How do you explain fidelity and infidelity?

Many people want to be loved by one and only one person. They feel attachment to only one person. They have promised to be faithful to one person. It is cheating to break such promises. We feel jealousy when our partner seems attracted to someone else.

Practically speaking, if one person in a couple is free to do it, then both members of the couple should be free to do it. Both parties should behave in the same way. It hurts other people if you are unfaithful. It hurts the spouse, the children, even the community.

From the point of view of evolutionary biology, the male strategy for passing genes on is to spread their seed as far and wide as possible. The female strategy is to bind a partner to her (not necessarily the biological father of her child), in order to help raise the child.

There are mental health explanations: so-called sex addictions. Or love addictions.

However, many people do “cheat.” I don’t know how many, and I don’t know if it’s measurable. I do know that half the marriages in the US end in divorce, and that a lot of times the reason for the divorce is cheating. There are also polyamorous groups who openly sleep with more than one partner. These days, there’s the idea amongst young people of “hooking up,” which seems to involve multiple short term partners.

Yet, despite all this behavior, it seems to me that there is a strong cultural disapproval of having multiple lovers. At best it is seen as a hedonistic thing indulged in my the upper class or intellectuals, and at worst it is seen as something that should be punished by death (well, if you’re a woman).

What’s going on here? Why do some people (and perhaps many people) behave in hypocritical ways? Are we all following our biological natures? Are many of us immoral creatures? If we were truly religious, would things be better? Are there really sex addictions? Is it personality? Improper upbringing? How do you explain fidelity and infidelity?