Evolution of female mate choice based on male age: Are older males better mates?

Many empirical studies suggest that females often prefer to mate with older males. It is generally assumed that females prefer older males because old er males are of higher genetic quality. We used a viability-based simulatio n model to determine whether female preference for older mates is more like ly to evolve than female preference for younger mates when males provide on ly sperm to females The results of our simulations suggest that female pref erence for young and intermediate age mates is more likely to evolve than a strong preference for older mates, and that female preference based on mal e age will not evolve if there is a cost associated with the preference. Th erefore, based on the results of our model, female preferences for older ma tes cannot be explained by 'good genes' models of sexual selection. A compa rison of our results with those of a previously published model suggest tha t whether female preference for older males can be explained by 'good genes ' models of sexual selection depends on age-specific survival probabilities . When juvenile survival is high and adult survival is low, older males hav e higher mean viability than younger males. As a result, female preference for older males will evolve. In contrast, when juvenile survival is low and adult survival is high, mean viability does not differ among males of diff erent ages. Therefore, female preference for older males is unlikely to evo lve. The importance of age-specific survival rates in determining the impor tance of a 'good genes' process suggests that future studies of sexual sele ction should consider potential effects of life-history variation.