"Men are more likely to spread their seed” he said, “ This is why we cheat. Women on the other hand, tend to stay at home and ‘nest’. Somebody has to take care of the kids right?”

He leaned back, apparently satisfied with his answer and chuckled at the look on my face.

I guess if one of the sexes decides to cheat, it might as well be men right? This is just a snippet of a conversation that I had with a male friend of mine. He was joking but I know that he didn’t just pull these ideas from the sky. Men have been saying variations of the same thing for decades. Given what he said, I wanted to see if there was any evidence to back up this assumption. As it turns out, this sentiment is only partially true. It’s a misconception that’s only surfaced because of our flawed ideas about relationships. While it may seem that men need to "spread their seed" to encourage the continuation of the species one the surface, research suggests this may not be the whole truth. As it turns out, women also like to play the field.

Read: What Exactly Is an Affair?

Fast forward to a week after researching the source of infidelity. I told him “You aren’t the only ones straying outside your marriage. Women get theirs too. Trust me. It’s only a matter of time before you realize that.”

He leaned forward “Anna, that’s just not how girls act. How do I know this? Look around you, that’s just not how the world works.”

According to the academic journal “Current Opinion in Psychology” in an essay entitled “Infidelity in Romantic Relationships”, “two to four percent of spouses report having sex with a secondary partner ... both males and females are engaging in infidelity at similar rates.” This turns the previous assumption on its head and demonstrates that women are just as likely to stray as men.

Both males and females are engaging in infidelity at similar rates.

There’s also a preponderance of research that shows that women have embraced a variety of different relationships for thousands of years, not just the traditional monogamous relationships found in the West. One such form is polyandry. Polyandry is a type of relationship where one woman may take multiple "co-husbands." These types of relationships are common in forager civilizations and are said to go back to hunter-gatherer societies. According to Dr. Starkweather and Dr. Hames in their academic essay “A Survey of Non-Classical Polyandry”, polyandry is rare, but it’s not nearly as rare as people would think. They had the opportunity to study 53 cultures that practice this form of romantic engagement, and came to a number of conclusions.

According to the study, polyandry might have traditionally been a way in which families consolidated and maintained plots of land among the male's family (the co-husbands were usually brothers who took an outside bride). Over time, these relationships became less of a contract and more romantic. The implication of this essay indicates that women are socially built to take multiple partners. We can further see this in numerous cultures that broaden the definition of what it means to be part of a non-traditional family.

After I told my friend about this research, I paused. He leaned back, clearly thinking about what I’d just said.

“Well that type of relationship seems justified in that there’s a ‘contractual’ reason for their relationship. Also, it can’t be proven that this relationship became ‘romantic’ because men have a tendency to be territorial. A man isn’t going to just sit by and let another man take his woman.”

I pondered this for a second

“The issue with that is that there are numerous cultures where women have sex with multiple men and the men take care of the child.”

The look on his face was priceless. This seemed to give him pause.

There’s no greater example of this than in certain parts of the Amazon, where it’s also not uncommon for women to take multiple lovers. According to Amazonian customs, when a woman bears a child with any of her lovers, all the men involved are considered the biological fathers, whether they actually fathered the child or not. This helps maintain a community culture where each of the men were considered part of the family unit and helped nurture and protect the family. As it stands, if you don’t know who the biological father is, it’s safer to take care of the child just in case it happens to be yours. In this way, the woman’s sexual relationships with multiple men functions as a deterrent and actually encourages both men AND women "nest," taking care of the child as a community.

“Alright, that’s fine. There are always exceptions to the rule. What I’m saying is, across the board this isn’t the case. Men and women cheat at about the same rate, right? Can we at least agree to the fact that women just aren’t set up like that? Like, they aren’t biologically built to take more than one partner.”

He looked at me when I didn’t immediately answer.

“Right?”

As it turns out, women’s tendency to wander (and its consequences) might be rooted in evolution.

Read: The 4 Things I've Learned Since I Started Swinging

In their book “Female Infidelity and Paternal Uncertainty”, Steven Platek and Todd K. Shackelford talk about "sperm wars" in men and women and how women might be hardwired to seek out multiple partners in prehistory. They researched multiple instances of insemination in ancestral women. They state:

“Facultative polyandry (female sexual infidelity) would have been the most common reason for the simultaneous presence of live sperm from two or more men in the reproductive tract of an ancestral woman.”

In other words, we’ve been doing this for a long time, to the point where men became threatened because of our promiscuity. This might have helped create the social structure of monogamy. They suggest the reason for modern man's persecution of women who cheat/seek out multiple sexual partners might be rooted in something called "sexual jealousy."

Sexual jealousy is a mechanism that maintains monogamy. For men, that means that their sperm "wins" the sperm war due to lack of competition. This effectively makes it so that their genes stay in the gene pool, making it more than likely that his genes will fertilize the woman without having to compete with other men whose sperm would otherwise be present in her reproductive tract.

Read: 8 Ways Polyamory Helped Shape My Monogamous Relationship

However, Platek and Shakleford make an interesting point: sexual jealousy wouldn’t have developed unless women didn’t practice monogamy to begin with.

The research implies that it’s a completely natural, ancestral tendency of women to seek partners outside of their monogamous pairing. However, this urge is suppressed by society - just barely - and they cheat just as much as men. It could be argued that woman’s polygamous instinct caused society to evolve toward monogamy, especially for women whose sexual liberation threatened male genetic continuance. Women who go against the grain are punished or looked down upon, while women who stay at home are rewarded.

In short, while the West holds certain ideas about men’s propensity to engage in infidelity and women’s tendency to "stay at home and nest," recent research is beginning to turn this misconception on its head. Instead, we’re beginning to find evidence that not only shows that men and women cheat in equal measure, but that there are also evolutionary reasons why women may engage in relationships with multiple men outside of their monogamous relationships.

All in all, I think this sheds light on the breadth and depth of cheating in relationships. If we know the why and how of cheating maybe we can explore other options in our relationships or at least be more forgiving. I think my friend and I left that conversation with new ideas about how relationships work.