MOST of us know that obsessive, butterflies-in-the-stomach feeling; how it is to be in love. But have you ever stopped to think about what love is for? Why would evolution have furnished us with an emotion that at first sight seems ridiculously maladaptive – in the first throes, it makes us useless and unable to think about anything other than our new love.
It might induce us to make huge sacrifices for that other person, spend vast amounts of money on them, or even risk our own life for them. What's more, it makes us oblivious to all the other potential mates out there who might be sexier/richer/more intelligent than the object of our affection.
So why don't we all just behave like our close relatives the chimpanzees, whose trysts rarely last for more than a few days and often for only a few minutes?
Actually, yes, some people do behave like this some of the time. OK then, so why is it that pairs of people often manage to stick together for long periods of time in a mutually supportive relationship?
The answer to the conundrum is that, unlike chimpanzee infants, human children through evolutionary time were much more likely to survive and breed themselves when they had two parents to look after them – so basically, love evolved because we needed something to help us stick together for the sake of our contribution to the gene pool.
There is plenty of evidence that children do better with two parents in traditional hunter-gather societies, but also even today in the UK, according to research by Daniel Nettle of Newcastle University. His work demonstrates that children whose fathers are involved in their upbringing tend to have higher IQs and greater upward social mobility (see The Scotsman, 20 September 2008).
But if it's such a good idea to stick together in pairs, why can't we just make a rational decision to do that? Why do we need love? Economist Robert Frank says in his book Passions Within Reason, that we need irrational love to trick us into making the right choices for our own long-term benefit. He says that we tend to be more attracted to immediate rewards than larger, more distant ones.
For instance, extramarital affairs give instant gratification, but this may well be outweighed by huge costs at a later stage if the main bond breaks as a result. Frank suggests that when you love someone, the emotional cost of betraying them is experienced right away and could outweigh the immediate attractions of an affair. Love also makes it easier to ride out rocky patches in a relationship, such as financial woes or illness.
This idea is supported by results of research by Gian Gonzaga of eHarmony and his colleagues at UCLA. They found that the greater the amount of love someone said they felt for another, the better they were at resolving conflicts with that person. They also tended to make better long-term plans together, taking into account the wishes of their partner.
Love also communicates to the other person how you feel about them, and that you are committed to them, says Gonzaga. It does this through a number of signals that are hard to feign. These include head nods, leaning towards the partner, positive gestures and Duchenne smiles – that is, smiling with the eyes as well as the mouth – and this, says Gonzaga, is almost impossible to do if you don't love the other person. "Evolution has created behavioural expressions that are very, very difficult to fake unless you're genuinely feeling that emotion," he says.
But, of course, if the emotional bond in a partnership is going to last so that we can successfully raise a brood, we've got to be able to resist the temptation to trade up our partner every time some other potentially attractive option comes along. We have to be blind to all but our beloved.
Gonzaga and his UCLA co-workers carried out some experiments in which they found that being in love appears to help us to be just that. The scientists had 60 men and women, who were all in committed relationships, pick out photos of very attractive people of the opposite sex.
They then divided the subjects into three groups and got them to write essays: one group wrote about a time when they felt most love for their partner, another group about the time when they felt most sexual desire for their partner and the third group wrote about anything they felt like writing.
It turned out that the 'love' group were far better able to suppress thoughts about the attractive 'alternatives' in the photos than the 'desire' or control groups, and those in the 'love' group remembered fewer details about the attractiveness of the photographed models – although they were able to remember other details, such as what they were wearing.
"It seems like this experience of love actually changes your attention, then also gives you the ability to push any threatening thoughts for that relationship away," says Gonzaga.
But do we still need love nowadays with the changing social situation? Women are becoming increasingly financially independent, presumably making fathers somewhat less vital for the actual survival of children, although clearly they can be important for their offspring's well-being. Could natural selection, then, get rid of love?
"If it's going to be selected out it's going to take a couple of hundred thousand years," says Gonzaga.
He points out that romantic love is part of a broad suite of commitment in humans that also includes maternal love, and family love which orientates people towards their own kin in times of need.
"Humans are really driven as a social species," he says. "It's difficult for me to imagine how they could evolve in the opposite direction."
Love, it seems, is here to stay.
WHAT LOVE CAN DO FOR YOU…
LOVE IS GOOD FOR YOUR HEART
A STUDY at the University of Pittsburgh found that happily married women have very much lower risk of cardiovascular disease than those in stressful and troublesome relationships. Also, talking to someone you find attractive sends impulses to the heart, making it pound three times faster than normal, which increases blood supply to the body.
LOVE MAKES YOU LIVE LONGER
THE National Longitudinal Mortality Study in America found that married people outlive unmarried ones. Married people are also less likely to get pneumonia.
LOVE CAN HELP FIGHT CANCER
A UNIVERSITY OF IOWA study discovered that ovarian cancer patients in happy relationships and with a strong connection to others develop more white blood cells, which help kill off cancerous cells.
LOVE DE-STRESSES YOU
HAVING sex twice a week decreases your stress levels significantly and also promotes intimacy and emotional satisfaction. Men having sex that regularly are less likely to die over a ten-year period than those who have sex less than once a month.
LOVE CAN MAKE YOU SMARTER
FALLING in love induces a calming effect on the body and mind, which in turn raises the body's levels of nerve-growth for about a year. This can help restore the nervous system, and improve memory by triggering the growth of new brain cells.
LOVE CAN KEEP YOU LOOKING YOUNG
ENDORPHINS produced when you are in love will increase the amount of blood flowing to the skin, which in turn helps keep it soft and smooth, reducing the chance of wrinkles developing. It will also give your face a pinker, healthier glow. Research shows that couples who have a healthy sex life can look up to seven years younger than those who aren't as intimate – possibly because sex reduces the external signs of ageing caused by stress.
LOVE IS GOOD FOR YOUR IMMUNE SYSTEM
RESEARCH shows that loving acts neutralise the sort of negative emotions that affect the immune system, as well as endocrine and cardiovascular function.
LOVE LOWERS YOUR BLOOD PRESSURE
DOCTORS at the University of North Carolina discovered that hugging may dramatically lower blood pressure and boost blood levels of oxytocin, a hormone that plays a key role in labour, breastfeeding and orgasms.
LOVE CAN REDUCE YOUR CHOLESTEROL
A STUDY in Human Communication Research showed that expressing your feelings can reduce cholesterol levels. The study found that people who wrote about their feelings of affection for significant friends, relatives, or romantic partners had significantly lower cholesterol levels than those who didn't.