Centuries ago, love was considered an inane reason for marriage in Western societies. Women were encouraged, if not forced, to consider a man’s wealth and standing far more than his personal qualities. Men treated their wives as property, finding passion and romance in adultery rather than in matrimony.
Today, love and marriage are so intertwined that we generally accept them as civil rights. People are delaying marriage more than they did in any other generation – in part to establish careers, and in part to increase the likelihood of finding the ideal mate. Neuroscientists, however, are finding that marital success hinges to a significant degree on, of all things, biological factors.
Studies of twins enable psychologists to parse out heritable influence from environmental factors when studying marital satisfaction. Among the initial findings is that if one twin enjoys a happy marriage, the other is likely to do so too. A study of 1,500 identical twins, who share the same DNA, revealed that they were more likely to both be divorced than fraternal twins who have only half the same genes. Another study reported that identical twins are more likely to both have married than is the case with fraternal twins.
There is a specific gene that affects bonding behavior. Alleles in men appear to affect the health of their marriage. A study of 552 heterosexual twins showed that those who carry a variant of the gene, allele 334, were more likely than non-carriers to have experienced a marital crisis or threat of divorce in the prior year. In fact, men who carried two copies of the allele were more than twice as likely as non-carriers to report marital difficulties. Women married to men with one or two alleles scored significantly lower on marital satisfaction than did women who were married to men without the allele. Those women described their partners as less physically affectionate and more disagreeable.
Allele 334 is not the only gene that influences marital harmony. There is also a link between relationship fulfillment and a gene variant known as 5-HTTLPR found on the serotonin transporter gene. All of us inherit a copy of the gene from each parent.
The 5-HTTLPR allele comes in two major variants – short and long. Research shows that those of us who inherited two short alleles have a heightened emotional sensitivity to the ups and downs of long-term relationships. Those of us with one or two long alleles are far less bothered by the emotional tenor of our respective marriages.
Research is now looking at environmental conditions that can counter one’s heritable risks for breaks in the ties that bind.
ReferenceSleek, Scott (2014). Genetically ever after. The Observer, Association for Psychological Science, 27, 15-17.