What guides ownership intuitions, thoughts of the form “this thing x belongs to person A” ? Psychologists generally assume that human minds possess an implicit ownership theory, from which ownership intuitions are derived. But this mental theory is mostly an ad hoc stipulation. A more plausible, deflationary interpretation is that ownership intuitions result from two cognitive systems, geared to managing a) competitive acquisition (Hawk-dove-bourgeois interactions) and b) mutualistic cooperation, both of which are documented in an abundant evolutionary literature. Survey studies suggest that, in agreement with a competition-cooperation perspective, levels of cooperation expectations influence ownership intuitions in everyday contexts.