Singletons, next time you want to pick up a stranger at the bar, rather than asking for their number, you should ask “what’s your genotype?” Although you may get blank stares, and possibly rejected this will actually increase the likelihood of finding your perfect match to marry. According to a recent study published in the journal Proceedings of the National Academy of Sciences, married couples tend to be more genetically similar to their spouses than they are to randomly selected individuals from the same population.
“It’s well known that people marry folks who are like them,” said Benjamin Domingue, lead author of the paper, and a research associate at CU-Boulder’s Institute of Behavioral Science, in the CU-Boulder news release. “But there’s been a question about whether we mate at random with respect to genetics.” People do tend to marry others who have similar characteristics, including religion, age, race, income, body type, and education, among others, but Domingue and his colleagues wonder whether couples share similarities in their DNA.
In an effort to understand the social and biological mechanisms that leads to similar couples getting married, the team of social and behavior scientists at CU-Boulder compared the statistical likelihood people would marry those of genetic similarity to those who have similar educations. Domingue and his colleagues drew data from a large ongoing Health and Retire Study, sponsored by the National Institute on Aging. A total of 825 opposite-sex, non-Hispanic white married couples, with more than half born during the 1930s, were observed in the study. The scientists specifically looked at the single-nucleotide polymorphisms — places in people’s DNA which are known to commonly differ among humans.
The findings revealed mating isn’t truly genetically random, as these married couples were more genetically similar than randomly pairs of people within the same population. However, after controlling for educational attainment, the genetic effect declined by 42 percent. When it came to educational similarity between spouses –— known as the assortative effect on education — it was found to be three times stronger than sorting based on genes.
This study does not undermine the role genes play in traits such as intelligence, geographical origin, among others, but suggests genetic similarity is subconsciously taken into account when choosing a mate. The researchers do acknowledge this study has several limitations because it only focused on opposite-sex, non-Hispanic white couples within the U.S., encouraging further research, the Los Angeles Times reported. "The results represented here only represent a first step in understanding the ways in which humans may assortively mate with respect to their genome," the study authors wrote.
In a similar 2010 study published in the journal Personality and Individual Differences, a team of researchers at Michigan State University found married couples do not become more similar over time, but rather they tend to pick their spouse based on shared personality traits. This similarity was originally thought to be because of spouses’ influence on each other over time, but this study supports the belief that these shared traits are what drew them to each other in the first place. Therefore, spousal similarity is better explained by selection than gradual influence.
People tend to pick spouses who have similar backgrounds and characteristics, including race, religion, age, income, and body type. Now, researchers believe genetic similarity can now be added to that list. Perhaps you should try the pick-up line: “I like your genes.”
Boardman JD, Conley D, Domingue BW, Fletcher J. Genetic and educational assortative mating among US adults. PNAS. 2014.
Burt SA, Donnellan MB, Humbad MN, Iacono WG. Is Spousal Similarity for Personality A Matter of Convergence or Selection? Personality and Individual Differences. 2010.