The seeds of the unwelcome separation between man and woman are sown in our first passionate encounter with a partner. In some of us they bloom so rapidly that a "one-night stand" results. In others they take time to yield their unfortunate fruit of separation. Although it offends our notions of romance, a common mechanism, or "biological wedge," drives this separation behavior.

Humans are all subject to the same basic pattern of neurochemical changes that lead up to, accompany, and follow orgasm. The neurochemical shifts governing sex occur primarily in the limbic system of the brain. They are similar in most mammals, and not under conscious control. They have been conserved by evolution because they lead to greater genetic variety and lots of progeny.

This website focuses upon the role of post-coital neurochemistry in disharmony between lovers. We suggest that honeymoons don't last when we allow nature free rein. Post-coital neurochemical shifts alter our behavior and perception, with both short-term and, if a couple stays together, long-term consequences. It is our belief that the neurochemical shifts that set off this nearly-universal "cooling" between the sexes are some combination of the following: the drop in dopamine after climax, the down-regulation of dopamine receptors, the temporary decrease in testosterone receptors, and related surges of prolactin (possibly brought on by the surge of oxytocin at orgasm).

Dopamine and desire

Dopamine is the intensely-exciting neurochemical behind all addictions. Orgasm is the biggest legal blast of dopamine that we can engineer. In 2003 a Dutch scientist, Gert Holstege, announced that his brain scans of orgasm resemble the brain scans during a shot of heroin. But, as Quartz and Sejnowski noted in Liars, Lovers and Heroes, "more is not better" when it comes to dopamine. In fact, rats wired to stimulate (at will) the neurons that dopamine stimulates in the pleasure/reward center buzzed themselves till they dropped, without pausing to eat or investigate sexually-receptive mates. High levels of dopamine are also associated with schizophrenia, gambling addictions and sexual fetishes. See research abstracts on dopamine's role in sexual desire here, and here.

Turning off desire

Not surprisingly, our design includes a self-regulatory mechanism (which encourages us to move our attention to hunting and gathering, and nurturing young). Desensitization to dopamine and testosterone and the neurochemical prolactin each play roles. Among its many tasks in the body, prolactin acts as a sexual-satiation mechanism. It is one of the controls that keeps us from "blissing" ourselves to death, but it only rises after orgasm (and not after sexual arousal without orgasm). Unfortunately, this protective shutdown neurochemistry (prolactin surge, dopamine drop, and related neurochemical shifts) doesn't feel good and makes lovers uneasy - and new potential partners more interesting. Scientists call the natural, neurochemically-induced urge to seek a new partner after frenzied mating with a previous one "the Coolidge Effect."

Prolactin

Prolactin seems to be a major player because high prolactin levels are associated with conditions that couples have complained about since the dawn of time: lower libido, weight gain, hostility, anxiety, and even prostate trouble. Prolactin levels stay high in withdrawing cocaine users for two weeks, and prolactin levels surge in female rats after mating for about two weeks (even if they do not become pregnant). Also, we have personally noticed a two-week hangover of mood swings following conventional orgasm, as have others who have observed themselves carefully. Of course, other neurochemicals may be implicated, but we would wager that prolactin will prove a key culprit in post-passion separation behavior. Prolactin also appears to be a stress hormone - one which correlates with feelings of inablility to control life events. Repeated, seemingly-inexplicable relationship disharmony may trigger the despair sometimes associated with higher levels of prolactin. More on prolactin.

Testosterone

Testosterone influences our libido by activating dopamine in the reward circuitry of the brain. It plays an important role in the libido of both sexes. Experiments show a drastic reduction in androgen receptor density (which decreases the effects of testosterone) in the reward circuitry of the brain following sexual satiation. It may take up to 15 days for laboratory animals to recover their libido fully, which suggests that this shift may play a role in sexual satiety. This occurs even when the blood levels of testosterone remain normal. Relevant research on testosterone.

Neurochemical changes alter perception and behavior

The feelings that result from these neurochemical shifts, which can linger for days or weeks, are projected, above all, onto our intimate partner, and "eventually a man can develop feelings of indifference or hate for his sexual partner." (Taoist Secrets of Love by Mantak Chia). The Taoists teach that this problem is tied to semen loss. However, we believe its roots lie in the neurochemical shifts in the limbic system, and that it affects both sexes. The more intently modern women focus on orgasm, the more they set off the same neurochemical bombs of separation. Surely if orgasm were the key to harmony, we'd be seeing a marked improvement in divorce rates in the last half century instead of the reverse. Modern media regularly touts the benefits of orgasm for its own sake, and yet if orgasm were so beneficial, men would outlive women and porn addicts would be the happiest people on the planet.

