The Epistatic Handicap Principle Does Work

Unlike the conditional and revealing handicap mechanisms, the epistatic orx “Zahavian” handicap mechanism of sexual selection has hitherto found scant support in the theoretical literature, as it appeared to function only under the most extreme conditions. Here, a continuous game theory model, a quantitative genetics model, and a three locus major gene model are presented which show that the epistatic handicap mechanism can function, independent of the Fisher process, under reasonable assumptions. Moreover, the game theory model illuminates the connection between the strategic and epistatic handicap mechanisms, and illustrates how sexual selection can cause traits to be canalised. The quantitative genetics and major gene models, together with a fourth model, are used to show that a general argument concerning indirect genetic correlations, which has appeared in a number of papers on sexual selection, is specious. The major gene model also illuminates an important distinction between two definitions of mutation bias.