Settlements incorporating large-scale human aggregations are a well-documented but poorly understood phenomenon across late prehistoric Europe. The authors’ research examines the origins and trajectory of such aggregations through isotope analysis of human skeletal remains from the mega-site of Marroquíes in Jaén, Spain. The results indicate that eight per cent of 115 sampled individuals are of non-local origin. These individuals received mortuary treatments indistinguishable from those of locals, suggesting their incorporation into pre-existing social networks in both life and death. This research contributes to our understanding of the extent and patterning of human mobility, which underlies the emergence of late prehistoric mega-sites in Europe.