It can be argued that we’re missing out on experiencing everything that love has to offer because our field of view is too narrow. Picture: 123RF/CIENPIES
It can be argued that we’re missing out on experiencing everything that love has to offer because our field of view is too narrow. Picture: 123RF/CIENPIES

As an evolutionary anthropologist, I have wrestled with the question “What is love?” for more than a decade. At first glance, the answer is straightforward. After all, my many research subjects all have their own answers to share. And herein lies the fundamental problem for someone who would like to find a nice straightforward answer: love is complicated.

This is at once hugely frustrating and immensely pleasing because this complexity, this unknowable aspect of love, motivates us to create great art and to repeatedly embark on the exhilarating journey that is love, despite the end point being the possibility of great pain and rejection.

And what makes human love even more awe-inspiring is that we get to experience it in so many ways. I began my research life rather predictably with a consideration of romantic love but, as I started to explore the love lives of my subjects more broadly, it became clear that, yes, there might be lovers, parents, children but there might also be a god or gods, pets, celebrities and even holograms. We are capable of loving so many beings both human and non-human and in physical and nonphysical form. When you understand how important love is to our very existence, you realise how immensely lucky we are. Love has got our back.

In many cultures, this full spectrum of love is fully embraced; as an anthropologist, you get used to being welcomed as one of the family you’re observing, kin name and all. But in the West we’re missing out on experiencing everything that love has to offer because our field of view is too narrow. As a consequence we’re in danger not only of limiting the fullness of our life experience but endangering our health. This blinkered view is a result of our tendency to conceive of a hierarchy of love. The top position is occupied by parental love with dad regularly relegated to assistant parent, whether he likes it or not; parental love is usually embodied in the love between mother and child. Running a close second is romantic love, with an overwhelming focus on finding your “soul mate”. Fail at this and you supposedly live only half a life. After that, we have the immediate family — siblings, parents, grandparents — and maybe even the extended family.

When you understand how important love is to our very existence, you realise how immensely lucky we are. Love has got our back.

After all these, the next category comes a rather distant fourth — our friends. It is fair to say that, when considering love, we can neglect our friendships. Indeed, in carrying out interviews for my next book, I found that those based in the UK or the US were often very happy to quickly declare their love for their cat or dog, but ask them whether they loved their friends and many had to pause and think.

This dismissal is based on a misunderstanding of how foundational friends are as members of our social network — they are its largest group — and how they hold the key to our health and survival. My work has shown that our friendships can provide a level of understanding and emotional intimacy that can eclipse any we might experience with a lover. Indeed, friends are often the most reliable source of an interpersonal ease, allowing us to be our true selves, something that we’d do well to embrace in this 24/7 social media world where “curating” your image can be a full-time job.

More than two decades of research into the nature of human social networks, including studies carried out within my group at the University of Oxford, has led us to two important and robustly evidenced conclusions. The first is that, regardless of age, personality, gender, ethnic background or any number of possible individual differences, we all interact with the members of this network in a broadly similar way. This is the magic number of 150, Dunbar’s number (named after my colleague, the evolutionary psychologist Robin Dunbar who discovered it), and it reflects that, on average, the maximum size of an individual’s social network is stable at 150.

But not all is equal in the 150 club. Some people are allowed to get closer to us, and take up more of our time, than others, and it’s particularly within the two innermost layers of this network that we find our closest relationships, including our main friends. At the very core of our network sit our central support clique, the four or five people to whom we’re emotionally closest and to whom we will dedicate 40% of our time. Many of us tend to have daily contact with this core, including our romantic partner, our children, maybe our parents or a best friend. Next we have the 10 or so people known as our sympathy group. These are our go-to people for a break away from the immediate family or a good night out, and we interact with them weekly. These are our close friends and maybe the occasional sibling or cousin. Together, the 15 people who make up our central support clique and our sympathy group get 60% of our time. The remaining 40% of time is spread thinly over the remaining 135 people who constitute the rest of our active network, and the further out you are, the less of this slim sliver of time you will receive.

There’s a powerful relationship between the characteristics of your social network and your mental and physical health, your longevity and your general life satisfaction. Way back in the knife-edge environments of our evolutionary past, having a strong social network was essential to survival, and there are still areas of the world today where having the help and support of others is the difference between life and death.

