Why sexual fidelity matters more to men

Sexual infidelity in a long-term relationship, such as marriage, is undesirable to both men and women.

Since the major goal of forming a long-term relationship is to have repeated sex in order to increase the odds of conception, if a person looks for sex outside the relationship he’s straight-out rejecting his current partner.

Generally, sexual infidelity is more painful to a man than a woman. While there’s a chance that a woman may forgive a man who fools around, it’s a rarity for a man to condone his unfaithful female partner.

Of course, there are evolutionary reasons behind this behavior and I’ll be throwing some light on those very reasons in this post. Wait, let me get my torch…

When men cheat

Women expect their long-term male partners to invest resources, time and effort and into the relationship, especially into the raising of children. The best indicator of whether a man would do this is his level of commitment. And, for a woman, the best way to test a man’s level of commitment is to figure out how much he loves her. If he’s truly, madly and deeply in love with her then she can be sure that his commitment level touches the sky.

When a woman catches her male partner cheating on her, the first thing she does is check and re-check his commitment levels- that seem to have dropped thanks to the cheating episode. She asks him questions like, “Do you love her?”, “Are you planning to leave me?”, “Do you still love me?” and so on.

These questions are designed to test the commitment level of the man. If he somehow reassures her that his commitment level to their relationship hasn’t dropped at all, there’s a good chance that she’ll forgive him. 

Anything that the man does to re-assure her that he’s still committed to her increases the odds that she’ll forgive his error and move on.   

For example, if the man says things like, “Of course I don’t love her”, “I was drunk and have no idea what I was doing”, “It was a one-time thing”, “I’ve always loved you and you alone” and so on, there’s a good chance that the commitment level of her partner in her eyes will soar again if she believes him. She may warn him not to repeat the behavior in the future though.


It’s important to understand that even though women are more likely than men to forgive their cheating partners, they don’t always forgive them. To what degree a woman will forgive her cheating partner depends on many factors.

Long story short, if a woman has little to lose reproductively from her cheating partner, then she’s more likely to forgive him. Conversely, if she has much to lose reproductively from a cheating partner, she’s less likely to forgive him.

For instance, if a woman is married to a high-status and resourceful man, she may condone his cheating behavior because such a partner is hard to get. As long as he’s investing in raising the kids in the best possible conditions, her reproductive success won’t be threatened. But if she’s very attractive she may have no problem dumping him and finding another high-status man.

If a woman has been with a man for 20-30 years, it’s very likely that her children have already reached puberty and received good care and education. Her reproductive success is more or less ensured in this case. Her children have now reached the age where they can seek their own partners, adding to the replicating success of their mother’s genes.

Therefore, she no longer expects the same level of commitment from the man that she did when they began their relationship. So, if he fools around now, she’s likely to forgive him.

Compare this to a woman who has just entered a relationship or has small kids that need continual care, protection and feeding. She expects the highest levels of commitment from her partner during this stage because her reproductive success is at stake.

If a man cheats on her at this stage, she’s less likely to forgive him, unless, of course, he succeeds in reassuring her that his commitment level hasn’t gone south. If not, she’ll definitely leave him and try to find some other loving and committed mate.


When women cheat

Sexual infidelity by a long-term female partner is more painful for a man simply because he has a lot to lose from it reproductively- a lot more than a woman whose man cheats on her.

When a man chooses a woman as his long-term partner, he’s ready to invest his resources, time and energy into protecting and raising any offspring that he has with her. But before he can do that, he needs to solve one very important evolutionary problem. He needs to be sure that the offspring that he raises are his own.

While a woman can be sure that the children she bears contain 50% of her genes, a man cannot be sure that the offspring that his partner bears contain 50% of his genes. It’s possible that she was impregnated by another male.

If a man ends up investing his resources, time and energy into offspring that are not his own, the reproductive costs are huge. There’s a possibility that his genes will slip away into reproductive oblivion, especially if he devotes all his resources and time into raising genetically unrelated offspring.

Men solve this problem of paternity uncertainty by marrying women i.e. ensuring their own repeated sexual access to women so that the probability of any other male impregnating their women becomes close to zero.

This is precisely why men find it hard to forgive their partners who’re sexually unfaithful to them. Even if they detect the possibility of a future sexual infidelity, they engage in typical ‘guarding’ behaviours such as not allowing their partner to go anywhere on their own, threatening other males who try to come close to their partner, raising suspicion after suspicion, and so on. 

If they do find out that their female partner has been cheating on them, they’re at times enraged to the point of violence and murder.

It’s, therefore, no wonder that men, more often than women, commit crimes of passion borne out of sexual jealousy, be it murdering their partner, the male that she fools around with, or both.

Although both men and women can be victims of domestic violence, women are more often the victims. In many cases, the man perpetrates violence because he holds some kind of suspicion about the fidelity of his partner. 


It’s important to understand that even though men find it hard to forgive sexual infidelity if somehow their losses are mitigated they might be more forgiving than they generally are.


For instance, a polygamous man who invests his resources and time into a number of women has less to lose if one of them turned out to be sexually unfaithful. He could still invest into the offspring that other sexually faithful wives bear and be fairly confident that he’s raising kids carrying his own genes. 

Therefore, there’s a good chance that he may forgive that one woman who turned out to be sexually unfaithful to him.



Lee H. Baucom, Ph.D. teaches how to overcome the issues commonly faced by people in their marriages in his popular online course- Save The Marriage System.
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