What is love? Well, according to Shakespeare’s Romeo, it’s a smoke raised with the fumes of sighs and a madness most discreet. Robin Dunbar, a professor of evolutionary anthropology at Oxford University in the UK, is a little less poetic. He believes love is an evolutionary mechanism that allows humans to bond long enough to raise children to a survivable stage. Love, according to this scientific theory, is a biological trick conjured up using neurological reactions to different chemicals released in the body.
Prof Dunbar explains, “We evolved the capacity for love because evolution is interested in the number of descendents you leave and a mechanism that causes you to bond successfully with another individual and raise your descendents is essential to the evolutionary process.
“[Unlike other animals], we have big-brained offspring that need a high level of parental
care, so as a species we need some mechanism that allows pairs to stay together over a longish term.”
According to Prof Dunbar, in evolutionary terms love developed because our species gained the ability to walk upright. That vital landmark created a problematic design fault as human babies with their big heads are hard to exit through the complicated design of a biped pelvis. So evolution made a trade off. In order to transit safely through a female pelvis, human babies are born earlier in developmental terms than other animals. To put it in context, it takes a human baby 21 months after birth to reach the same developmental stage as a newborn chimp. Our babies are helpless and totally dependent on us for several years. As a result, parents need to co-raise their offspring and in order to stay together to do this they need a high level of attachment. The mechanism that encourages this attachment is love. Thanks to an increasing understanding of the inner workings of the brain, scientists now have a concrete idea of the components that make up love in the human brain and how they interact.
Dr Helen Fisher, a biological anthropologist at Rutgers University in the US, proposes that there are three distinct stages to love and that they are each governed by a specific set of hormones and neurochemicals. The first stage is lust, and hormones testosterone and oestrogen work here to fuel our desire to find a mate.
Next, neurotransmitters called ‘monoamines’ work to generate an attraction between lovers. During this stage, dopamine stimulates the ‘desire and reward’ mechanism in the brain by triggering intense rushes of pleasure. Fisher suggests, “Couples often show the signs of surging dopamine, increased energy, less need for sleep or food, focused attention and exquisite delight in the smallest details of this novel relationship.” Norepinephrine or adrenaline is also released and serotonin levels are lowered, which causes obsessive thinking.
The final stage is attachment, which is heavily reliant on oxytocin, the chemical released during breastfeeding, which helps mothers bond with their children. It is released by both sexes during intimate moments and is thought to promote bonding.
Vasopressin – a hormone whose primary function is to retain water in the body and to constrict blood vessels, but which also plays an important role in social behaviour, bonding, and maternal responses to stress – is another important chemical that is released in the long-term commitment stage as are endorphins, which have an analgesic effect and generate a sense of numb well-being.
Using functional magnetic resonance imaging technology, scientists have even been able to map the areas of the brain where love happens. In 2001, experiments conducted on people in the early stages of love revealed that the sensation of romance is processed in three areas. The first is the ventral tegmental in the brain’s lower regions, which is the body’s central refinery for dopamine. Fisher and her colleagues have conducted recent fMRI scans of people who are not just in love but newly in love and have found that their ventral tegmental areas are working particularly hard. “This little factory near the base of the brain is sending dopamine to higher regions,” she says. “It creates craving, motivation, goal-oriented behaviour and ecstasy.”
The nucleus accumbens, located slightly higher and further forward than the ventral tegmental, is then believed to turn the exhilaration of a new partner into what can approach an obsession. The last major stops for love signals in the brain are the caudate nuclei, a pair of structures on either side of the head that store patterns and habits. It is believed that in this region early passion is hard-wired into enduring commitment.
However, despite the knowledge we have of the processes involved when we fall in love, scientists doubt that we will ever be able to create fake love as we are still a long way from fully understanding the interplay between all of love’s biological facets.
Prof Dunbar also doubts that we can train ourselves to love more. “My gut feeling is that no, there is probably some kind of age limit on developing the capacity to love,” he says. “When that would be is another matter. I wouldn’t be surprised if the cut-off point for the development of emotions and emotional responses such as love was quite early, between five and the end of the teenage period. After this they become automated responses.”
Despite its scientific complexity and long evolutionary trajectory, love can be deeply flawed. This in part is because the combined effects of the neurochemicals released as we fall in love help to mask reality.
“You don’t do reality checks when you are in love, which is why online dating scams work,” says Dunbar.
He believes there is a solid reason for this – the hunt for Mr or Mrs Right can be long and fruitless and get in the way of procreation. Humans do not produce large numbers of young and so, to encourage mating, need a mechanism that encourages them not to be too choosy when searching for a mate.
“When you meet someone you are attracted to, you exaggerate the details you like and forget about the details you don’t,” says Dunbar.
“The problem comes when you put that machinery into an environment where it wasn’t meant to be, such as online dating. You look at the cues, the picture or the brief words you are sent and you invent the rest. You have no reality check. In the online world it takes a long time to meet face to face and so the longer the communication goes on, the more exaggerated your invented reality becomes. You paint this picture of a person so heavily that by the time reality catches up with you, it is harder to undo it and you have started to commit yourself so the relationship is difficult to get out of.”
While the love response encourages us to stay with a partner, other behaviours allow us to test whether we have chosen the right partner biologically. Kissing is a key selection process. Sheril Kirshenbaum, a biologist from the University of Texas and author of The Science of Kissing, believes that in adulthood, kissing has multifaceted purposes. When a woman kisses a man, she can gauge his suitability as a mate by picking up on his hormonal markers.
Kirshenbaum explains, “Our sense of smell tells us a lot about other people and whether they may be a potential partner and even a genetic match. It happens on a subconscious level. Women have a stronger sense of smell and taste and when we are kissing we use the information we get from our senses. It is nature’s ultimate litmus test.”
Endocrinologists have found that through kissing, women can sample a section of a potential partner’s genome called the major histocompatibility complex (MHC). The MHC is related to the immune system and women are attracted to the scent of men with a different MHC to themselves.
“The advantage is that if you pair up with someone who has a diverse MHC, your children will be healthier and more likely to survive,” adds Kirshenbaum.
And for those this Valentine’s Day who worry that breaking love down into its scientific constituents strips away its magic, Dunbar, a self-confessed romantic, has these words of comfort, “Understanding a process doesn’t actually change how you experience it. It can make it even more interesting.
“At the end of the day no amount of scientific understanding is going to change your experience of love. It is automatic.”