The Biology of Infidelity

infidelityIt seems like a cop out, doesn’t it? “I’m sorry honey – I wanted to be faithful, but the human mind is programmed to reject monogamy.” Try that line and get ready to duck the frying pan and the divorce papers.

On the one hand, humans are a “pair bonding” species that appears to gravitate toward having one partner at a time. On the other hand, humans are one of the only mammals that do that. There actually is some evidence to support the idea that monogamy is not the most natural state of human existence. There are both biological and psychological reasons why people aren’t necessarily at their best when they are with one person for their entire life.

Is the Human Mind Programmed to Reject Monogamy?

According to, there are a few biological indicators that seem to point toward humans being more inclined toward polygamy. First off, there are studies that indicate that women are more likely to get pregnant from an affair than from their spouse, even if they have more sex with the spouse. The genetic advantage to this would be that a woman could create a wider genetic range of offspring, which in turn increases the chance that one of them will survive.

Another interesting study shows that men actually produce more sperm when they are not in the presence of their wives. This, again, would seem to be a biological adaptation to help create a better genetic variance by allowing a man to impregnate as many women as possible. Or it could be a genetic adaptation to lead to a really steamy reunion when he gets home.

What are the psychological reasons why humans might resist monogamy?

Sex basically comes down to an attempt to pass your genes on to another generation, and sexual behavior is designed to increase your chances of doing that. Having sex more times, with more partners of various genetic makeups, is a great way to assure that your genes will be passed on, and somewhere deep down, we all realize that.

For men, it may even go deeper than that. Men, for whatever reason, have an almost constant need to prove that they’re men. This can lead to lifting things that are far too heavy, getting ill-advised tattoos, and sleeping with people they really shouldn’t. Sexual prowess has always been equated with masculinity for men, and nothing says sexual prowess like having a string of lovers on the side. Of course, the masculinity suffers a bit when you lose everything you own in divorce court, but up until that moment, a man can feel quite masculine.

For women, the psychological component of cheating is actually more of an emotional one. Women, as a rule, have complex emotional needs that do not really diminish much over time, while for most men, the desire to fulfill complex emotional needs tends to diminish sharply over time. This need will often drive women to have affairs, both emotional and physical, as their primary relationship ages.

Are humans mostly monogamous in practice?

If you watch television and believe what you see, the answer is a resounding no—humans are not mostly monogamous. In fact, it seems like most people will pretty much have sex with anything that isn’t moving fast enough to get away or on fire. This is an exaggeration that the media has created, but it comes from a glimmer of truth—a fairly large number of people do fool around. tells of a 2006 survey that showed that 28% of men and 15% of women 60 years old or older admitted to having had an affair at some point in their lives. There are likely many more who had affairs and didn’t admit to it. There are also people who recognized that monogamy was not for them and either chose not to have a monogamous relationship at all or left it earlier in their lives.

What other options are there besides monogamy?

If you don’t want to be in a monogamous relationship, don’t worry, you can always hop from bed to bed throughout your younger years until you finally get to die bitter and alone in a house filled with cats. Okay, there are some other options, too. If your religion supports it or if little things like the law don’t bother you, there’s always polygamy.

If you’re not ready to commit to having multiple spouses, there is always the open relationship. While “opening up the relationship” has traditionally been a final step before divorce, these days more and more people are having successful open relationships that last as long, or longer, than monogamous relationships.

Since the dawn of time, human beings have held monogamy to be the natural state of being, but it’s quite possible that this is a mistake. There are a number of indicators that say that we might actually be wired to have multiple partners. Of course, maybe our ability to overcome our biology is exactly what separates us from the other animals, assuming we can actually do it.