Sexual dimorphism and sexual selection: a unified analysis

Cyrus Chu, Academia Sinica
Ronald Lee, University of California, Berkeley

We develop a life history model with two sexes, and study the optimal energy allocation strategy of males and females. We join others in suggesting that the origin of sexual dimorphism and sexual selection is the difference between male and female reproduction costs. Due to this assumed cost difference, the resulting Bellman equations of gene dynamics in our two-sex life history model imply a large "energy surplus" on the part of males. This allows the male form to devote energy to the development of some male traits that help the males to compete for access to females. Eventually, this competition leads to the dimorphism of sex-specific traits. Using this life history model, we are able to explain many features of sexual dimorphism, as well as why males often transfer less to their offspring than do females, and why only females have menopause.