In an episode of the satirical comedy The Great, the reign of the reason-and-science-loving Russian empress Catherine nearly collapses when her husband Peter, the deposed emperor, storms into her private quarters, determined to imprison her. But seeing her tearful and in despair, he forgets his vindictiveness and hugs her. Later, he tells her, “I wanted your happiness more than my own.” “Wow,” she responds. “Indeed,” Peter says. “Love has done a strange thing to me. I wonder if you cut a man who has loved fiercely, you will see a different-shaped heart from a man who has not?”
Of course, no literal imprint of fierce love would be found in the heart if scientists went looking. But it’s safe to say that Peter was on to something. Love, scientists have shown, leaves noticeable and widespread traces of its impact on us. “Love is so important,” says evolutionary anthropologist Anna Machin, “that evolution has seen fit to engage every mechanism in your body to make sure you’re as close and bonded as you can be.”
Machin, who studies the genetics and neurochemistry of love—and has collaborated with the renowned Oxford anthropologist Robin Dunbar, of “Dunbar’s number”—is the author of a new book, Why We Love: The New Science Behind Our Closest Relationships. In a recent interview with Nautilus, she says she tackles the whole spectrum of loving relationships from a variety of scientific perspectives to explain the nature of love. “If you’re a neuroscientist, you give one particular answer. If you’re a psychologist, give another one,” she said. “As an anthropologist—it’s a bit of a magpie profession—I gather all that together.” Machin’s responses to my questions were articulate and energetic, despite how far into the evening it was for her in England.
Why do you call love a form of bribery?
The reason love evolved was to motivate and reward us for taking part in relationships, critical to our survival. That goes for our reproductive partners, children, and extending to our friends. Humans are highly cooperative because we have to be. A species will be solitary unless it absolutely has to cooperate with somebody else. And that’s fine, except it’s incredibly stressful. You have to spend a hell of a lot of time monitoring everybody else’s behavior, making sure you’re spotting those people who are trying to cheat you or steal from you.
And the way evolution made sure we cooperate was to come up with chemical bribery. At the basis of love are four neurochemicals. Each has a different role but together they motivate us or to give us confidence to go into social relationships. Ultimately, we get addicted to those chemicals. We get this hit of joy, of euphoria, of reward when we interact with the people important to our survival. It’s biological bribery. It’s like if I give my kids a sweet because they’ve done something good, which is bad parenting, but it works.
You also say love is about control. Why’s that?
Because the only point of evolution is to pass genes down. This form of bribery is controlling us to make sure we do that. It’s a benign control. For most people, most of the time, the experience is lovely and warming and beneficial in terms of health. Unfortunately, our biology to seek love, crave love, find love, keep love, is a weakness. That visceral need can be exploited, it can be used to make us do things we don’t necessarily want to do. And that’s the cost of love. It can be used to manipulate or abuse or coerce us. That’s what separates us from the animals. Animals don’t use love to manipulate others. We do.
You say it’s scary that a baseline level of oxytocin, one of the neurochemicals of love, can predict whether a couple will be together six months later. Why’s that scary?
When it comes to a relationship, it’s a little bit scary to know that part of that relationship is written in the stars before you even started. That’s because people with higher levels of oxytocin generally are more open to relationships, they are more committed to wanting to work toward a relationship. In fact, there are many things that go into whether a relationship will last—oxytocin levels, genetics, upbringing, your attachment profile, the support of your family. So it’s the private me talking, saying, “Oh my God, you meet someone, you think they’re wonderful, but the relationship is partly already written.”
We get this hit of joy, of euphoria, of reward when we interact with the people important to our survival.
Is love blind?
Yes. What happens when you fall in love for the first time is the activation of various areas of the limbic system and the neocortex. But we also see deactivations. These deactivations occur mainly in the brain area linked to “mentalizing.” Mentalizing is the ability to tell someone’s intentions, and you need to be good at mentalizing to spot a liar or a cheat. To be able to tell if somebody is lying, you need to be good at understanding what their motivation is. But what happens when you fall in love for the first time is that bit shuts down. It just decides it’s not going to work anymore. For that reason, your friends can see this person is not necessarily good for you, that maybe they’re going to cheat on you or they’re lying to you, but you cannot see it.
Why would being blind in love have evolved?
It’s interesting. Why would that have evolved? Why would that be something that was retained? Is it something to do with the same way that oxytocin lowers your inhibitions? Maybe it’s to remove some of the hurdles that you might place in your own way when you’re going to try and start a relationship. If you were constantly paranoid that everybody’s going to cheat on you or steal from you or lie to you, the species wouldn’t get very far. So maybe we have to remove that ability so that we have confidence and enough belief in the person that we fall in love with that we will carry on doing this. We see the same deactivation occurring when people listen to a charismatic religious leader.
