Dr.
Theresa Crenshaw puts it, “when you fall in love or in lust it isn’t merely an emotional event. Your various hormones, each with unique features to contribute, get in bed with you too.”3 Dr. Helen Fisher divides love into three categories that correspond to different hormones and brain systems. Her analysis of the data suggests that high androgen and estrogen levels generate lust, romantic love correlates with high dopamine and norepinephrine and low serotonin, and attachment is driven by oxytocin and vasopressin.
To make matters more complicated, these three systems interact. For example, testosterone can “kickstart the two love neurotransmitters while an orgasm can elevate the attachment hormone,” according to Fisher. “Don’t copulate with people you don’t want to fall in love with,” she warns.4
Scientists also tell us that the intensity of romantic love that many couples experience early on, which is fueled by endorphins, naturally diminishes after a couple of years. Oxytocin levels then support a few more years of attachment, rising with the birth of each new child, perhaps accounting for worldwide peaks in divorce rates after four and seven years of marriage as bonding between partners loses some of its biochemical boost.
If affectionate touch, sexual activity, and orgasms also decline over time, oxytocin levels will further decline.
Vasopressin, which has been called “the monogamy molecule” because it’s been identified as the cause of lifelong mating patterns in male prairie voles, has also been implicated in human bonding. Swedish researcher Hasse Walum5 reports that in a study of 552 pairs of male twins, those with a gene reducing the effect of vasopressin scored lower on a psychological test measuring bonding. The women they were married to also reported lower levels of marital quality. As a result, there has been speculation that vasopressin levels may play in a role in determining whether a man is monogamous.
Marnia Robinson, author of Peace between the Sheets , advocates that both men and women withhold orgasm during sexual exchanges to short-circuit the brain circuitry, leading to a decline of interest in a partner once they’ve habituated to each other. She theorizes that the human 1 2
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brain, unlike the bonobo brain, is wired for pair bonding with a specific type of dopamine receptor that creates addictive-like cravings for one’s mate. But as with any physical addiction, the “fix” loses its potency over time. Robinson speculates that by withholding dopamine-releasing orgasms while increasing oxytocin-releasing touch and affection, bonding can prevail over the “craving” for new and different sexual stimulation.6
If Robinson’s hypothesis is correct, it goes a long way toward explaining why women, who are generally less likely than men to reach orgasm through intercourse or to reach orgasm at all if their lover is unskilled, are reputed to be more likely to remain attached, while their male partners seek variety.
While love, sex, and relationships are clearly influenced by many factors in addition to genetic variations, hormones and neurotransmitters, and pharmaceutical and recreational drugs, most experts agree that we would be foolish to ignore the role of biochemistry.
IS INFIDELITY MONOGAMY?
Is infidelity monogamy? What about serial monogamy? These may sound like silly questions, but with as many as 70 percent of all couples experiencing extramarital affairs, monogamy has been redefined. Most of these couples consider themselves to be monogamous, as do couples who divorce and remarry others. Clearly, their behavior does not match their identities.
As long our society stigmatizes people—and especially women—who tell the truth about their nonmonogamous desires and activities, it’s likely that people will choose more acceptable labels even if they are misleading to say the least.
According to the 1999 U.S. Census, almost half of all