In the movie Moonstruck, Rose, the Olympia Dukakis character, asks why men want more than one woman. She comes to the conclusion that it is because they fear death. That may not be the right answer. It may not even be the right question. We are not a naturally monogamous species, and there are evolutionary pressures on males not to be sexually faithful. Understanding infidelity is not the problem. The problem is what to do about it.
Are we really not naturally monogamous? An estimated 45-55% of married women and 50-60% of married men engage in extramarital sex at some time or another during their relationship. (The figure is quoted by Joan D. Atwood and Limor Schwartz, Journal of Couple & Relationship Therapy, 2002)
There are clear evolutionary reasons for men to be unfaithful. Any genetic tendency towards having sex with more women would increase the presence of those genes in the gene pool. That is precisely what evolution selects for.
The mechanisms by which this works include (as men report) becoming "bored" with a relationship with one partner and a felt need for "variety."
To men sex and commitment are separate things. One way men have evolved to increase their genes in the gene pool is by being committed to a family and to raising their children to maturity. Another way is by having sex with many women. Both of those tendencies are present simultaneously.
Powerful, successful men are inclined to have multiple sexual partners. Consider other mammals, like elk. There is no question why the males compete. The winner gets the harem. Isn't it likely that the success drive in men evolved for the same reason? Extra resources for a few offspring wouldn't have as much selective advantage as having as having a great many offspring.
Successful men think they have it coming to have more sexual partners. Indeed, the more successful they are, the more women who want to have sex with them. Some women make it a project. Consider Alma Maria Mahler Gropius Werfel who became wife or mistress of many of the important creative men in Vienna.
What should you do if your husband is unfaithful? It depends much on his infidelity's meaning. Don't rush to take it personally. It may be more about him being a man than it is about you or your relationship.
What commitment do you want? A man is capable of being committed to a marriage even if he strays occasionally.
If you expect perfection against strong evolutionary pressure to the contrary, you are likely to be disappointed. You can't even get him to clean up after himself, and there is no particular natural selection for messiness.
Infidelity is an occasion for a discussion of commitment to your relationship and its problems. Other than just from being men, men often stray because they are unhappy with their wives or having difficulties with their relationships.
These discussions are difficult for men. They do not have much expertise in thinking about relationships or discussing feelings.
When a man commits, he commits to a particular, attractive woman who admires and values him. After marriage, women change. They typically gain weight. They try to change their husbands by pointing out their flaws. The reasons for the initial commitment erode. A new woman who is admiring and attractive is, well, attractive.
To retain commitment, it helps to understand that men respond to Femininity and to individual women who understand and appreciate them. If your behavior displays the grace of femininity and you understand and appreciate him as a man, you will be able to retain his commitment, even if not always his perfection.
To read more on male sexuality and how to define infidelity for men, visit the Tips What Men Want site, http://tipswhatmenwant.com/ created by Thomas Christopher, a Colorado Front Range public speaker on relationships.