The origin of romantic love and human family life

National Forum, Winter 1996 by Fisher, Helen

Physiological Components

So culture plays a crucial role in whom you find attractive, when you begin to court, where you woo, and how you pursue a potential mate. But parents, teachers, friends, books, movies, songs, and other cultural phenomena do not teach a person what to feel as he or she falls in love. Instead, like the sensations of fear, anger, and surprise, these emotional responses appear to be generated by brain/body physiology. Psychiatrist Michael Liebowitz is specific about this biochemical response; he theorizes that one feels the elation of infatuation when neurons in the limbic system of the brain (which governs the basic emotions) become either saturated or sensitized by natural amphetamines.

"Love is strongest in pursuit, friendship in possession." Emerson has written. At some point that magic wanes. Tennov measured the duration of limerence from the moment infatuation hit to the moment a "feeling of neutrality" for one's love object began. The most frequent interval, as well as the average, was between approximately eighteen months and three years. Liebowitz hypothesizes that the end of infatuation also is grounded in brain physiology; either the nerve endings in the brain become habituated to the mind's natural stimulants or levels of these amphetamine-like substances begin to drop.

Attachment, Liebowitz proposes, is the second physiological stage of romantic love. As attraction wanes and attachment grows, he hypothesizes that a new chemical system is taking over: the endorphins, peptide neurotransmitters that are chemically related to morphine, giving partners feelings of safety, stability, tranquillity, and peace. Neuroscientist Thomas Insel and others have elegantly shown that other neurotransmitters, oxytocin and vasopressin, are associated with attachment, too.

No one knows how long the attachment phase of love endures. But for some people, love ends. There is often a third stage to romantic encounters: detachment. The physiology that accompanies detachment has never been explored. But I suspect that in some long relationships the brain's receptor sites for the endorphins, oxytocin, vasopressin, and/or other neurochemicals become desensitized or overloaded and attachment wanes, setting up the mind for separation. This is not to suggest that men and women are biologically compelled to fall in love, attach, or detach from one another. People regularly maintain long marriages. But divorce is common in societies around the world. And as I collected data on worldwide patterns of marriage, divorce, and remarriage, I came to conclude that the brain physiology associated with attraction, attachment, and detachment evolved as part of our primordial human mating system.
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Does a red fox feel the euphoria of attraction as he leaps to lick his new mate's face during the breeding season in February? Does a robin feel attachment as he gives his mate a juicy insect at dinnertime? Because birds and mammals share many features of brain anatomy, neurophysiology, and behavior, I hypothesize that the biology for these primary emotions, attraction and attachment, evolved in all avian and mammalian genera to coordinate the ebb and flow of each species' specific breeding system.

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Among ancestral humans these emotions evolved specifically to motivate individuals of reproductive age to bond together long enough to rear a singe helpless child through infancy, then to find new mates and breed again. Moreover, as a couple aged, as the length of their pair-bond increased, and/or as a couple bore successive young, these flexible neural circuits helped to sustain pairbonds instead, producing the malleable multi-part human reproductive strategy that is still visible in cross-cultural patterns of marriage, divorce, and remarriage.

With the expansion of the human cerebral cortex more than a million years ago, our ancestors began to build upon this core of primal cyclic reproductive emotions, adding complexity of feeling as well as cultural rituals and beliefs about attraction, attachment, and detachment. And by the time Homo sapiens sapiens people were wearing fox-skin coats and ivory beads and drawing beasts and symbols on cave walls in southwestern France, the Pyrenees, and northern Spain some 20,000 years ago, our forebears had developed an intricate, physiologically based constellation of emotions for loving, as well as elaborate traditions to celebrate and curb what European peoples would come to call romantic love.