The Real Reason Some Couples Look Alike

You know that uncanny resemblance that so many married couples seem to have to each other? Well, there's proof that the observation isn't just all in your head. People really do tend to seek out mates that look like them.

The reason for this may lie in the long-held human tendency to marry someone with the same ancestral background. A study published in 2017 in PLOS Genetics examined the ancestry of 879 participating spouses by studying their genomic data, and found that Northern and Southern Europeans, as well as Ashkenazi persons, chose mates with a similar ancestral background more often than others (via Reader's Digest). The study authors, researchers Ronnie Sebro of the University of Pennsylvania, along with Josée Dupuis from the Boston University School of Public Health and Neil Risch from the University of California, San Francisco, explain why this might be. "Until recently, most people selected a spouse from within their local community, and that person often had the same ancestry."

This pattern seems to be changing though. Whether because of the trend to marry at a later age than in previous generations, or because communities have grown due to ease of travel for work and school, or even because of online dating, the researchers found that the genetic similarities between couples have decreased with each successive generation since 1948, when the study started (via ScienceDaily).

There seem to be other reasons for the look-alike phenomenon, too. Apparently, we prefer ourselves and what is familiar to us over the unfamiliar, even when it comes to love. In a 2013 experiment, researchers showed individuals pictures of their romantic partner's face, which had been altered to include features of either the study participant's own face, or the face of a stranger. Both male and female participants consistently preferred the composite that included their own face, to the others (via TIME). Other studies have also shown that people tend to be more attracted to individuals who resemble their opposite-sex parent.

Even for those couples who don't necessarily look much alike at first, that will likely change as the years go by. Shared lifestyle patterns, as well as many shared experiences, lead to physical similarities that scientists describe as "convergence of appearance." The couple's history together gets literally etched into their faces in the same laugh lines and expressions. And, according to Bright Side, the happier the relationship, the more similar a couple will end up looking.