We have long been confounded by that indescribable phenomenon known as love. For millennia it has been the muse of painters, poets, musicians and romantics alike, each attempting to describe love in its most raw state, to rationalize the clearly irrational. It doesn’t take an Einstein to appreciate that not all love is the same. For example, the love you feel for a friend, family member, or romantic partner are all distinctly different. In fact, love is so capricious in nature that the Greek philosophers came up with eight different words to describe the range of emotions we commonly experience.

However, high-minded our philosophical stance, much of this introspection has been motivated by our desire to better understand the secret behind romantic love, Eros. Ancient apothecaries (or at least their clients) have invested heavily in the creation of lotions and potions intended to manipulate our hearts. After millennia of speculation by practitioners of ‘the arts,’ charlatans and dreamers, it is the turn of science to throw its cap into the ring. Could it be that those apothecaries were right and love is nothing more than a simple cocktail of pharmaceuticals?

Since the enlightenment, the consensus has been that man’s superiority over the earth and its kingdoms was a consequence his ability to tame our inner beast, that our mastery over heaven and earth was a consequence of a cerebral way of being. However, love is the battlefield where nature is giving nurture a thrashing. In the words of the comedian Tim Minchin, “We’re just f$%ing monkeys in shoes.” Even this statement is overly kind to your inner love-monkey. Yes, birds do it, bees do it, even educated fleas do it. And with any system that has had millions of years to fine tune itself on the treadmill of evolution, love, shall we say romantic love, is simple, animalistic and irrepressible.

Hard science has taken over where Stendhal's theory of crystallisation (an imaginative readiness for love, which only needed a single trigger for the object to be imbued with every fantasised perfection), Proust’s ponderings on inaccessibility and jealousy and Lacan’s whimsy (love is giving something you haven't got to someone who doesn't exist) have failed. In the face of modern biochemistry and functional magnetic resonance imaging we leave Spinoza, Freud and Jung scrabbling in the dust. In short, biochemistry has proven that we're ‘hard-wired’ (at least chemically susceptible) to love. And that, when nature ‘guns’ her throttle we can sustain romantic love to maintain a successful marriage and the family unit, thanks to neurotransmitters like dopamine and a suite of genetic mutations.

It appears that love is a series of receptor-binding episodes, providing a contiguous journey that can be split into three distinct components – desire, attraction and attachment – biochemical programming that has us willingly contribute to the safe delivery of the next generation.

Desire

Dictionaries tell us that ‘desire’ is a strong feeling of want or wishing for something to happen but in reality it might be better expressed as ‘longing’ or ‘craving’ – what we might colloquially call lust, or more politely libido. The first sparks of love are born of the surge in androgens and oestrogens as we become sexually mature, instilling feelings that demand we seek out a significant other. Testosterone appears to be a major contributing factor to sexual motivation in males. Oestrogens and progesterone typically regulate motivation to engage in sexual behaviour in females (although the relationship between hormones and female sexual motivation is not as well understood). Nevertheless, the peri-ovulatory period of the female menstrual cycle is often associated with increased female receptivity and sexual motivation.

Attraction

The initial feelings of attraction are a consequence of three chemicals in the brain: noradrenaline that has you dumping systemic adrenaline into the body causing that racing heart and sweaty palms; dopamine, the feel-good chemical; and phenylethylamine, released when we’re near our crush, giving us butterflies in our tummies. But is there a biological reason behind these feelings? And why you end up making one person the object of our dreams?

Although androgens and oestrogens fuel the sex drive, mother nature is an old romantic at heart and not just anyone will do. She knows that the course of true love never runs smooth and she wants you to seek out and capture ‘the one’, that singular partner most likely to match our specific immunological profile (with the aid of highly individualised pheromones) to ensure the healthiest progeny on mating. Physical chemistry is generally the instant spark that draws you closer to a person. This chemistry is something that does not include your intended partner’s hobbies, habits or personality – it is solely based on appearance.

But this isn’t like the movies where you fall in love with a person at first sight. Physical attraction is only the first step. Beauty is in the eye of the beholder but just how important is it? There are several ways in which appearance has a subconscious impact on your choice. For example, having a symmetrical face is generally considered a hallmark of conventional attractiveness.

