Is Aesthetic Evolution Possible in Birds? —Conceptual Considerations

Abstract The adaptive mate choice theory is believed to provide a general explanation of sexual selection. Females are thought to choose males based on direct benefits or because they have perceivably good genes based on visual indicators of male quality, involving adaptive qualities acted on by natural selection in the current environment. However, a recent hypothesis, called “Beauty Happens” has been proposed based on Darwin's “Really Dangerous Idea,” an idea that has been criticised, to explain sexual selection in animals, including human beings. Accordingly, it has garnered widespread attention and evoked controversial debate. Here, I review the Beauty Happens hypothesis and clarify the arguments that focus on the sexual autonomy and aesthetic perception of females. I found that, in the case of sexually dimorphic birds, unambiguous evidence is absent in support of the adaptive mate choice theory. Although the Beauty Happens hypothesis is logically feasible, aesthetic perception could possibly evolve and develop on the basis of sexual autonomy and resource-independence in females. Therefore, aesthetic radiation among females may lead to beauty radiation in males, and female mate choice as a selection process may act independently of natural selection, favouring good-to-pass-on genes rather than good genes. However, the Beauty Happens hypothesis seems to be more applicable when explaining the behaviour of sexually dimorphic birds than other animal taxa. I suggest that the mechanisms of female mate choice and intrasexual competition in males may lead to biological evolution, depending on the degree of autonomy of females in different animal species.