Assortative Mating is a Natural Consequence of Heritable Mate Preferences and Preferred Traits

Assortative mating – the tendency for individuals to pair with partners similar to oneself – is the most ubiquitous and well-established phenomenon in human and animal mate choice. Numerous adaptive and non-adaptive explanations have been proposed, yet a simple explanation has been overlooked: assortative mating is a natural consequence of heritable preferences and preferred traits. When individuals choose partners based on heritable preferences and preferred traits, genetic correlations form between preferences and traits. If individuals’ preferences are correlated with their traits, it follows that individuals would prefer and choose partners whose traits are similar to their own. To demonstrate this mechanism, we developed an agent-based model simulating 100 generations of evolution of traits and preferences through sexual selection with no additional selection pressures. Agents had traits and preferences, each uniquely determined by alleles at 40 loci. Agents chose mates based on how closely potential mates matched their ideal preference values and reproduced with independent assortment of alleles. Genetic correlations quickly formed between traits and corresponding preferences within individuals, and mating pairs came to have similar traits (i.e. assortative mating), even when up to ten preferences were used in mate choice. While our model is an intentionally simplified representation of reality, it revealed that heritability of preferences and preferred traits is sufficient to drive a universal pattern of assortative mating, even in the absence of the more complex dynamics previously proposed.