Humans are hardwired to fall out of love and move onto new romantic relationships, according to a new study.
The study also found that a man is more likely to end a relationship because a woman has had a sexual relationship with another man.
On the other hand, a woman may be more likely to break up if her partner has been emotionally unfaithful.
"Our review of the literature suggests we have a mechanism in our brains designed by natural selection to pull us through a very tumultuous time in our lives," said Brian Boutwell, associate professor of criminology and criminal justice and associate professor of epidemiology at Saint Louis University.
Boutwell and his colleagues examined the process of falling out of love and breaking up, which they call primary mate ejection, and moving on to develop a new romantic relationship, which they call secondary mate ejection.
They found men and women might break up for different reasons.
For instance, a man is more likely to end a relationship because a woman has had a sexual relationship with another man. For evolutionary reasons, men should be wired to try and avoid raising children that are not genetically their own, the researchers said.
On the other hand, a woman may be more likely to break up if her partner has been emotionally unfaithful partly because of evolutionary reasons.
Over the deep time of evolution, natural selection has designed mate ejection in females to avoid the loss of resources, such as help in raising a child and physical protection, that their mates provide.
Brain imaging studies of men and women who claimed to be deeply in love also provided important clues about dealing with breakups, researchers said.
Functional MRIs showed an increase in neuronal activity in the parts of the brain - the pleasure areas - that also become active with cocaine use, researchers said.
Falling out of love, Boutwell said, might be compared to asking a cocaine addict to break his or her habit.
Building off the drug addiction analogy, Boutwell examined studies about the brains of former cocaine addicts to try to predict how the brains of those who are breaking a relationship habit might look.
Images of the brains of those no longer using cocaine showed a larger volume of gray matter in various brain regions.
"We might argue that different regions of the brain act in a way that once that addiction has been severed, then help to facilitate a person moving on and finding a new partner," Boutwell said.
"A person might initially pursue their old mate - in an attempt to win back their affection. However, if pursuit is indeed fruitless, then the brains of individuals may act to correct certain emotions and behaviours, paving the way for people to become attracted to new mates and form new relationships," he said.