Assortative mechanisms can overcome tragedies of the commons that otherwise result in dilemma situations. Assortativity criteria include genetics, preferences, locations and actions, usually presuming an exogenously fixed matching mechanism. Here, we endogenize the matching process with the aim of investigating how assortativity itself, jointly with cooperation, is driven by evolution. Our main finding is that only full-or-null assortativities turn out to be long-run stable, their relative stabilities depending on the exact incentive structure of the underlying social dilemma. The resulting social (...) loss is evaluated for general classes of dilemma games, thus quantifying to what extent tragedy of the commons may be endogenously overcome. (shrink)