I'm happy to report that I have a new paper out with Pablo Lozano and Sergey Gavrilets in which we present a model for the emergence of hierarchies compatible with cooperation. A few years ago, in an experimental paper we found that hierarchy (understood as privileged access to jointly generated resources) hinders cooperation among human subjects (although when hierarchy was not linear but in groups this did not occur, see subsequent paper). With the model we have just introduced, we show that when hierarchies are dynamical and can evolve through fights among the individuals, much like in primate societies in general, then a large fraction of people still cooperate. Note that this is not good news, in the sense that what happens typically is that the society splits in an upper class and a lower class, with the former exploiting the latter that has to cooperate in order to have a chance to earn a living. Ugly, but kind of realistic. We believe that this model is a relevant step to understand how egalitarian societies could evolve to hierarchical, class-split ones, highlighting the importance of dynamical hierarchies and suggesting fighting as a possible mechanism for that dynamics.