We think that what’s important for a healthy life is exercise, a balanced diet, not smoking and maintaining a healthy weight. But a seminal study carried out in 2010 by the psychologist Julianne Holt-Lunstad at Brigham Young University in Utah and her colleagues would beg to differ. Holt-Lunstad collected together the data from 148 studies that had explored rates of mortality after chronic illness — cancer, cardiovascular disease and renal failure being the most prominent — and aspects of an individual’s social network. For some studies, this was the size of their network, their actual or perceived access to social support, their social isolation or the extent to which they were integrated into their network.

Holt-Lunstad concluded that being within a supportive social network reduced the risk of mortality by 50%. That places it on a par with quitting smoking, and of more influence than maintaining a healthy BMI measure. Since Holt-Lunstad and colleagues reported their findings, study after study has reinforced this conclusion, to the extent that we can now argue that the nature of your social network, and the strength and health of the relationships within it, is the biggest single factor influencing your health, happiness and longevity. They are your survival.

But what has all this got to do with your friendships? Why does neglecting your friends place you at considerable risk of ill health and guarantee that your life will be much less joyous and satisfying? Because for a big number of people — a number that’s growing year on year — their friends fulfil the role of a romantic partner, a child and even a whole family. Their friends are those key 15 people they see and rely on most. As a consequence, they are the survival-critical relationships that will have a profound influence on their health, happiness and longevity.

On average, the maximum size of an individual’s social network is stable at 150. Picture: 123RF/NEXUSPLEXUS
On average, the maximum size of an individual’s social network is stable at 150. Picture: 123RF/NEXUSPLEXUS 

Data from the 2015 US census has predicted that 6% of the adult population of Americans will remain single their entire lives. And the number of never-married singletons in their 40s has doubled in the UK between 2002 and 2018. Globally, we’re experiencing a big downturn in the birth rate. In Japan, deaths can outstrip births by nearly 500,000 a year, meaning that by 2050 the population might have shrunk by 30-million people.

Many people will remain childless. In the US, the rate of births in women between the ages of 20 and 29 dropped a 15% in the five years between 2007 and 2012, with this trend not limited to any one ethnic group. In some cases these declines are due to women choosing to have children later in life or, in Japan’s case, a fall in the number of women of reproductive age in a shrinking population. But, in many cases, women, particularly those of the millennial generation, are choosing to not have children. Instead, they’re deciding to focus their energies on building a good career and directing their caring skills to the community. For these people, their central support clique isn’t populated by a lover or children. It’s populated by their friends.

Perhaps as a reflection of our perception that friends are unimportant, compared with the attachment between lovers or a parent and child, research on the power of the friends’ attachment is still only in its early days. However, in her 2017 study of female singles, Claudia Brumbaugh, a psychologist in New York, found that best friends played a crucial role for them, both because of the freedom to choose them, and because of the close similarity to them. Brumbaugh found that, when it comes to choosing our friends, there’s none of the familial obligation or cultural pressure that can influence our choice of lover or our commitment to our family.

The nature of your social network ... is the biggest single factor influencing your health, happiness and longevity.

With such unfettered choice, what draws us to the people who ultimately become our friends? One of the first studies I carried out at Oxford was an analysis of how heterosexual people chose their romantic partners and their best friends. I asked the participants to what extent they shared a range of attributes with their lover and their best friend, including levels of physical attractiveness, creativity, intelligence, education, sense of humour, outgoingness and optimism. What was important in each case? I was trying to understand whether there was a “friendship market” much like a “dating market”. Since our friends contribute so much to our chance of survival, shouldn’t we be taking some care in choosing them?

What I found surprised me and challenged the idea that our friends can never be as close to us as our lovers. For many heterosexual women, their same-sex best friend was someone with whom they shared more emotional intimacy than with their male lover. For many heterosexual men, their same-sex best friend represented ease of interaction and a sense of humour,  someone you could truly relax with. Further, both sexes had more in common with their best friend — that is, they were more similar to them in terms of education, interests, and so on — than with their lover. These results perhaps point to the inherent tension that exists at the centre of all heterosexual romantic relationships.

Evidence that our friends often know us as well as we know ourselves comes from a 2019 study in which people were asked to consider their own personality, and the personalities of 10 friends, while inside a brain scanner. The psychologists Robert Chavez and Dylan Wagner found that when an individual, let’s call her Sarah, reflected on her own personality, her brainscan pattern matched the pattern seen in the scans of her 10 friends while thinking about Sarah’s personality, but not when they thought about their other friends’ personalities.

