structural:expansion
Genetic diversity, relaxed sexual selection and immunity

While upper body strength is on average more sexually dimorphic in humans than in most other primates, with the exception of gorillas, some fossil evidence suggests that male upper-body strength and muscular sexual dimorphism during human evolution peaked in Homo erectus and decreased, along with overall robustness, during the evolution of H. sapiens with its neotenic traits. The reduction in sexual dimorphism would suggest that taxa with high sexual dimorphism do not necessarily have an increased evolutionary advantage. This could be explained by the theory that sexual dimorphism could reduce genetic diversity in a population, i.e., if individuals are attracted to only highly masculine or highly feminine mates, then those without distinctly gendered features are excluded as potential partners, thus creating speciation.