Like Likes Like: Partner Preferences May be Explained by Genetics

Newswise — It is no secret that people are often drawn to romantic partners who seem similar to themselves. This tendency, called assortative mating, has been established in humans (Horwitz et al., 2023; Luo, 2017) as well as other species. Fish, for example, demonstrate the behavior frequently (Jiang et al., 2013).  

Assortative mating has also recently been in focus on social media with the viral Siblings or Dating game, where people guess whether two individuals who look alike are related or a couple. 

The idea is well-founded in academic research. Humans have been observed to select partners with similar physical, personality, and demographic traits (Horwitz et al., 2023), which can impact the genetics of populations—creating subgroups that emphasize the presence of shared traits (Abdellaoui et al., 2015).  

But selecting a partner like ourselves may not be solely determined by personal choice. A new study soon to be published in Psychological Science suggests that assortative mating can be explained relatively simply by looking at the inheritance of preferred traits and corresponding preferences for those traits. 

Coauthors Kaitlyn Harper and Brendan Zietsch from the University of Queensland describe this scenario simply: If you are tall, you may have inherited tallness from one parent (say, your mother) and the preference for tallness in a romantic partner from your other parent (in this case, your father). The combination of those inherited traits means that you exist in the world as a tall person and are attracted to tall people.  

The idea that preference for a particular trait could lead to genetic correlations has been discussed in previous research but is a newer concept for evolutionary psychology, especially in the context of assortative mating.  

“The pieces were there, but they hadn’t been connected in this way before,” Harper said. “Agent-based modeling helped us connect the dots—by simulating populations, we could see that assortative mating naturally emerged without the need for additional assumptions or processes.” 

She added that this research wouldn’t have been possible without an interdisciplinary mindset. 

“The mechanism itself is familiar in evolutionary biology, but it wasn’t thought of as an explanation for assortative mating,” she said. “Making that connection only became possible when we looked across the two disciplines.” 

Listen to this related podcast: Couples Who Laugh Together, Stay Together

To test this theory, the authors ran an agent-based model where partners are chosen according to heritable traits and preferences over 100 generations. They included models with and without selection pressure on the number of offspring within each generation to assess how the theory stands up under more naturalistic conditions.  

They found that even with up to 10 preferences for traits in a partner, clear genetic correlations formed between traits and preferences for those traits, which resulted in the agents choosing partners similar to themselves. Models with selection pressure generated less-stable correlations, which the authors attribute to reduced variance in traits.  

“The power of this finding is in its parsimony—it shows that a phenomenon which has puzzled researchers for decades can be understood through an explanation that was hiding in plain sight,” Harper said. “And because the mechanism is so general, it can also apply to assortative mating in animals, where many of the explanations proposed for humans wouldn’t make sense.” 

References

Abdellaoui, A., Hottenga, J.-J., Willemsen, G., Bartels, M., van Beijsterveldt, T., Ehli, E. A., Davies, G. E., Brooks, A., Sullivan, P. F., Penninx, B. W. J. H., de Geus, E. J., & Boomsma, D. I. (2015). Educational attainment influences levels of homozygosity through migration and assortative mating. PLoS ONE, 10(3), Article e0118935. 

Harper, K.T. & Zietsch, B.P. (in press). Assortative mating is a natural consequence of heritable variation in preferences and preferred traits. Psychological Science, 0(0), 0–0.  

Horwitz, T. B., Balbona, J. V., Paulich, K. N., & Keller, M. C. (2023). Evidence of correlations between human partners based on systematic reviews and meta-analyses of 22 traits and UK Biobank analysis of 133 traits. Nature Human Behaviour, 7(9), 1568–1583.  

Jiang, Y., Bolnick, D. I., & Kirkpatrick, M. (2013). Assortative mating in animals. The American Naturalist, 181(6), 125–138.  

Luo, S. (2017). Assortative mating and couple similarity: Patterns, mechanisms, and consequences. Social and Personality Psychology Compass, 11(8), Article e12337.