The case for an unprecedented penetration of life mechanisms into the politics of Western modernity has been a cornerstone of 20th-century social theory. Working with and beyond Foucault, this article challenges established views about the history of biopower by focusing on ancient medical writings and practices of corporeal permeability. Through an analysis of three Roman institutions: a) bathing; b) urban architecture; and c) the military, it shows that technologies aimed at fostering and regulating life did exist in classical antiquity at (...) the population scale. The article highlights zones of indistinction between natural and political processes, zoē and bíos, that are not captured by a view of destructive incorporation of or over life by sovereign power. In conclusion, the article discusses the theoretical potential of this historical evidence for contemporary debates on ‘affirmative biopolitics’ and ‘environmental biopower’. (shrink)