Next to natural selection, sexual selection is the most powerful force driving evolution. A cluster of recent papers about sex and evolution are the focus of this Select. New work suggests that the evolution of sex chromosomes is a potent mechanism for resolving sexual conflict and for driving speciation. Furthermore, another study suggests that the mechanism by which the sex of the offspring of a species is determined has a profound impact on the evolutionary potential of that species. Finally, pathogens that change the sex ratio of a species can be detected in museum specimens, providing historic clues about recent population changes.