Dr Anna Machin | University of Oxford
Family silhouetted by sunset
Family silhouetted by sunset
Credit: Shutterstock / Sean von Tonder

Dr Anna Machin

"Love is love and its neurochemical processes apply consistently in all ages. You can fall in love as profoundly when you’re 21 as when you’re 55."

Dr Anna Machin is an evolutionary anthropologist from the Department of Experimental Psychology, whose research is based on the neurobiology and psychology of human relationships, particularly romantic and parent-child relationships. She is keen to inform us about how love works and to help us with our approach to finding and maintaining a partner. To that end, she has collaborated with BBC Earth and appeared on a Channel 4 show to make matches on a scientific basis. Anna also works with charities to raise awareness of unhealthy parent-child relationships and how they can affect relationships in adulthood. She argues that our bodies encourage us to seek certain partners and then maintain them because of genes and neurochemistry. I am particularly curious to find out how time affects these mechanisms that are involved when we love.

It is evident that we live in a world in which divorce rates are high, short-term love is popular and dating is greatly shaped by online dating sites, many of which are dedicated to finding people just for fast encounters. However, Anna’s research is based on long-term love, because she is interested in how "long-term relationships are what actually underpin human behaviour, culture and reproduction. Love only comes in the longer term." She argues that love is based on reproduction, because it is what evolution needs. "Romantic love and parent-infant relationships need to last in order to succeed," she explains. "There is a connection between the two, because we have long-term relationships so that we can raise children well, from an evolutionary viewpoint, considering that human babies are so helpless and dependent, needing a long time to develop. Lasting love is there so that children grow healthily, as human parents must stay together longer and bond with their child more than animals do." So Anna is sceptical of online dating and the importance of love with no strings attached. She says: "This period we live in, with more focus on short-term relationships, is still a really short phase in our history, from an evolutionary perspective, so I would argue that our basis of long-term relationships will continue, without undergoing much change in our time. When I started my research on this topic, a lot of these dating platforms didn’t even exist!"

Do you think the modern ‘dating game’ is a problem, then? How can it improve?

These social media platforms, like Tinder, have had a detrimental effect on relationships, but this is not necessarily a problem to be solved. These platforms are a tool to be used, although we are not quite sure of how to use them to our benefit yet. At the moment, we are a bit overwhelmed, like kids in a sweet shop, with so many possibilities. Suddenly, the dating scene has gone from meeting some people in your town or region to easily meeting hundreds of thousands of people out there through the Internet or travelling, all around the world. We still need to adapt to this properly. This is great, because it increases our options, and it is even better for somebody who has trouble finding a partner, who will now have more chances in an easier way. On the other hand, the problem is that we have a ‘paradox of choice’: there are so many choices that it’s hard to settle for somebody in particular and there is always the temptation of swiping one more time to see if you can get someone better. Nowadays, a lot of people never pair up and are always looking for the next best thing, which is not good for us individually and for our society.

Ultimately, we need long-term relationships, because of how we have evolved, and what is important for long-term love is physical contact, not online interaction. We will eventually learn how to use these dating platforms better, though. I already notice a slight reaction, with some dating sites focusing on face-to-face contact again, making people meet each other immediately. I predict that there will soon be another revolution in the dating scene to bring back the contact, so there will be improvements.

We produce a major complex of neurochemicals that are released when we interact with each other, face-to-face. It does not work with online communication. The only way to form a long-term relationship is regular physical contact: laughing with that person, touching that person… Relationships work due to these neurochemicals: oxytocin, dopamine, and endorphins. Our bodies have evolved to crave them and if you don’t get them it is detrimental, particularly for your mental health!

So we need love to stay healthy? What kind of love?

Yes! It does not need to be sexual love, it can occur with different kinds of social contact: with friends, for example, or with your child or your family. All these kinds of physical contact produce those essential neurochemicals. The same neurochemicals underpin long-term interactions with lovers, children, friends… What varies is the intensity: the response will be stronger with your child than with your friend, even your best friend, because parent-child relationships are based on survival for evolutionary reasons and therefore they need to be incredibly deep. We have similar ‘attachment relationships’ with our romantic partners and our children, but it is debatable whether a friendship fits into that category. Others may claim that you can also have the same attachment with friends, but I would say it’s probably not the case.

We can trace this back to primates, our closest animal relatives. When they groom each other, they produce similar neurochemicals like endorphins and this is their social glue. However, in primate groups, long-term relationships are friendships or alliances rather than love, because it is more helpful for them and they do not need to be so invested in sexual relationships for their offspring’s sake or stay so long with them as humans do.

You draw connections between parenting and romance. Does parent-child interaction influence behaviour towards love later in life, staying with us over time?

