Prehistoric population structure associated with the transition to an agricultural lifestyle in Europe remains contentious. Population-genomic data from eleven Scandinavian Stone-Age human remains suggest that hunter-gatherers had lower genetic diversity than farmers. Despite their close geographical proximity, the genetic differentiation between the two Stone-Age groups was greater than that observed among extant European populations. Additionally, the Scandinavian Neolithic farmers exhibited a greater degree of hunter-gatherer-related admixture than that of the Tyrolean Iceman, who also originated from a farming context. In contrast, Scandinavian hunter-gatherers displayed no significant evidence of introgression from farmers. Our findings suggest that Stone-Age foraging groups were historically in low numbers, likely due to oscillating living conditions or restricted carrying-capacity, and that they were partially incorporated into expanding farming groups.