Most people would agree that cheating on a romantic partner is wrong and harmful. Yet it still happens pretty often – and hurts like hell when it does. Why is it so hard for some people to remain faithful to their partners?
Sexperts who study cheating have come up with three theories that might help explain why people do it. In a video put together for the series Love, Factually, evolutionary biologist Dr. David Barash and anthropologist Dr. Helen Fisher discuss the science behind cheating.
Humans aren't naturally monogamous
Biologically speaking, monogamy might not be natural for us humans, explains Dr. Barash, co-author of the book The Myth of Monogamy: Fidelity and Infidelity in Animals and People. Humans are not alone in this, he says, almost all mammals out there aren't 100 per cent monogamous.
But just because monogamy isn't natural for humans, it doesn't mean we can't learn to do it, Dr. Barash emphasizes. Hey, playing the violin isn’t natural for anyone, he points out, but you can learn with practice and it’s great if you can do it! Fidelity is something that takes effort, he argues.
So if it's not natural for humans to have one sexual partner, what are the reasons for them to have several? For men, it's pretty simple. According to the theory of evolution, the more women they have sex with the greater the chance they'll pass on their genes.
Women, on the other hand, wouldn't exactly benefit from getting pregnant every time they cheated on their partner. Even if it were possible, it wouldn’t be desirable: a whole lot of energy and resources goes into pregnancy and raising kids. But a woman could obtain support from the man she’s got on the side if her current partner were no longer in the picture, for whatever reason, says Dr. Fisher. Her lover could be there as a sort of back-up to help her out and provide for her kids if needed.
Cheating is in our genes
But if monogamy isn't natural for anyone, why do some people seem to be better at it than others? Well, one explanation is that it's in their DNA, Love, Factually's host explains. Researchers who study cheating have found two genes linked to infidelity.
The first, DRD4, has to do with the hormone dopamine, which is involved in pleasurable things like having an orgasm. The DRD4 gene comes in different sizes and one study found that people with longer versions were more likely to be into non-committed sex, whether that meant cheating on their partners or having one-night stands.
The other gene is called AVPR1A and could help explain why some women struggle with monogamy. The gene codes for the hormone arginine vasopressin, which is connected to feeling empathy and bonding with a sexual partner. Women with one version of this gene may be more likely to cheat, research has shown.
Our brain systems make us do it
Another theory on cheating has to do with the separate systems in our brain that are involved in romantic relationships and sex. Humans have evolved one brain system that's related to their sex drive, another that has to do with feeling romantic love, and a final system linked to attachment to a partner, explains Dr. Fisher.
This becomes problematic when the three different brain systems are not directed towards the same person, she says. So someone could be sexually attracted to the guy who serves them a cup of coffee every morning and at the same time feel a sense of deep attachment towards the long-term partner they sleep next to every night.