Illustration by Erin Taj

My Dad Cheated on My Mom. Does That Mean I’m Going to Be A Cheater, Too?

Is infidelity in my DNA?

The timing was almost unbelievable. About 18 months ago, I found out my dad had been cheating on my mom. About six months later, my husband found out that his mom had been cheating on his dad.

How my husband and I each found out was indicative of just how different our parents are. Mine were dealing with this for months before I knew for certain. In fact, they didn’t even tell me. My twin sister did. Their reasoning was that they didn’t want to add any stress to my plate because in their minds, I was in a vulnerable (read: pregnant) state. As much as I appreciated their concern, like I said, it wasn’t exactly a shocker.

My parents — who married later in life — generally seemed to care for each other (and still do). But over the course of their nearly 30 years together, I never thought of them as particularly “in love.” Their love for me and my siblings was never in question, and I’m grateful for that. But as far as a model for a romantic relationship goes — not so much.

My husband’s parents, on the other hand, met when they were 18 and 19 years old, got married six months later and had two kids by the time they were 25. To say his family is passionate would be an understatement. Whereas my family was stable in nearly every way, his had dramatic ups and downs — financially, emotionally, mentally … you name it. But they at least talked (and talked and talked) about their problems out in the open, which was the complete opposite of my upbringing, where most issues were rarely discussed. And so, unsurprisingly, my husband and I found out his mom had cheated on his dad the same day my father-in-law did. We then proceeded to learn more details about the situation than we ever cared to know.

Yet, with all these differences, both relationships ended in the same way.

The fact that these revelations bookended the somewhat tumultuous months surrounding the birth of our son made the impact that much greater. Having just become a parent myself, the general fear of turning into your own parents that inevitably comes with age — more pointedly, the fear of repeating their mistakes — got an added layer I wasn’t necessarily prepared for. Would my husband eventually cheat on me? Would I eventually cheat on him? It had never seriously crossed my mind before. but now, with these two not-so-shining examples of our possible future selves, I started to think about it more closely.

Of course, the easy answer is that people cheat because they aren’t getting what they want or need — physically or emotionally. But I began to wonder if there was something else to it as well. Something more tangible, more biological. Especially after I witnessed the incredible mix of physical attributes my husband and I both passed on to our newborn son. After all, there is one thing we absolutely share with our parents — our genes. So I wanted to see if there was something in my husband or my genes that might make us more likely to cheat on each other.

As with all things genetic, the answer is complicated. “It’s about half and half — genetics and environment,” explains Brendan P. Zietsch, a psychologist at the University of Queensland in Australia. “But there’s not one definitive infidelity gene. Instead, there are probably hundreds or thousands of genes whose effects combine to make a person more or less likely to be unfaithful.”

Two years ago, Zietsch and his team of researchers conducted one of the most extensive studies ever on the possible genetic component of infidelity. Specifically, they analyzed the genes of 7,378 Finnish adults aged 18–49, a sample comprising of mostly non-identical twins and their siblings, all of whom had been in a monogamous relationship for at least a year. Out of this sample, 9.8 percent of men and 6.4 percent of women reported having had one or more sexual partners besides their partner during that year.

Since this was a twin study, Zietsch was able to analyze how broad-sense genetic differences related to cheating. He found that about 63 percent of the men and 40 percent of women who cheated showed different genetic influences than their siblings who didn’t cheat. (This is essentially the science behind the half-and-half he mentions.)

Zietsch also specifically checked for a link between cheating and mutations of certain vasopressin and oxytocin receptor genes. “Vasopressin and oxytocin are hormones involved in many physical and social functions, including bonding between mother and child and between partners,” Zietsch says. What they found was that oxytocin receptors didn’t have any correlation with cheating, but five different variants of the vasopressin gene did seem to show up in a significant number of women who were unfaithful. (It’s generally thought that men cheat more, but a 2011 report from the Kinsey Institute at Indiana University found that modern men and women are cheating at about the same rate — 23 percent for men and 19 percent for women — though, again, a true average of such illicit activity is notoriously tough to pin down.)

Interestingly, a separate 2008 study also investigated the same vasopressin receptor and found that one specific version of that gene directly influences how men view the quality of their relationship. That study didn’t look at infidelity, but it did link the hormone with the degree of marital strife men (and, by extension, their partners) experience.

In addition to vasopressin, the impulse to cheat also could have something to do with a dopamine receptor gene called DRD4, which is essentially a pleasure-seeking gene that some research has linked to an inclination toward risky behaviors such as gambling and substance abuse (though the results have been conflicting).

For example, a 2010 study led by Justin Garcia, a doctoral diversity fellow at Binghamton University, indicated that individuals with a certain variant of the DRD4 gene were more likely to have a history of uncommitted sex, including cheating on their partners. According to Garcia, “The motivation seems to stem from a system of pleasure and reward, which is where the release of dopamine comes in. In cases of uncommitted sex, the risks are high, the rewards substantial and the motivation variable — all elements that ensure a dopamine ‘rush.’”

Both of Zietsch’s and Garcia’s studies, however, only found correlations, not causal relationships. When I ask if having one of the vasopressin receptor variants meant that a person was doomed to cheat, Zietsch tells me, “Definitely not. It might make you very slightly more likely to cheat, but even that’s uncertain.”

The fact that it was my father and my husband’s mother — our supposed models for the people we would eventually choose to spend the rest of our lives with — who cheated is not lost on me. Did we each subconsciously choose someone with the potential for future infidelity? I would reason that the timing of our parent’s affairs somewhat discounts that idea, since adultery wasn’t something we were exposed to growing up, or even before we had married. It also made it, at least in my case, a little easier to stomach. So that takes care of the environment part.

As for genetics, I’m more convinced than ever that they’re as much of a crapshoot as the environmental twists and turns the rest of our life together could bring — e.g., financial strife, tragedy and/or parents who divorce at the very moment they’re supposed to kick back and enjoy each other’s company for however long they have left on this mortal plane. (Or, to look at things a little more positively, the riches, successes and happiness the next half-century could be filled with.)

In other words, I’ve resigned myself to the fact that I can’t pretend to know the future. Nor am I afraid that either my husband or I will cheat. Though our marriage is far from perfect, I have complete faith in our commitment. If I’m being honest, the thought of our relationship venturing into the resentful, conflict-ridden realities our parents endured is way more terrifying than any rogue infidelity genes that may or may not be lurking in my DNA.

And while it makes me incredibly sad to say it, at least we now have the (unfortunate) benefit of learning from our parents’ mistakes. More than anything else, this experience has reinforced the importance of being honest with each other, even if it’s uncomfortable (especially when it’s uncomfortable), and not expecting the other person to magically become someone different than exactly who they are.