Why do we fall in love with one person and not another? Or maybe I should ask, Why do we have lust for one person and not another?
That’s very much a sensory input. Lust is an unconscious emotion. It takes place entirely in the limbic area of your brain. It happens within the first nanoseconds of you seeing somebody across a room. You’re going to use all your senses. They’re going to tell you things about that person’s health, their ability to protect, to provide, about the strength of their genes, particularly if you’re looking at sort of asymmetry within the face. You’ll listen to the tone of voice and what they say. And what they say is a good indication of cognitive ability or flexibility of intellect, or sense of humor.
Initially, you take in this information unconsciously. The algorithm in your head will decide, OK, this is somebody for you or this isn’t somebody for you. We all have a biological market value on our head, which is linked to the likelihood of reproductive success. The more likely you are to be reproductively successful, the more wealthy you are in terms of your biological market value. That classic thing when you see someone across the room and you think either, “Oh my God, they’re completely out of my league.” That’s basically what your brain’s thinking or, “I can do so much better.” That’s part of the calculation. If you get a tick from your algorithm, then oxytocin and dopamine are released and off you go, and you fill that chemical sort of job, that lustful feeling, that chemistry that develops between two people. The conscious brain kicks in pretty quickly after that, but the first moments are completely unconscious.
Why do you say the biology of love can sound non-feminist?
The reason for that is I often get called out. I do a lot of public speaking and I explain to people the rules of mate choice as biology sees them. But a lot of women, in particular, find it hard to accept that they are still looking for a protector and a provider. I try to explain that even though they are now capable of being independent, financially independent, they’re still looking for that in the man. These mate-choice rules are evolutionarily incredibly ancient. Whenever we see mate choice in any species, this is what we see. One reason why some women are in a position where they’re financially comfortable, and don’t need a man for that, is because they live in a culture where there’s a certain amount of gender equality. That has come about partly from feminism. But feminism hasn’t touched evolution, partly because it’s very recent. Women have only been able to control their contraception, for example, for about the last 70 years. That’s nothing in evolutionary time. Something as deep-seated as mate choice only changes in human behavior when it’s pretty much universal among the species, and there is not equality in a vast number of countries in the world, so it’s not going to touch it.
Animals don’t use love to manipulate others. We do.
What do you mean when you write that “cross-sex cooperation is cognitively the costliest of all cooperation?”
This is something that people find difficult to accept. You always get cooperation within a sex before you get cooperation between the sexes. You’re only driven to cooperate with the opposite sex when you’ve exhausted your own. The reason is we’re trading similar currencies in our own sex.
When we look at the environment in which we evolved, the biggie was childcare. We have these dependent babies. To be able to function, you need help with those children. And women would turn to their female kin first to do that. Cooperation is all about reciprocity. We want to make sure the balance sheet is even. You don’t want to be the one always doing all the helping and never getting anything back. From a survival point of view, that’s not a good thing to do.
With men, you tend to be trading things like alliance, support, help in fights. When you get men and women cooperating, particularly in the human evolutionary line, you are trading those different things. Women still want childcare. I would like you to help me raise our children, but the man is there because he basically wants to have sex and produce some more children with her. You’re trading sex for childcare.
So those are two different currencies. Your brain is having to do a currency calculation. And when we look at the way the brain has evolved, we see the development of cognitive architecture that enables you to start doing those more complex calculations. So cross-sex cooperation is so much harder at the fundamental level than cooperating within your sex.
You say there’s a difference between how mothers and fathers form attachment to their kids. How so?
Attachment is a deep, psychological bond between two people. A mother’s attachment is based purely on nurture. The strength of that attachment will be based upon the sensitive and positive way she nurtures that child. For a father, nurture is important, but there’s an added element that comes from the cortical area of the brain. That’s the bit saying, “OK, I’m going to push your developmental boundaries. I’m going to make you more resilient. I’m going to push you into the world beyond the family.” What joins all fathers around the world is they have this role in scaffolding the child’s entry into the social world. That’s the underpinning of what they’re involved in developmentally.
People can sometimes find that difficult because they’re like, “Well, those are just culturally gendered roles.” Yes, you can argue that, but it also has an evolutionary explanation, which is the fact that evolution doesn’t do redundancy. It doesn’t cause two individuals who have input into something to have the same role if that’s not required because that’s just a waste of energy. Bear in mind that human children take a huge amount of emotional, cognitive, and practical input to raise. So it’s important that the parents fit together well and give that developmental environment.
What does your research say about parenting in a non-traditional family?
What happens is we see changes in the brains of a single parent or a parent in a same-sex couple. The human brain is incredibly plastic. All parents have the ability to nurture, to challenge, to build resilience. We see changes that enable the brain in a single individual to behave in ways like a mom or dad. If we look at say, the Aka people in the Congo, where the fathers spend about 60 percent of their time in physical contact with their children, you will see a different way of parenting. As with everything, some parenting is biological, and some is environmental and contextual. What we found universally with men is they have a role in building resilience in pushing their child into the world, but they do that in a culturally specific way. It depends on the environmental context of what that world is.
