotheses have been proposed, including a possible link to ancient peoples settled in the Sahara during its last humid phase (Green Sahara, 12,000-5,000 years before present [BP]).^13,14,15 To shed light about the Fulani ancient genetic roots, we produced 23 high-coverage (30×) whole genomes from Fulani individuals from 8 Sahelian countries, plus 17 samples from other African groups and 3 from Europeans as controls, for a total of 43 new whole genomes. These data have been compared with 814 published modern whole genomes^2,16,17,18 and with relevant published ancient sequences (> 1,800 samples).¹⁹ These analyses showed some evidence that the non-sub-Saharan genetic ancestry component of the Fulani might have also been shaped by older events,^1,5,6 possibly tracing the Fulani origins to unsampled ancient Green Saharan population(s). The joint analysis of modern and ancient samples allowed us to shed light on the genetic ancestry composition of such ancient Saharans, suggesting a similarity with Late Neolithic Moroccans and possibly pointing to a link with the spread of cattle herding. We also identified two different Fulani clusters whose admixture pattern may be informative about the historical Fulani movements and their later involvement in the western African empires.

Keywords: Africa; Fulani; Fulbe; Green Sahara; Sahel; evolutionary genetics; population genomics; whole genomes.