Medieval Ibiza was far from a quiet Mediterranean backwater. New DNA evidence shows that the island was part of a dynamic world linking Europe, North Africa and even the Sahel zone, south of Sahara. An international research team led from the Centre for Palaeogenetics (CPG), a joint venture between Stockholm University and the Swedish Museum of Natural History, has revealed that its population was remarkably diverse, connected to Europe, North Africa, and sub-Saharan Africa through trade, migration, and social networks. The study is published in Nature Communications.
By analysing ancient DNA from 13 individuals buried in a tenth- to twelfth-century Islamic cemetery, the researchers found a wide spectrum of genetic ancestries, ranging from predominantly European to predominantly North African. This reflects varying degrees of mixing following the Muslim conquest of Ibiza in 902 CE. Historical sources describe two major demographic waves shaping the island: an initial settlement linked to the Umayyad expansion, and a later influx connected to the Almoravid conquest in the early twelfth century.
Two individuals carried sub-Saharan African ancestry, one tracing back to present-day Senegambia, the other to southern Chad, providing biological evidence of trans-Saharan military and/or slave networks recorded in medieval Arabic texts.
"These genomes show that people from both western and central Sahel became part of communities in Islamic Iberia," says Ricardo Rodríguez-Varela, researcher at the Department of Archaeology and Classical Studies at Stockholm University and lead author of the study. "This is direct genetic evidence of the long-distance networks reaching the Sahel, as described in historical sources."
Using advanced genomic techniques, including genotype imputation and haplotype-based local ancestry analysis, the team estimated that North African gene flow into Ibiza began only two to seven generations earlier. This places the main admixture event in the late ninth century CE.
"These genomes capture the moment when the Islamic world and the Christian societies of Iberia began to reshape each other," says Anders Götherström, senior author of the study and leader of the archaeogenetics research group at the Centre for Palaeogenetics. "With ancient DNA we can begin to see how these large historical processes unfolded in the lives of real people."
The study also screened for infectious agents. One individual was infected with Mycobacterium leprae, the bacterium responsible for leprosy, marking the first genetically confirmed case from medieval Islamic Iberia. His burial conformed to standard Islamic practices, with no signs of exclusion.
"There is no evidence in the burial context that he was treated differently from others, a pattern also reported in contemporaneous Christian communities," says Zoé Pochon, researcher at the Department of Archaeology and Classical Studies at Stockholm University, co-author and metagenomics specialist.
Phylogenetic analysis places the M. leprae genome near the base of a lineage found across Europe between the seventh and thirteenth centuries, alongside an early-diverging genome from Italy. This suggests that Ibiza was part of wider epidemiological networks, and highlight the potential dispersal of leprosy lineage from the Mediterranean into Europe.