I wouldn’t argue it like Freud did, but yes, it does. The incredible Dr Ruth Feldman from Israel has investigated this and discovered the links, which are based on bio-behavioural synchrony. This is how it works: if a parent-child relationship is healthy and goes well, the oxytocin levels of the child will become the same as the parent’s oxytocin levels (a synchrony) and that occurs when the child’s brain is developing, when neurones are formed. Therefore, the child will have the right neurochemical processes and the structures aimed at responding to social relationships in the child’s brain will develop correctly, leading the child to respond well to social and romantic relationships later in life. In deficient parent-child relationships, those areas of the child’s brain will be dysfunctional and when the person is older, s/he will be more likely to have unhealthy relationships, not getting the right neurochemical processes from them. These are life-long issues and that problem can be passed on across generations.

What differences are there between short-term love (for example, a crush) and long-term love? How do relationships keep going for a long time?

A crush is basically lust, a shallow relationship. Lust can be a stage of love, which might lead to more in the long run. This stage is underpinned by short-term neurochemicals such as oxytocin, which then interacts with dopamine. The challenge for evolution has been to create the chemical that maintains long-term affection for years.

Some people are genetically predisposed to seek firm long-term relationships and others are more prone to conflict in love. There are no right or wrong genes

Research leads us to think that this is a neurochemical called beta-endorphin, which is a natural opiate, like heroin, so it is addictive. Generally, it is released in the body as a natural painkiller, when you hurt yourself, but also during physical interactions. When we touch, hug or interact people, we get a hit of beta-endorphins! I would argue that this is the chemical that makes long-term relationships work, because when we interact with our partners we have a hit that makes us feel amazing, but when we get away from them we suffer withdrawal effects, which drive us to go back to that person constantly. So long-term love is addictive. However, all relationships need maintenance, so when there is not enough effort after some time or when there is inevitably less contact, less laughing and touching each other due to routine, the endorphins remain but the hits decrease. Endorphins will remain addictive anyway, we can’t reach tolerance to them.

Oxytocin gets all the headlines and it’s easy to test, but it is more difficult to test beta-endorphin. The only ways we can categorically prove that it’s released are by a radioactive PET scan or by a spinal tap, taking out spinal fluid.

How does love vary in different ages, if at all? Is there an ideal time for love?

Not really, love is love and its neurochemical processes apply consistently in all ages. You can fall in love as profoundly when you’re 21 as when you’re 55, because the neurochemicals don’t act differently. People go through the same psychological stages of love, from lust to a more companionate love. I would say that the only difference is the experience that you gain as you get older. There is no specific ideal time, because endorphins are always there and don’t fluctuate like sex does.

You participated in the TV show Married at First Sight, in which you made ideal romantic matches and based your choices partly on genetic profiles. How far do genes determine attraction or the type of lover we may seek? How effective is it to match people in this way?

It is flexible, although genetic research is in its early stages. The degree of symmetry in your body reflects to what extent you have ‘strong genes’ (such as physiological health and a strong immune system), because in the womb there are chemical and environmental challenges that can knock your genes off their program to make you bilaterallysymmetrical if they are not strong enough. So we find symmetry attractive because it displays stronger genes that resisted these challenges and you would want such better set of genes for your offspring. Also, human mating is assortative, which means we seek people similar to ourselves: it’s rare to see a highly symmetrical person with a highly asymmetrical person. But there is no wrong degree of symmetry. In the show, we focused on facial symmetry for matchmaking because you will work better with someone of similar symmetry.

We also started to discover that some genes, particularly those linked to the oxytocin receptor gene, seem to influence how people behave in relationships. Some people are genetically predisposed to seek firm long-term relationships and others are more prone to conflict in love. It is not deterministic and it depends on people’s environment too. In the show, I sought balances and avoided putting two people with the conflictive genes together, but there are no right or wrong genes.

The problem with TV is that people may not realise that this is fallible. There is no formula, but the program’s aim was to give people a better chance in love. Dating sites should acknowledge evolutionary issues like these, because the information they use is too narrow. It is a matter of widening the scope of information to provide better choices.

Overall, to what extent is love a biological or cultural phenomenon? What is its essence?

It is a mix. Humans are complex creatures, so explanations for our behaviour occur at different levels. At the most basic level, love is just a neurochemical reaction in our brains, but we cover our behaviour with many layers of culture. However, the neurochemistry is what underlies love in all cultures whilst cultural approaches to love may change and there are cultural differences depending on political systems, place, societies’ legacies of romantic poetry, etc. There are even societies that reject cultural concepts of romance, but the neurochemistry remains. Although it isn’t my specialism, homosexuality is an example of how a neurochemical process happens despite the cultural pressure against it in many societies, because biological processes are the roots of our behaviour.

Common sense would lead us to think that love changes over time, but Anna has showed how in fact its purely biological processes stay the same. With this revelation in mind, maybe I can find out more about how attraction works beyond all our social preconceptions in the next interview with zoologist Tristram Wyatt, who has researched pheromones, part of another interesting mix between cultural myth and biological reality.