The symptoms of this perfectly natural, protective shutdown (unless a new partner suddenly appears) can take many different forms: a "need for space," clingy or needy behavior, uncontrollable attractions to third parties or the use of addictive substances (both of which jack up dopamine levels again), nagging, irrational jealousy, irritability, hyperactivity, apathy, weepiness, susceptibility to porn or "extra-pair bondings" (affairs), and so forth.

Sadly, each attempt to restore our good feelings by raising our dopamine (with another orgasm or a new partner), sets us on another self-initiated cycle of lows…and often an addictive quest for more highs. Pornography, for example, is proving not to be the "harmless eye candy" we've been lead to believe. (See "Help! Porn Addiction in Progress") Heavy users who attempt to quit can experience severe withdrawal symptoms (to say nothing of users' and distortions about women's actual preferences). This hidden cycle of attempting to cope with these natural hangovers by pursuing more and more orgasm may also account for much adolescent distress and the sudden deterioration in the behavior of many adolescents at puberty. Some people suffer such severe symptoms after orgasm that they have dubbed their condition Post-Orgasmic Illness Syndrome.

Above all, there is an unfortunate shift in one's perception of one's partner during this natural hangover period. He or she just doesn't look as good. One doesn't feel as inclined to harmonize with this person, whom one's subconscious [amygdala] is beginning to associate with a recurring post-passion low. At best we attempt to address the symptoms of this built-in separation mechanism through therapy or gaining negotiating skills, but we are not addressing the primary cause. For more detail see Why Does A Lover Pull Away after Sex?"

A program shaped through evolution

Now that church and state can no longer keep us wedded for life, biology's agendas of maximum progeny and genetic diversity are becoming increasingly obvious. (These same patterns appear in traditional cultures, unshaped by Western values, such as the !Kung of the Kalahari and the Mehinaku of South America. Also, no animals are entirely sexually monogamous, although some stick together socially for life.) Our divorce rate is already high, and the percentage of single people is rising sharply.

Genes never sleep. Instead of a blissful "they got married and lived happily ever after," gene fairy tales end with offspring and more offspring - any way the genes can get them. As surely as they drive couples down the wedding aisle in the first place, our genes will push us toward betrayal whenever infidelity is in their interest. Burnham and Phelan, authors of Mean Genes: From Sex to Money to Food, Taming Our Primal Instincts

In his book Sex Time & Power, Leonard Shlain MD pulls into stark relief men's extreme masturbation habits and women's appalling menses drain, as well as our species' proclivity for exclusive same sex pairing, compared with other species. We suggest that all these behaviors are linked to the fact that we are programmed to have sex constantly, unlike species regulated by estrus. Perhaps the natural hangover detailed above creates unsuspected feelings of depletion. These feelings may then show up in our lives as irritability, fatigue, and unusually high levels of friction between the sexes (and/or misogyny and man hating).

Neurochemical balance

Lasting harmony between the sexes may hinge on our learning to overcome the neurochemical separation mechanism outlined above. The radical, yet calmer approach to lovemaking that we recommend appears to increase levels of oxytocin, both in the body and in the brain, where it encourages monogamous behavior. (Scientists first discovered a key neurochemical component of monogamy by studying the effects of oxytocin and vasopressin in prairie voles' brains.) Certainly, oxytocin levels correlate with nerve growth factor (NGF) levels, and NGF levels are associated with "in love" feelings.

Higher levels of oxytocin would also account for the decrease in cravings, and the health improvements noted by sages of the past who also recommended this less-driven way of making love. Recent research suggests that heart-centered behavior may also moderate testosterone levels in men.

Oxytocin counteracts stress and, therefore, depression as well. Yet the situation is confusing because oxytocin usually rises briefly at orgasm. However, researchers have suggested that its function at that time may be simply to set off the smooth-muscle contractions of orgasm and even post-orgasmic prolactin surges, not to bond us.¹

The good news is that we have another hidden mating program, which we share with only five percent of all mammalian species. We find pairing up with a trusted companion very rewarding...at least for a while. As the ancients discovered, we can steer for the bonding behaviors that activate and sustain this program. At the same time we can stop emphasizing the sexual satiety that leads to habituation, in favor of a gentle, equally satisfying approach to lovemaking. Using these two "pedals," those of us who would like to sustain our relationships can free ourselves from biology's plans for our love lives.

In our lifetime, global population has risen from 2 billion to 6 billion. Since humankind is well on the way to overpopulating itself into extinction, it may be time to give serious consideration to an approach that allows couples to find deep satisfaction while decreasing the risk of carelessly-conceived progeny.

Visit this page to find abstracts on the neurochemistry sex, mating and evolution. Relevant articles from the general press can be found here. Links to some of our articles can be found in the left-hand menu, and below.