Studies have found that having a symmetrical face implies the presence of ‘good’ genes, while an overly lopsided face may imply poor health, alcohol abuse or smoking. Meanwhile, in men, having a longer ring finger (versus the index finger) is an indicator of higher testosterone, and therefore a higher sperm count, increased fertility, a healthier heart and ‘better’ genes. However, your brain also takes into account your own life experiences, which is why your preference and taste in appearance is very much unique to you! Studies have found that who we find attractive is strongly influenced by factors like the kind of faces you are exposed to and the relationships you form. For example, having an early positive relationship with someone can have you subconsciously imprinting their facial characteristics with positive information. Subsequently, people who look similar you consider more attractive. Research also suggests that familiarity and exposure to certain faces increases their attractiveness. Do you really always marry your mother? We certainly prefer faces that are similar to those we’re more familiar with. Nature appears to have a mechanism that rejects outsiders.

Traditionally, a waist-hip ratio of 7:10 has been held up as the ideal for feminine attractiveness, while women look for a man with a waist-to-hip ratio of 9:10. It’s also important to have a healthy body mass index (BMI). Apparently, men find women with a BMI of 18 – 20 most attractive, as it indicates both good health and fertility. Meanwhile, women are subconsciously looking for a man with body fat of around 12% – probably because a high body fat content is associated with heart disease, diabetes and reduced fertility.

In reality, you have to sniff a lot of frogs before you find your prince. This can be exhausting and to keep you ‘out there’ until you can ‘lock-on’ to that perfect target of your desires. Surging levels of adrenaline induce a stress response, which is one reason you may clam-up or suddenly forget what to say around your crush. Spikes of dopamine cause a euphoric attitude and a figurative ‘high’ within the brain. The chemical cocktail is what causes love struck people to become fixated on individuals. The region affected by the explosion of dopamine is also the area that shows activity when experiencing the rush of cocaine. The obsessive, intrusive thoughts about the person you ‘love’ are due to the lowering of serotonin. Nearly 65% of a lovestruck person’s day is spent thinking about the object of their infatuation once they are in the-zone.

If you’re female, your choices are linked to the health options of your future progeny. In one study, female participants were asked to rate the smell of several T-shirts, slept in by various men, women preferred the scents of men who had disease-resistance gene profiles that complemented their own. This suggests we subconsciously look for a partner that will help us to produce strong, healthy, disease resistant babies. Who knew?

Your nose may be sniffing for a specific gene profile, but that doesn’t stop us being attracted to like-minded individuals. A study of 1,523 couples, looked at the similarity of individual personality traits, found that happy couples’ personalities synced up 86% of the time. And it’s not just personality traits – you’re also likely to be attracted to someone who has similar values and beliefs to you. In another study of 1,500 pairs, every single couple held similar life views, including the ones who had only just met.

Attachment

We talk about the moment of falling in love as if we have been hit by Cupid’s arrow – it is intense, overwhelming, often fast and feels fated. Love is said to be like a rollercoaster and, as we have seen, a chemical joyride. As time passes, this initial burst of feeling (chemicals) subsides into a comfortable closeness. The passionate, dopamine-drenched attraction period is replaced by a blissful chapter of attachment. Oxytocin, termed the ‘cuddle hormone,’ and vasopressin are the final two ingredients in this biological love potion. An incredibly powerful bond, as well as the ability to read each other’s eyes and body language, is all down to oxytocin. The chemical is created in abundance during physical contact with a partner, one example being hand-holding. Nature changes the game again, after all, she has to keep you interested long enough for the consequences of physical intimacy to become apparent.

They say that there is someone out there for everyone. But with 9+ billion people to search through you can be forgiven for asking whether we can predict out ‘type’ – minimise the search parameters. Some have suggested that we might be able to identify perfect partners endocrinologically, where they are defined by the pre-dominant hormone ‘managing’ us: oestrogen, testosterone, dopamine, or serotonin. From a biological standpoint, people subconsciously choose partners with physical characteristics that suggest fertility and health. Speculation from psychologists suggest that we prefer people of the same socioeconomic background and shared values – essentially those who share qualities we possess and an upbringing similar to the one we experienced. Traditional psychologists, such as Sigmund Freud, proposed that it was infantile memories that affected the selection of whom we would later love. I prefer the summary given by the character Dennis Reed (David Hyde Pierce) in the movie ‘Sleepless in Seattle’: “Annie, when you’re attracted to someone, it just means that your subconscious is attracted to their subconscious, subconsciously. So what we think of as fate is just two neuroses knowing that they are a perfect match.”

In the end, all our scientific measurements, psychoanalysis and poetic interpretations simply provide us with the tools to better understand the machinery of love. That is all well and good in the laboratory (and the marketing departments of dating apps), but, in truth, I think love is what we make it.