According to a 2018 study, the signals seen in the brains of friends were more similar than those between people who were not as close. Picture: 123RF/PLAVSHA
According to a 2018 study, the signals seen in the brains of friends were more similar than those between people who were not as close. Picture: 123RF/PLAVSHA 

And the extent of these similarities between friends can stretch beyond a shared love for French avant-garde films or a shared school experience to the fundamental way in which we make sense of our world. In 2018 the researchers Carolyn Parkinson, Adam Kleinbaum and Thalia Wheatley recruited 279 students, the entire cohort from one year of a graduate programme. They asked them to complete a questionnaire listing everyone in the programme they deemed to be a friend. The researchers then set about creating a social network for the class, illustrating every link between the students. Their prediction was that the closer two people were to each other in the network, indicating a stronger bond, the more similar their neural responses would be. A subset of 42 students was used for a scanning study. Once in the scanner, everyone watched the same set of videos in the same order. And the results confirmed the researchers’ hunch: similarities between friends extended way beyond hobbies, ethnicity, age or sex. The signals seen in the brains of friends — both in the unconscious and conscious brain — were more similar than those between people who were more distant in the network. They were also able to predict just how close two people were in the network simply by comparing scans. Now that is a concrete finding.

The term “chosen family” was first coined in the US during the ’70s and ’80s to describe the networks of friends that provided emotional support and nurture to those who had been rejected by their own family or who were excluded from legally sanctioned methods of creating a family such as marriage or parenthood. In the vast majority of instances, these were gay men and women who had been excluded by their culture and/or disowned by their biological family, and whose need for support was made all the more urgent by the arrival of HIV within their communities.

These families were bound by a shared identity rather than shared blood — they were fictive kin. While those who pioneered this new form of “friend” family in the 1970s have now grown old within the bosom of their chosen family, recent work among younger communities in the US has shown that chosen families are as important to the lives and as vital to the security and development of young people as they’ve always been, particularly when it comes to one of the trickier aspects of growing up — exploring your sexuality.

In 2013, the Illinois Caucus for Adolescent Health (ICAH) carried out a study exploring the role of chosen and given family in discussions with adolescents about sexual identity, health and rights. They used individual interviews, online surveys and focus groups to explore the experiences of nearly 500 adolescents as they navigated this at times rocky and confusing stage of their development. The results showed that, while there was a role for both family types, the chosen family was the first port of call when discussing these potentially tricky topics.

In fact, of those interviewed, 80.7% reported that they had formed a chosen family. When it came to discussing sex and sexuality, 73.4% of young people spoke to their chosen family compared with 52.8% who spoke to their given family. But when it came to how comfortable they felt while doing this, 63.2% were more comfortable talking to their chosen family as opposed to only 9.7% who felt comfortable speaking to their given family. Because members of Generation Z (that is, those born between the mid-1990s and early 2010s) explore their gender and sexuality more freely than any previous generation, it’s clear that the love and understanding found in a chosen family is as vital as it’s always been.

As our Western world becomes slowly more tolerant, the options for creating your family become broader. While the statistics seem to point to a world where fewer of us choose to find a romantic big other, this doesn’t mean that we must spend our lives alone or miss the opportunity to become parents. I spend a lot of time exploring the changing world of parenting, and it’s fair to say that today’s reality is far from the Victorian nuclear ideal.

It’s clear that, in opposition to the accepted order of things, for many of us, it’s our friendships that need to be at the top of our love hierarchy if we want to live long and happy lives. Friends can be our sources of intimacy and non-judgemental support, they can be our life’s companions, they can be our family and our co-parent. Put bluntly, they’re our survival. But this means that we must decide to nurture and invest in them to benefit from their many rewards. Our unique ability to love many beings in many ways means that we all have the opportunity for love in our lives. We just have to lift our eyes to the horizon and broaden our perspective to see all the love that is on offer. And for many of us that will mean celebrating, treasuring and reasserting the love we have for our friends.

• Anna Machin is an evolutionary anthropologist, writer and broadcaster whose work has appeared in the New Scientist and The Guardian, among other publications. She is the author of The Life of Dad: The Making of the Modern Father (2018) and Why We Love: The New Science Behind our Closest Relationships (forthcoming, 2022). 

• To read more about mental health, visit Psyche, a digital magazine from Aeon that illuminates the human condition through psychology, philosophical understanding and the arts.

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