We are taught that monogamy is natural and morally correct and that cheating or having multiple partners is wrong. Some people, including experts in psychology and evolutionary science, argue that monogamy isn’t natural, that it is a learned behavior. Are we pair-bonders? Or are we designed to stray? Among all mammal species, fewer than 10 percent form lifelong partner attachments. It may just be that straying from a partner is in our human DNA. Or is it?
The Evolutionary Argument Against Monogamy
In some ways it seems like bonding with one partner for life would be an advantage. A strong bond between two partners would make for a good environment for raising offspring. Being able to trust each other and caring about each other provides stability and security. On the other hand, by sleeping around, a male animal is able to father more offspring. In the game of natural selection, producing more offspring is generally the goal. For female animals, having multiple partners would provide her offspring with greater genetic diversity. This too could be an evolutionary advantage.
Why Are We Monogamous?
The arguments for multiple partners seem to outweigh monogamy. So why do we do it? Isn’t it more natural not to be monogamous? Researchers have studied monkeys and apes to find the answer. The rate of monogamy is higher in primate species than in mammals generally. A few reasons why we may have evolved to stick with one partner have come to light.
In certain bird species, a male will mate with his primary female and devote most of his time and attention to her and their offspring. But, he will also take time to go out and mate with other female birds nearby. He doesn’t help them raise the baby birds, but he does give them the benefit of his genes. Primates live in more spread-out areas. It may be that traveling from one female to another is not reasonable. For the bird, it’s easy and fast. For a monkey, it is a waste of energy.
Another idea that has come from the research of primates is that monogamy is a way to protect against infanticide. In many species it is common for an adult male to kill the offspring of another male. By pair-bonding, a male is better able to protect his female and their offspring from other, murderous males.
Monogamy In Humans
What you may be surprised to hear is that monogamy in humans is cultural and mating styles are flexible. The majority of human cultures are not actually monogamous. There are cultures in which men have many wives and others in which women take multiple husbands. In still others, having affairs is considered a part of life. Maybe the question of infidelity, then, is one of Western culture and not of evolution.
Many evolutionary scientists agree that we never evolved to practice strict monogamy. We did, however, evolve to develop strong one-on-one bonds. Doing so is important to survival, and an inevitable consequence might be at least some practice of monogamy. When two people become close, it is natural to be able to hurt each other by getting close to others.
To say infidelity is in our genes may not be totally accurate. What is true is that how humans develop relationships and how we behave in them is flexible. It is an important topic to discuss, but the naturalness of cheating should never be used as an excuse to hurt someone you love.