So long as sustainability represents the attempt to pacify the relationship between societies and their natural environments, the concept must remain attentive to any findings about the character of such relation. In this regard, the rise of the Anthropocene cannot be ignored by environmental sociologists if a realistic understanding of sustainability is to be produced. The Anthropocene is a scientific notion, grounded on geology and Earth-system science, that plausibly suggests that human beings have colonized nature in a degree that has irreversibly altered the functioning of planetary systems. As a result, social and natural systems have become "coupled". This paper tries to elucidate the consequences that an "Anthropocenic turn" would have for sustainability studies. To such end, it will explore the related notions of hybridity and relational agency as key aspects of a renewed view of nature. Correspondingly, it argues that cultivated capital (rather than natural or manmade) must be the most important unit for measuring sustainability and devising sustainable policies in a postnatural age.