IF YOU FOLLOW the conversation about female relationships, it’s easy to assume that women spend all their time tearing each other down.

Last month, a study found that women who engage in “fat talk” are perceived as less appealing by other women. And a new study suggests that regardless of their own level of sexual activity, women are generally unwilling to befriend other women classified as “promiscuous” (i.e. having more than 20 sexual partners).

Meanwhile, women in most western countries suffer from lower pay and greater obstacles to obtaining high-powered positions than their male counterparts. All of which begs the question: In this climate, why does it seem like judging and competing with each other is the new way for a woman to get ahead?

It turns out, the way female friendships have evolved makes them different than cross-sex friendships. This helps explain all that ugly competition — but it also demonstrates why having a solid group of girlfriends may be more important than ever.

THE BENEFITS OF GETTING ALONG

When it comes to friendship, there’s a lot to be gained from male/female relationships (even if it’s just learning more about how to relate across the sexes). But evidence suggests that in many cases, women actually value their female friendships more. For a while now, research has suggested that women rate same-sex friendships higher for quality, intimacy, enjoyment, and nurturance. Other research suggests that woman-to-woman friendship lowers blood pressure, boosts immunity, and even promotes healing. Why the big payoff?

According to researchers from the Michegan Institute of Infant Health looking at how women protect their offspring, the benefits of female friendship may go back to the days of the cavewomen (and men). Back then, when humans were still prey to a number of scary animals, we developed a response to threats that’s commonly known as “fight or flight.” For the most part, scientists have assumed this response was universal. But a newer theory suggests that women developed a separate mechanism, called “tend-and-befriend,” that’s all about women working together instead of fighting or, er, “flighting” their predators.

Tend-and-befriend is a biological theory that argues because women took charge of protecting humanity’s offspring, it wasn’t always possible to fight back or run away. While male relationships could provide defense from outside threats, other women were more likely to protect each other from threats by their male peers, such as rape and abuse. Women learned to rely on each other for aid and protection. Women who were better able to band together had better chances at survival. This bonding had something to do with oxytocin, a hormone released when people bond or show affection to one another. Today, we still get the same hormonal reward when we form strong support networks.

The feel-good hormone oxytocin has been called the “cuddle hormone.” Both men and women get a surge of it when spending time with loved ones, resulting in decreased anxiety and feelings of intimacy. However, Oxytocin’s effects may not be the same across the sexes. The bonding power of oxytocin may be reduced in men. Oxytocin release in men is better researched for its role in fostering monogamy.

For women, oxytocin promotes stress reduction and relaxation, has antianxiety and antidepressant effects, and increases social intelligence, trust, and generosity. While these feel-good effects can also arise from intimate male-female relationships, researchers believe women can reap the benefits of oxytocin simply by spending some quality time with the girls.

Female friendships sound great, but how do you explain why women everywhere can so easily put eachother down?

WHY WOMEN SOMETIMES COMPETE

Let’s get back to that study on promiscuity which found that college women who slept with higher numbers of partners were stigmatised and “slut-shamed” by both men and women (even women with a similar sexual history). If women are preprogrammed to benefit from working together, shouldn’t we befriend women who are making similar life choices?

Not necessarily. A recent look at the benefits of oxytocin reveals that, while the hormone can amp up trust, it can also work the opposite way — causing higher levels of mistrust towards those individuals whom we perceive as threats to our wellbeing [1].

Our brains’ decisions to trust or mistrust someone are affected by our biological “friendship expectations” — i.e. qualities we look for in friends that will benefit us in some way. Researchers have found that men and women report different criteria for choosing new friends: In general, women have significantly higher expectations for trust, loyalty, commitment, genuineness, and acceptance (while factors such as common interests, status, power, and physical appearance hold approximately equal value to to all genders). When we detect a behavior that goes against those values, that’s when mistrust happens.

When it comes to judging so-called “promiscuous” women, it’s likely that evolutionary and sociological factors play a role. Evolutionarily, it makes sense to distance yourself from someone who could steal your partner. Sociologically, most of us are programmed with a stigma against “slutty” behavior, particularly when it comes to female sexuality. It’s therefore easy to imagine that associating with “slutty” women will damage a woman’s reputation. Other women might even feel threatened by “promiscuous” peers if they feel there’s a scarcity of partners.

HELP A GIRL OUT — WHY IT MATTERS

Women expect a lot from their friendships with other women, but the benefits of that oxytocin high are just one of the reasons we should be careful how we relate. And while more research on same-sex frienships is definitely needed, what research does exist provides strong evidence that women benefit from having a network of supportive women.

Whether it’s a concern about others associating us with promiscuity, fear that there’s only one seat in the boardroom or one spot on the ballot, or the anxiety that only the skinniest, most beautiful women will wind up in the happiest relationships, it’s understandable why some many women feel the need put down their peers. But an understanding of the evolutionary and cultural reasons behind behaviors like slut-shaming or fat talk does not excuse them. Instead, that understanding provides us with the tools to better relate to each other, a reason to embrace healthy female friendships, and a jumping-off point to change the dialogue among and about women.

Do you think having female friends makes you a healthier person? Let us know in the comments.

Why do I turn red during exercise? >

Hug it out >

MYO armband turns every arm gesture into a virtual command >