Laser ablation strontium isotope analysis of human remains from Harlaa and Sofi, eastern Ethiopia, and the implications for Islamisation and mobility

The ancient city of Harlaa in eastern Ethiopia was occupied between the mid-6th and early 15th centuries AD and played a significant role as a trading centre with links internationally. Besides goods, these trade links also served in spreading cultural and religious ideas between continents, including Islamic traditions which became prevalent in Ethiopia during this time. Here, we present the first strontium isotope analysis of human remains from an Islamic site in Ethiopia. Results show that individuals buried following Islamic traditions include people born and raised both in Harlaa itself and also in rural communities from the surrounding hinterland, revealing a resident local Muslim community and potential co-existence of Muslim and non-Muslim individuals across economic sectors. The repeatability of results produced by laser ablation in human teeth sampled multiple times around the tooth cusp is also confirmed, although small differences between simultaneously-forming molar elements from a single individual were observed.