It’s Not about Him: Mismeasuring ‘Good Genes’ in Sexual Selection

What explains preferences for elaborate ornamentation in animals? The default answer remains that the prettiest males have the best genes. If mating signals predict good genes, mating preferences evolve because attractive mates yield additive genetic benefits through offspring viability, thereby maximizing chooser fitness. Across disciplines, studies claim ‘good genes’ without measuring mating preferences, measuring offspring viability, distinguishing between additive and nonadditive benefits, or controlling for manipulation of chooser investment. Crucially, studies continue to assert benefits to choosers purely based on signal costs to signalers. A focus on fitness outcomes for choosers suggests that ‘good genes’ are insufficient to explain the evolution of mate choice or of sexual ornamentation.