Introduction. Genital morphology (especially male) among the animal kingdom is characterized by extensive differences that even members of closely related species with similar general morphology may have remarkably diverse genitalia.
Aim. To present the sexual medicine specialist with a basic understanding of the current hypotheses on genital evolution with an emphasis on the sexual selection theories.
Methods. A review of current literature on the theories of genital evolution.
Main Outcome Measures. Analysis of the supporting evidence for the sexual selection theories of genital evolution.
Results. Several theories have been proposed to explain genital evolution. Currently, the sexual selection theories are being considered to present valid and solid evidence explaining genital evolution. However, other theories, including sexual conflict, are still being investigated. All theories of genital evolution have their own weaknesses and strengths.
Conclusions. Given that many complex biological mechanisms, mostly unknown yet, are involved in the process of genital evolution, it is thus reasonable to conclude that not one theory can independently explain genital evolution. It is likely that these mechanisms may prove to have synergistic rather than exclusive effects. Shamloul R, El-Sakka A, and Bella AJ. Sexual selection and genital evolution: An overview. J Sex Med 2010;7:1734–1740.