Cheating is a fact of life. Monogamous relationships in the animal world are not really monogamous. About a quarter of the high offspring in the nests of socially monogamous birds such as barn swallow are raised by males other than the second.
In a previous article, It’s argued that infidelity is also part of the human heritage.
But why? If a man or woman is unhappy with one aspect of his lover or spouse, why did he agree to quarrel with them in the first place?
Not long ago, this would have seemed an easy problem for researchers. For women, the main advantage of infidelity was better genes for their offspring with the added benefit of the gifts provided by the lovers. For a man, the advantage was simply spreading his genes or making more children.
In recent years, these two theories have been thrown on the rocks of skepticism and contradictory evidence. As for the masculine explanation, this only works if men differ widely from each other in the number of children they generate. Again. Recent data on subsistence human societies contradict this point of view: men’s reproductive success is no more variable than that of women. Ultimately, maximizing the number of children born was not a viable reproductive strategy ( unconscious ) for men. One plausible reason is that fathers were much more important in nutrition young children that anthropologists did not think.
The female justification of infidelity was simpler. A woman who threw her lot with the best man available had doubts when she saw the carved figure of a natural athlete. She gave in to temptation and her offspring benefited from better genes.
Farewell to the theory of good genes
The key problem with the theory of good genes is that no one has ever been able to determine exactly what makes genes good. If there is a lot of food, it is good to look like Mr. Universe, but most local ecologies are too poor to support this kind of physics and a much lighter construction is found for men in most societies of subsistence.
Any gene that is good for an environment can be a liability if the environment changes. Perhaps this is why the evidence about good genes is so disconcerting that I pointed it out in my article on the tale of the peacock.
Even if there were really good genes, and if the females preferred to mate with males with these good genes, then the bad alternatives would multiply and all the males should have good variants.
Cheating for Parasite Resistance
One aspect of good gene theory that appears to be relevant to animal research is the view that females choose males that are resistant to local diseases and parasites.
This theory seems to hold up for women too. In societies where parasites are prevalent, women are more interested in the physical attractiveness of a man. They are also more interested in casual sex, suggesting that one of the reasons for infidelity is to gain better immunity for their children.
Another fairly obvious advantage of infidelity for women is to seek a new permanent partner and women generally engage in extra-marital relationships when they are dissatisfied with the emotional quality of their marriage.
Sauce for the jars
Here for women! Why do modern men engage in extramarital sex if it is not particularly likely to increase the number of descendants raised by their ancestors? There is little evidence that dissatisfaction with their spouse motivates men to cheat to initiate a new marriage.
Men can be sued by women who intend to supplant their spouse, of course. Otherwise, there are two plausible male motives for cheating – the desire for sexual variety and the attraction for younger, more fertile women. The first seems to be reproductive opportunism, but the second might reflect the psychology behind selecting a long-term partner.
Men are interested in unattached sex, but cheating alone is not a viable reproductive strategy. The reason is that the vast majority of women resist this.
Where do People Look for Partners?
People often will seek out new men online through dating sites that are made for cheaters. You can read more about these sites if you want.
The anonymity of the internet makes it easy to find a lover. There are even smartphone apps like tinder which you can read more about here. These apps allow people to find affair partners in the privacy of their own home.
Overall there is no definitive answer why people cheat so much. Most of it will do with the Coolidge effect and that people get bored of their partners after awhile.