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Saying 'I Do' Because of Similar DNA?

Married couples tend to have genetic traits in common, study states

WebMD News from HealthDay

By Dennis Thompson

HealthDay Reporter

MONDAY, May 19, 2014 (HealthDay News) -- Married couples typically have a lot in common, and researchers now say that may extend to their genes.

Spouses tend to be more genetically similar than two people chosen off the street at random, according to a new study.

It's likely this is because people who are genetically similar have more opportunities to meet and mate -- in other words, "birds of a feather flock together," said lead author Benjamin Domingue, a research associate at the University of Colorado-Boulder's Institute of Behavioral Science.

"Genes drive so many things that can structure opportunities and outcomes that determine who we mate," Domingue said. For example, genes may determine whether your potential partner shares your height or weight, or your ethnic background, religion or level of education.

Domingue and his colleagues examined the genetics of 825 white heterosexual American married couples, comparing 1.7 million potential points of genetic similarity.

The results, published May 19 in the Proceedings of the National Academy of Sciences, found that spouses share a significant number of genetic similarities, compared to any two random individuals.

This conclusion could end up changing the statistical models scientists use to understand genetic differences between human populations, because such models often assume random mating, the researchers said.

The similarity between married folks is not nearly as deep as that between siblings, though.

"Siblings share on average about half their genes, and even within siblings there is variation on that between 40 percent to 60 percent," Domingue said. "The ranges we're looking at between a married couple are much, much smaller, but you do see that spouses share similarities."

The tendency to marry someone genetically similar also is slimmer than the tendency to marry someone with a similar level of education. Genetic similarity between spouses carries about one-third the strength of educational similarity, the researchers report.

Married couples likely have similar genetic traits because their genes helped determine whom they would meet during their lives, Domingue said.

"People with more similar genes end up having similar education, which places them in the same social situations and gives them a better chance to mate," he said.

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