What attracts you to a partner? Nice eyes? A good sense of humor? According to a new study by researchers from the University of Colorado Boulder, most of us are likely to choose a partner who has similar DNA to our own.

The research team, led by Benjamin Domingue, a research associate of the Institute of Behavioral Science at the university, notes that past research has already determined that people tend to be attracted to others who have similar characteristics, including similar income, race, age and body type.

But in this new study, recently published in the Proceedings of the National Academy of Sciences (PNAS), the team assessed similarities between partners across the entire genome – something they say has never been done before.

“It’s well known that people marry folks who are like them. But there’s been a question about whether we mate at random with respect to genetics,” says Domingue.

To try and answer this question, the team analyzed the genomes of 825 non-Hispanic American married couples who were a part of the University of Michigan Health and Retirement Study – a longitudinal study that surveys over 26,000 people aged 50 and over every 2 years.

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Researchers found that married couples had fewer differences in their DNA, compared with non-coupled pairs.

During their analysis, they focused exclusively on couples’ single-nucleotide polymorphisms (SNPs). These are areas of DNA that commonly differ among each individual. They compared 1.7 million SNPs among married couples with that of non-coupled pairs in the general population.

The researchers found that, overall, married couples had fewer differences in their DNA, compared with non-coupled pairs.

They then compared the degree of genetic similarity between married couples with that of married couples with similar education – a widely studied theory referred to as “educational assortative mating.”

But the team found that preference for a partner with similar DNA – which the researchers refer to as “genetic assortative mating” – is approximately a third of the strength of educational assortative mating.

Commenting on the study results, the researchers say:

We provide evidence for genetic assortative mating in this population but the strength of this association is substantially smaller than the strength of educational assortative mating in the same sample. Furthermore, genetic similarity explains at most 10% of the assortative mating by education levels.”

However, the teams notes their findings could be of significance to scientists who use statistical models to determine differences between human populations, since these models tend to assume that people choose partners at random.

In addition, the researchers say their findings pave the way for future research looking at whether married people of other races have genetic similarities, or whether people choose friends that are genetically similar.

In 2013, Medical News Today reported on a study suggesting that women are attracted to low-voiced men who cheat, while other research suggests that we do not need to see a partner’s face to know how they are feeling.

Written by Honor Whiteman