A surprising aspect of this analysis is the positioning of Ighrem Arabs between Boutroch Amazigh and half of the Agadir Arabs along PC2. This was confirmed by Structure analysis9 of 16,000 randomly chosen autosomal SNPs assuming admixture of two ancestral populations (Fig. 2b), which indicates that Ighrem residents tend to be a mixture, while most Amazigh are derived from one population, and only a handful of Agadir Arabs represent the other. There has thus likely been considerable admixture between these two groups over an extended period of time, possibly with movement of Arabs from other locations into Agadir recently. A slight shift of Ighrem Arabs toward the Amazigh pole of PC2, relative to Agadir Arabs, would also be consistent with some genetic exchange between the villages over 50 generations. Further sampling of villages in the region may reveal subtle population structure across southern Morocco10–13.
