The ‘biological bribery’ that explains why humans fall in love
Is it companionship, procreation or something more? Dr Anna Machin reveals what makes us so willing to become targets for Cupid’s arrow.
At the most basic level, love is about survival – of the individual and the species. Humans are highly cooperative; we have to cooperate to subsist, to gain knowledge and to raise our highly dependent offspring. But cooperation isn’t easy. In an ideal world we’d live in blissful solitude doing what we wanted when we wanted and not having to consider the needs of, or the threats from, others.
Group living means that we have to compete for resources, coordinate our movements, exist within a hierarchy and make sure we keep an eye out for those who might lie, cheat and steal. So, what has evolution come up with to ensure we start and then invest in these survival-critical relationships despite their costs? Love.
Is love just chemicals?
Love evolved to bribe us to commence and maintain those relationships – with lovers, children, family and friends – which we require simply to stay alive and perpetuate our genes. And this biological bribery comes in the form of a set of four neurochemicals that underpin attraction and love: oxytocin, dopamine, serotonin and beta-endorphin.
Oxytocin is important during attraction as it lowers your inhibitions to starting new relationships by quietening the amygdala, the fear centre of your brain, meaning that you’re confident when approaching a new acquaintance.
Dopamine is always released at the same time as oxytocin. It’s your body’s reward chemical and is released whenever you do something you enjoy. In this case it rewards you for your confidence, as well as working with oxytocin to make your brain more plastic – enabling you to learn and memorise new facts about this new person – and, as the hormone of vigour, motivating you to get out of your chair and make the approach.
These chemicals act mainly in the limbic area of the brain, its unconscious core. This is because attraction, or lust, is initially a purely instinctive and unconscious sensation. Lowered serotonin unleashes the obsessive element of love. Unlike the other chemicals, serotonin drops at the start of a relationship, which is why your mind tends to be overwhelmed with thoughts about your new love.
And finally, we have beta-endorphin. This is the hormone of long-term love. Humans can be in relationships for decades and oxytocin, in particular, is not powerful enough to underpin love in the long-term. Further, oxytocin is mostly released in significant amounts only in situations related to sexual and reproductive love meaning it’s not capable of underpinning friendship – a key, survival-critical human bond.
But beta-endorphin can and it works because it’s an opiate, like heroin or morphine. And as with heroin, it’s addictive. It works because we become addicted to those we love as the source of our opiate high and, when we’re apart, we go cold turkey, motivating us to return to them for another euphoric hit.
Because beta-endorphin underpins love, rather than lust, both the unconscious and conscious areas of our brain (respectively the limbic area and cortex) are recruited, meaning that humans can experience love as an instinctive drive or emotion involving lust, anger or delight, but also as a conscious process involving reflection, trust, empathy, attention and planning.
Anna is an evolutionary anthropologist, writer and broadcaster.