You may have more in common with your spouse than you think—like DNA, a new study suggests. Scientists came to their conclusion, published yesterday in the journal PNAS, after reviewing data on 9,429 non-Hispanic whites, a group that included 825 wedded couples. The bigger number of the study: 1.7 million. That's how many single nucleotide polymorphisms—which the Los Angeles Times describes as "the point at which a sequence of DNA differs between individuals"—the researchers reviewed. They observed that spouses often share other traits, like education level, and set out to "estimate the genome-wide genetic similarity of spouses and compare the magnitude" of it to that educational similarity, they write.
Their conclusion: married couples were indeed more genetically similar than two randomly chosen individuals, but that similarity wasn't as pronounced as the educational one: it's no more than one-third the magnitude of educational similarity, they found. LiveScience points out that genes have a hand in a number of traits that may come into play in coupling, like geographical origin and intelligence. It notes that the researchers did control for geography, and their genetic conclusion still held. But the researchers call their results "only a first step" and note other limits, specifically the opposite-sex, white makeup of the couples they reviewed. (More marriage research touches on another similarity, involving booze.)