Abstract: The functioning of animal as well as human societies fundamentally relies on cooperation. Yet, defection is often favorable for the selﬁsh individual, and social dilemmas arise. Selection by individuals’ ﬁtness, usually the basic driving force of evolution, quickly eliminates cooperators. However, evolution is also governed by ﬂuctuations that can be of greater importance than ﬁtness differences, and can render evolution effectively neutral. Here, we investigate the effects of selection versus ﬂuctuations in social dilemmas.