Sexual selection favors traits that increase mating and, thus, reproductive success. Some scholars have suggested that intrasexual selection driven by contest competition has shaped human male aggression. If this is the case, one testable hypothesis is that beliefs and behavior related to male aggression should be more prevalent in societies where the intensity and strength of sexual selection is higher, as measured by factors such as: (a) the presence and scope of polygyny; (b) the number of same-sex competitors relative to potential mates; and, (c) the amount of effort males have available to allocate to mating. Using mixed-effect linear regression models with data from 78 societies from the Standard Cross-Cultural Sample, we found mixed support for the hypothesis using individual variables related to male aggression, but strong support when using a composite measure of male ‘aggressiveness’. We ruled out some potential alternative explanations by controlling for spatial autocorrelation, and confounding variables such as political complexity and warfare.