Source
They placed electrodes on the bodies of men and women to measure their physiological reactions to two basic scenarios - imagining their spouses (or loved ones) having (1) sex or (2) engaging in romantic relationships with people of the opposite sex.
Men showed signs of distress and anger such as high heart rate and sweating in the case of sex, and low sensitivity in the platonic relationship scenario, and the opposite was true for women: they showed extreme sadness and anger towards having a romantic relationship with other women compared to sexual infidelity.
According to evolutionary psychologists, male sexual jealousy is driven by men's (unconscious) desire to ensure the spread of their genes, so the idea that someone else may fertilize your woman and then end up raising a child who does not carry your genes is something that explodes a volcano of anger inside you may drive you Sometimes to murder.
They also see that women rely heavily on the man's continuity in providing care for her and her children, and that this is the most important thing to preserve her genes because her egg cells are not compensable and her pregnancy is expensive and needs care.
Therefore, she considers that the emotional relationship is more threatening because it is characterized by long-term and mutual care, which may deprive wives of effort, money and time that is originally the right of their children.
This may explain why many wives tolerate the whims of their men, but they get the most angry in the event of his marriage to another woman or the existence of a long-term relationship with another woman.
It is an evolutionary inheritance, gentlemen, so there is no one who says the argument is that a mistress is the most expensive material and physical cost.