Did you pick your mate because “birds of a feather flock together?” or because “opposites attract?”

Researchers have found increasing evidence that the former is often true, even when it comes to genetics. Spouses share more genetic similarity than individuals who are randomly paired, they report today in the journal Proceedings of the National Academy of Sciences.

“It is well established that individuals are more similar to their spouses than other individuals on important traits, such as education level,” the authors wrote. “The genetic similarity, or lack thereof, between spouses is less well understood.”

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The researchers compared 1.7 million single nucleotide polymorphisms (SNPs) within the genomes of 825 non-Hispanic white heterosexual American spousal couples to SNPs of randomly selected, non-coupled pairs of individuals to discover that there is a degree of preference for similar genetics. Still, it’s not close to the degree that education matters in coupling — at most, genetics accounts for 1/3 of the magnetism that education does, they said.

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The research could help social scientists uncover underlying reasons for mating in their work on whether and why people partner based on factors such as height, education, religiosity nd political partisanship, the authors say. And it could also help inform statistical models used in genetic epidemiology.

Further studies would need to be done to expand the pool of participants to include more races, interracial couples, and homesexual couples, the authors note.

Photo: Madchen/PYMCA/Getty Images