Graeber / Wengrow 90-1: "In Europe, between 25,000 and 12,000 years ago public works were already a feature of human habitation across an area reaching from Krakow to Kiev. Along this transect of the glacial fringe, remains of impressive circular structures have been found that are clearly distinguishable from ordinary camp-dwellings in their scale (the largest were over thirty-nine feet in diameter), permanence, aesthetic qualities and prominent locations in the Pleistocene landscape [...] the kinds of structures we've been describing can only have been considered public works, involving sophisticated design and the coordination of labor on an impressive scale"
"apparent proof" that "hunter-gatherer societies had evolved institutions to support major public works, projects, and monumental constructions, and thus had a complex social hierarchy prior to their adoption of farming" (Acemoglu and Robinson quoted here)
see also Göbekli Tepe, 89-90