The author attempts to evaluate a model adaptive ritual in a sample of sub-Saharan African groups in which ritual cosmetic decoration acts as a costly signal of coalition membership and sexual fitness. The prediction is that, according to sexual selection theory, male ritual signalling will be more extreme in societies with more inter-male competition, while severity of female ritual signalling will be associated with greater need to establish costs that protect against the danger of free riders. The prediction is supported by two tests which proxy inter-male competition by degree of polygny, and threat of free riders by population density.