Sexually reproducing organisms often rely on various traits to judge the attractiveness of potential mates. Many mate choice preferences and traits have evolved through selection by those organisms’ ancestors, with traits having been either costly (detrimental to survival) or noncostly in the environment of their evolutionary adaptation. A general mathematical analysis of the evolution of traits used in mate choice is presented. The analysis builds on a combination of Price's covariance equation and Wright's method of path analysis, and includes a set of Monte Carlo simulations. The usefulness of the mathematical analysis is demonstrated through the development of a small but important set of hypotheses and implications for the human species: (1) costly traits used in mate choice by humans should be generally less common and more attractive to the other sex than non-costly traits; (2) costly traits should be disproportionately less common in human females than in males; and (3) some harmful human mental disorders, such as schizophrenia, may have co-evolved as costs of attractive mental traits. It is also shown that similar analyses can be easily employed by evolutionary psychologists to theorize about the evolution of complex mate choice traits, and to test the resulting theories with modern humans through the method of path analysis.