Your Cheating Heart: The Science of Adultery

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Your Cheating Heart: The Science of Adultery
By Heath Shive

It is hard to get a lock on adultery statistics.  For accuracy, everybody would have to tell the truth, right?  Good luck with that. 

The anthropologist Helen Fisher – one of the nation’s leading experts on adultery – reports some adultery statistics from her book, “The Anatomy of Love.”

• In the 1970s, a Morton Hunt survey reported that 41% of men (out of group of 691) and 25% of women (out of 740 surveyed) had cheated on their spouses
• The National Opinion Research Center in Chicago reported that 25% of American men and 15% of American women cheat sometime in their marriage
• Some other studies indicated numbers ranging from 20% to 50% of all married people will cheat

During an interview with journalist Neil Strauss – part of his book “The Truth” – Helen Fisher personally gauged the odds of a man or woman (under the age of 40) cheating…to be about equal!

But why cheat?

A behavioral psychologist might point to boredom, mistrust, revenge, or need for validation.

But evolutionary psychologists think adultery is written on your DNA, and there’s (some) science to back this up.

To the science! 

The Pair-bond of Prairie Voles

Prairie voles are famous for mating for life. 

When two prairie voles first mate, the sex triggers oxytocin receptors in females and vasopressin receptors in males.  Dopamine is released into the brain in such a way to create a pair-bond, which lasts most voles for life!

Viva amore!

But in some voles, the genes governing the vasopressin system are variable, which also varies the strength of fidelity.    

Humans have similar genes in the vasopressin system.  In 2008, researchers studied the effects of these genes in a group of 552 “twin pairs and their spouses.”  All of these participants had been in a relationship for at least 5 years; 82% were married and 18% were cohabitating.    

Men who inherited this gene variation (the 334 allele) scored significantly lower on the Partner Bonding Scale – a questionnaire that measured one’s degree of mate attachment.  Men carrying two copies of this gene showed the lowest scores on the Partner Bonding Scale.  Men who had no copies of this gene were the most attached to their partner. 

Men carrying this vasopressin gene variation had also experienced more marital crises during the previous year – twice as frequently as men without the variation. 

Far from exhaustive, this study only included about 1,889 DNA samples, all from only one country (Sweden).  And the study didn’t measure infidelity directly. 

But the study did suggest a biological connection that could contribute to cheating.

Other Studies Too

In a recent study of 181 young men and women, biologist Justin Garcia and his colleagues found a direct link between specific genes in the dopamine system and a greater frequency of uncommitted sexual intercourse, largely one-night stands, as well as a higher frequency of sexual infidelity. 

The Sins of the Parents

If there is a genetic contributor to adultery, it might be inherited.  And adulterous – or polygamous – people are successful from a Darwinian standpoint.

In other words, they have more children. 

For example, the legendary Moroccan sultan Ismail Ibn Sharif is alleged to have had 867 children, the result of having a harem of 2,000 concubines!  Furthermore, 84% of all human traditional societies permit a man to take more than one wife at once – polygyny.

Conclusion

Romance gave us star-crossed lovers.  Is science suggesting gene-crossed cheaters?

According to my genes, my eyes aren’t that strong and I started to get gray hairs this year.  But I wear glasses and I can dye my hair.

Your genes are not in control.  You’re the pilot; the genes are just along for the ride.  And one thing’s for sure.  If you cheat, you’re going to have a bumpy ride. 

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Sources:

Fisher, Helen. Anatomy of Love: A Natural History of Mating, Marriage, and Why We Stray. Rev. Ed. W.W. Norton & Company, 2016.

Garcia, J.R., J. MacKillop, E.L. Aller, et al. 2010. Associations between the dopamine D4 receptor gene variation with both infidelity and sexual promiscuity.  PLoS ONE 5: e14162

Strauss, Neil.  The Truth: An Uncomfortable Book about Relationships.  Dey St, 2015

Walum, H., L. Westberg, S. Henningsson, et al. 2008. Genetic variation in the vasopressin receptor 1a gene (AVPR1A) associates with pair-bonding behavior in humans.  Proceedings of the National academy of Sciences 105 937): 14153-56. 

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