You’re only driven to cooperate with the opposite sex when you’ve exhausted your own.
How does our upbringing as kids affect our love lives?
Let’s say you had a secure attachment to your parents when you’re a child. That means you had sensitive parenting, they were aware of your emotional and physical needs, and met those needs. You were secure, you did not suffer anxiety, you did not suffer abandonment. That’s bathing your brain in oxytocin and dopamine and beta endorphin, and you’re producing low levels of cortisol, you’re producing this highly efficient brain, you’re not going to see neuronal death, which is what happens with neglect. When you go forward, you’re going to have the biological underpinnings and the psychological underpinnings to be able to build good attachments, to build healthy relationships, and know when a relationship is not healthy for you, in which case you should leave.
Unfortunately, the opposite happens. We see brains bathed in a high degree of cortisol. We see active neuronal death, which means you see reductions in gray and white matter in those pro-social areas of the brain. They do not go forward with those abilities to do all that, to do the reciprocity, the trust, the empathy. The behavior they have watched, which is relationship behavior, is not good and that’s something that they will replicate going forward. But they also do not have the powerful biological underpinnings to enable them to be able to have good relationships.
You say we underestimate the love that comes from friendships. That might be starting to change. There was a widely read article in The Atlantic recently that touched on this titled, “It’s Your Friends That Break Your Heart: The older we get, the more we need our friends and the harder it is to keep them.” How does that headline strike you?
We tend to privilege romantic relationships and maybe parental relationships, but we take our friendships for granted. But they are incredibly important to you. They are the only platonic relationships you get to choose yourself. You don’t get to choose your family but you get to actively choose your friends. In fact, our research shows that you are much more similar to your friends than you are to your lover. If you’re a woman, you are more emotionally intimate with your friends than you are with your lover. If you’re a man, your friends bring this ease of being able to really be you.
So our friends provide a lot to us. And we neglect our friendships at our peril because often our friendships outlast our romantic relationships, and they are the ones that are really your stable foundation. You need them in your life for your mental health, your physical health, for your longevity, and your well-being. But I do think we underestimate them. I interview so many people for my research, and particularly when I interview British people, I’ll ask them, “Do you love your friends?” And they’ll go, “Hmmm, I don’t know whether I love them.” And then I’ll say, “Well, do you love your dog?” “Oh God, yeah! I love my dog.” And it’s just this thing that we don’t consider the fact that we could love our friends. And I think that’s maybe a peculiarly British thing that’s quite restrained that we wouldn’t admit that.
The philosopher Alain de Botton has argued that romanticism has severely distorted how people think about love and what to expect from it. What do you think of that?
I agree with him. The narrative is unhelpful. This idea of the chivalrous prince rescuing his princess from a castle. It sets up an incredibly idealistic view and very gendered view of what romantic love is, which doesn’t reflect the reality for most people. The idea that there is the one—well, we can quite clearly tell from the inputs that go into what attracts people that there’s more than one person in the world for you. Also, from an anthropological and sociological point of view, it’s a narrative that works for society because it’s a controlled narrative: We can have everybody pairing up with one other person and we set in place all these rules. We have these zero-sum ideas of love. But the idea of romantic love doesn’t reflect the reality of people’s existence, particularly with increasing singledom. The idea that romantic love is the most powerful love is unhelpful because it demotes all the other ways that you can love in your life. And none of them are weaker than romantic love, but we seem to think that they’re not as good. They’re not as important.
The narrative also doesn’t help people get out of abusive relationships. If you tell a child that love is like a fairy tale, you’ll get swept off your feet, that love lasts against all odds and will help get over any hurdle, that doesn’t help in the context of abuse. It leads to the idea that you have no control over this person that is abusing you. When you do. So it’s a really unhelpful narrative. And it’s a narrative that’s spun mostly today by commerce. You can have the perfect wedding with your soulmate. That’s the be-all-and-end-all of life. I sound cynical, but I completely agree that romantic love is not a helpful narrative.
Has becoming scientifically knowledgeable about love affected your personal relationships in any way?
It hasn’t affected it in a negative way at all. People say, “Well, it must have been because you spend your life in cold science, analyzing what love is.” I think if that’s all I did, I think it would. I think if you reduced it constantly to a set of neurochemicals or a genetic driver, I think maybe you would. But because I do it from an anthropological perspective, and spend a lot of time talking to people about their love, I just find love an amazing phenomenon. The more I study it, the more in awe I am of its complexity in the human species.
Brian Gallagher is an associate editor at Nautilus. Follow him on Twitter @bsgallagher.