Heterogeneity in palaeolithic population continuity and neolithic expansion in North Africa

North Africa is located at the crossroads of the Mediterranean Sea, the Middle East, and the Sahara Desert. Extensive migrations and gene flow in the region have shaped many different cultures and ancestral genetic components through time [1–6]. DNA data from ancient Moroccan sites [7, 8] has recently shed some light to the population continuity-versus-replacement debate, i.e., the question of whether current North African populations descend from Palaeolithic groups or, on the contrary, subsequent migrations swept away all pre-existing genetic signal in the region. In the present study, we analyze 21 complete North African genomes and compare them with extant and ancient genome data in order to address the demographic continuity-versus-replacement debate, to assess whether these demographic events were homogeneous (including Berber and Arabic-speaking groups), and to explore the effect of Neolithization and posterior migration waves. The North African genetic pool is defined as a melting pot of genetic components, including an endemic North African Epipalaeolithic component at low frequency that forms a declining gradient from Western to Eastern North Africa. This scenario is consistent with Neolithization having shaped most of the current genetic variation in the region when compared to posterior back-to-North-Africa migration waves such as the Arabization. A common and distinct genetic history of the region is shown, with internal different proportions of genetic components owing to differential admixture with surrounding groups as well as to genetic drift due to isolation and endogamy in certain populations.Serra-Vidal et al. report that human North African genomes exhibit traces of continuity from Paleolithic times in a decreasing pattern from West to East. Neolithic and posterior migrations did not erase the pre-existing Paleolithic substrate. The demographic impact of Neolithization was larger than posterior migrations, such as Arabization.This work was supported by the Spanish Agencia Estatal de Investigación (MINEICO, AEI) and Fondo Europeo de Desarollo Regional (FEDER) grants CGL-2013-44351-P and CGL2016-75389-P, the “Unidad de Excelencia Maria de Maeztu” MDM2014-0370, and Agència de Gestió d’Ajuts Universitaris i de la Recerca (grant 2014SGR866). G.S.V. was supported by an FI (2017FI_B2 00010) scholarship awarded by the Generalitat de Catalunya