Entwined African and Asian Genetic Roots of Medieval Peoples of the Swahili Coast

Abstract

The urban peoples of the Swahili coast traded across eastern Africa and the Indian Ocean and were among the first sub-Saharan practitioners of Islam [1, 2]. The extent to which these early interactions between Africans and non-Africans were accompanied by genetic exchange remains unknown. We report ancient DNA data for 80 individuals from six medieval and early modern (1250-1800 CE) coastal towns and an inland town postdating 1650 CE. Many coastal individuals had over half their DNA from primarily female African ancestors, with large proportions and occasionally more than half from Asian ancestors. The Asian ancestry included both Persian and Indian-associated components, with eighty to ninety percent from Persian males. Peoples of African and Asian origins began to mix by about 1000 CE, coinciding with large-scale adoption of Islam. Before about 1500 CE, the Southwest Asian ancestry was mainly Persian-related, consistent with the narrative of the Kilwa Chronicle, the oldest history told by people of the Swahili coast [3]. After this time, the sources became increasingly Arabian, consistent with evidence of growing interactions with southern Arabia [4]. Subsequent interactions with Asians and Africans further changed the ancestry of Swahili coast people relative to the medieval individuals whose DNA we sequenced.