If you’ve ever noticed that some married couples look alike, you’re not being creepy or wrong. This is a real thing, and there are good reasons for it.
And no, this isn’t the same as people looking like their dogs.
According to a new study published April 6 in PLOS Genetics, there’s a simple reason for this phenomenon, and it’s not as surprising as you might think.
Up until very recently, most people found their spouse in their local community — most likely at high school, church, or local events — and that person had the same basic ancestry. Many generations of this creates a genetic structure in the population, which means that marrying someone who looks like you has less to do with preference and more to do with shared ancestry.
However, while picking someone of similar ancestry was the norm for older generations, due to the increase of mobility in younger Americans (who will move 11.5 times in their lifetime), fewer people are marrying or partnering with someone from their hometown.
The researchers in the study explored genetic similarity between spouses from three generations of white people in the Framingham Heart Study, an ongoing examination of heart health in the residents of Framingham, Mass., which began in 1948. The researchers used geonomic (the study of genes) data to define the ancestry of more than 800 pairs of spouses and observed that individuals of Northern European, Southern European, and Ashkenazi ancestry preferentially chose spouses of the same background. But they noted that each successive generation was less likely to choose a spouse with the same ancestry.
The findings from this study reflect demographic patterns and how they have changed during the past 60 years in Framingham and, theoretically, throughout the United States.