Multivariate mate choice constrains mate preference evolution

Mate preferences are ideals or standards believed to guide mate choice, which is crucial to an individual's inclusive fitness. In evolutionary psychology, many mate preferences are theorised to have evolved because choosing a partner with the preferred trait offers inclusive fitness benefits. This evolutionary logic assumes that individuals mate with partners whose traits align with their preferences. However, studies often fail to find an association between preferences and actual mate choices. Recent theoretical work suggests that the more preferences used to evaluate potential partners, the weaker this association becomes. These findings raise questions about the conventional view that the large number of observed human mate preferences have evolved independently and simultaneously. Here, we built a computational agent-based model that simulates the evolution of ten traits via natural selection and the resulting evolution of up to ten preferences via sexual selection, varying the number of preferences from one to ten. We developed one model in which preferences evolved through indirect selection and another that added direct selection. Initially, in models with fewer preferences influencing mate choice, preferences evolved visibly alongside preferred traits. However, the more preferences that influenced mate choice, the slower the rate of evolution of preferences. Under the ten-preference model, preferences showed minimal evolution under indirect selection, whereas the addition of direct selection led to more substantial changes, indicating greater robustness to these constraints. Given the numerous mate preferences observed in humans, our findings suggest that we may need to refine some explanations of how these preferences evolved.