Research suggest that humans are serial monogamists.
While we learn from songs, movies and fairy tales that life is all about finding the perfect partner, about romance, soulmates, and lifelong relationships; biology tells us otherwise.
Neuroscientists and neurobiologists have looked at the neuronal correlates of love, using brain imaging techniques and animal models. Reviewing various studies, Dutch researchers explain the evolution and neurobiological factors of our romantic love. Learn what evolution, biological substances and the course of relationships tell us about human relationships. Is romance and monogamy nothing but a myth?
Romantic love is part of the adult attachment system that is evolved to keep parents together for the time necessary to raise the offspring. In the fourth year of marriage, divorce rates in different cultures substantially increase. This can be explained by the “four-year itch” theory of anthropologist Helen Fisher: adult pair-bonds are formed in the four-year period time that offspring is most vulnerable. If a couple has more than one child, this period can be prolonged to seven years. After this time, the couple breaks up to find other partners. This theory suggests that we are serial monogamists, going from partner to partner.
Hormones and neurotransmitters
Romantic love and partnership is influenced by various substances, such as oxytocin, vasopressin, dopamine, serotonin, cortisol and testosterone. These hormones influence the brain in various ways, for instance by activating the reward system, making sex a rewarding experience. Dopamine is one of the neurotransmitters that influences this system, activating the same pathways that are active in addiction. Serotonin, a neurotransmitter associated with various psychiatric disorders, explains why early stages of romantic love show similarities with psychiatric disorders, such as symptoms of anxiety, stress and obsessive behavior.
Much of our knowledge about the role of the hormones oxytocin and vasopressin comes from research on voles (rodents). Prairie voles, with much oxytocin and vasopressin receptors, are monogamous and show preference for their partners. Another species of voles, the montane voles, have less oxytocin and vasopressin receptors. These voles show promiscuous behaviour and do not have a preference for a specific partner. High levels of oxytocin and vasopressin thus play an important role in monogamous relationships.
Romantic relationships evolve over time. In phase 1, there is passion, increased commitment and high levels of stress. After several months to a year, the relationship enters phase 2: the phase of passional love, with feelings of safety and balance, and hormonal factors going back to normal levels. In phase three, after several years, passion decreases, commitment remains high and the love relationship is similar to friendship. Not all relationships make it to phase 3. Some end earlier, due to the 4 years itch, others break up due to lack of intimacy. Some couples however remain in earlier phases, keeping the passion up.
If our brains are programmed to form serial monogamous relationships to raise our offspring, how can homosexual relationships be explained? According to professor ter Horst (University Medical Center Groningen), this is a difficult question: ´ Emotionally a homosexual´s brain will not differ from the brain of heterosexual men or women. Mechanisms controlled by the emotional brain and reward systems are critical for attachment and romantic love and there are no indications that these systems function differently in homosexuals. Research from professor Swaab shows some differences in the reproduction circuitry of the brain. We would like to setup a fMRI study to investigate the brain´s response to a picture of the partner in homosexual relationships to support the hypothesis that the difference is in the reproduction area.´
Happily ever after
Even though research indicates otherwise, some couples do stay happily together lifelong. How is this possible? Ter Horst: ´Although new fMRI studies have to prove this, it seems that the answer lies in sexual satisfaction and spending time together to tune emotional development. Sexual satisfaction in marriage may not be the most important and prime reason to stay together but it may tip the balance when satisfaction is low and rational arguments to stay together are not that strong. One important factor seems to be kissing and hugging. This can be compared to an addiction to the partner. Besides these biological perspectives, there can be personal reasons to choose to stay together for a lifetime. Rational reasons like finance, children or feelings of security might be important enough for marriage and monogamy´.
If you want to have your happily ever after, be an addict, keep your oxytocin levels up, make lots of babies and kiss and hug as much as you can
de Boer A, van Buel EM, & Ter Horst GJ (2012). Love is more than just a kiss: a neurobiological perspective on love and affection. Neuroscience, 201, 114-24 PMID: 22119059