Sexiness, Individual Condition, and Species Identity: The Information Signaled by Ornaments and Assessed by Choosing Females

Biologists have long debated the evolution of animal ornamentation via female choice. Much of the discussion of ornament evolution has focused on three hypotheses: the species recognition hypothesis, the indicator trait hypothesis, and the runaway sexual selection hypothesis. These models of sexual selection have generally been considered in isolation, with each assessed as a potential complete explanation for ornament evolution. In fact, any choosing female potentially benefits by assessing three distinct characteristics of a prospective mate-species identity, individual condition, and sexiness-such that there can be no comprehensive explanation of ornamentation without consideration of the need for females to assess these three key attributes of males. There is no logical basis for advocating for the importance of one of these classes of information over another. Consideration that all three assessments of prospective males work in tandem to shape the evolution of female preferences for male ornaments leads to a better understanding of the diversity of ornamentation within and among animal species.