Hypothetically, introducing friends from different social circles shouldn’t be that hard. Two people you like—and who like you—probably have some things in common. If they like each other, you’ll have done them a service by connecting them. And then you can all hang out together. Fun!

Or, if you’re like me, you’ve heard a little voice in your head whispering: Not fun. What if you’re sweet with one friend and sardonic with another, and you don’t know who to be when you’re all in the same room? Or what if they don’t get along? Worst of all: What if they do—but better than they do with you? What if they leave you behind forever, friendless and alone?

That might sound paranoid, but in my defense, it turns out these thoughts are common. Danielle Bayard Jackson, the author of Fighting for Our Friendships: The Science and Art of Conflict and Connection in Women's Relationships, told me that when she was a high-school teacher years ago, she’d often hear students airing anxieties: So-and-so’s befriending my friend or I think she’s trying to take her. She assumed it was a teenage issue—until she began working as a friendship coach and found that her “charismatic, high-achieving, successful” adult clients didn’t want to introduce friends either. The subject has been popping up online, too. A whole category of TikToks seem to consist of people just looking stressed, with a caption like “when your birthday is coming up and you gotta decide if u wanna mix the friend groups or not” or “POV mixing friendgroups and they’re about to watch you switch between personality 1 & 3.” In a recent Slate article, the writer Chason Gordon confessed to an “overwhelming horror at merging friend groups.”

Much of what can make linking friends scary—insecurity, envy, an instinct to hold tight to the people you love—isn’t new; it’s fundamentally human. But keeping your friends to yourself, what I call “friend hoarding,” is a modern practice. Before the Industrial Revolution, having different social circles was hardly possible: You were likely to eat, work, and pray with the same people day in and day out. Only once more people moved from close-knit farming villages to larger towns and cities did strangers begin coexisting in private bubbles and forming disconnected groups.

Today, this phenomenon has gone into “hyperdrive,” Katherine Stovel, a University of Washington sociologist, told me. With the internet and faster transportation, people can more easily maintain relationships from different parts of life; the more discrete the groups are, the harder it might be to integrate them.

But the thing is, many people want to benefit from the kinds of introductions they’re nervous to make. And ironically, though they might hoard friends out of fear of being abandoned, doing so could leave them feeling more lonely in the end. Marisa G. Franco, the author of Platonic: How Understanding Your Attachment Style Can Help You Make—And Keep—Friends, told me that people who have plenty of individual friends can still experience “collective loneliness,” or a yearning to be part of a group with common identity or purpose—something that a more connected, cohesive network could solve. Bayard Jackson mentioned something similar: “I've had people say to me how hungry they are to be a part of a friend group, this family feel,” she said. “And then in the same breath tell me they don't want to introduce their friends to one another. And I'll point out … do you understand how that doesn't work?”

If Americans let their friends mingle, they might form the communities they’ve been hoping for. But first they need to stop standing in their own way.   

Before the late 18th century, most relationships were either familial or, at least to some degree, practical; they were rarely just about having fun or developing intimacy, as friendship is usually conceived of now. But after industrialization, people suddenly had far more options in life: what they’d do for work, where they’d live, whom they’d meet. As Reuben Thomas, a University of New Mexico sociologist, told me, it became possible to be the only person “who works as a hospital technician but is also in a Sherlock Holmes book club, and is also in a rock-climbing club, who goes to Renaissance fairs and is part of the Swedish Lutheran church and lives in Wichita.” Each pocket of life can yield more pals.

These days, people can socialize online with scattered friends who’ll never end up at the same bar or party—and who might not even know of one another’s existence. Even if friends live in the same area, today there are fewer so-called third spaces: free, public areas where big groups can hang out. Just as romance has become privatized, with more people dating strangers from apps than acquaintances from their network, researchers told me that there’s been a shift toward privatized friendship too. “Everybody has to have a play date rather than just going out into the neighborhood and playing with whoever's there,” Stovel said.

Keeping friends separate can have its benefits. It allows people to freely express certain sides of themselves in the safety of simpatico groups—say, earnest geekiness with the Renaissance stans and adventurousness with the climbers. Stovel told me this can be particularly important for young adults, who might be “trying on personas” to figure out who they are.

[Read: What adults forget about friendship]

A more primal motivation also keeps many folks from making introductions: They’re nervous that their friends will grow close and that they’ll be cast aside. People have argued for decades that feeling threatened by friends’ other bonds is immature; or worse, that it reveals how capitalism has crept into relationships, driving us to compete, amass power, and treat one another like possessions, Jaimie Krems, a UCLA psychologist who studies friendship envy, told me. But the cold, hard fact, I’m sorry to report, is that friendship inherently does involve some competition. According to the “alliance theory,” humans have evolved to make friends because they’re in our corner—not someone else’s—in times of trouble, and we’re in theirs in return. Today, too, everyone has limited time, attention, and resources to share with the people they love, and more time with one friend inevitably means less time with another. Friendship envy is adaptive, Krems told me.

You can lose friends after introducing them; researchers have found that “friend poaching” is a very real phenomenon. But even if that worst-case scenario isn’t likely to happen, the thought of losing any closeness can be terrible. Bayard Jackson said that women in particular “really value feeling like we’re in this mutually exclusive private vault” with our besties. It’s cozy in there! And so many people already have a gnawing fear, she told me: “that I’ll be left behind, forgotten, that I don’t offer anything interesting enough.”

Being the person who introduces two friends—Stovel calls these people the “catalyst brokers”—nearly always involves some risk. Initially, the broker gains power because the two people she’s introduced are dependent on her for access; the friends are also, hopefully, grateful for the connection. At some point, though, the broker might become redundant, even disposable, the same way a matchmaker or a real-estate agent would be after a job well done.

People may have more to gain than they do to lose when mixing friends, though. Making those introductions might make you feel more whole, like the various versions of yourself are finally coming together. Combining circles could be the difference between sustaining friendships and letting them languish from neglect, given that finding time is a big obstacle to friendship today. Your friends may also be able to offer you more support together than they could individually, especially in a crisis; they can work together to care for you. And you might start feeling like part of something larger than yourself—a remedy for the “collective loneliness” that Franco described.

[Read: What if friendship, not marriage, was at the center of life?]

Drawing connections among people could even shift society as a whole, making it more equitable and less homogenous. For one thing, friend hoarding—however unintentionally—can lead to “opportunity hoarding,” in which privileged people circulate resources among themselves rather than distributing them to people with greater need outside their bubble. And if people all stay locked in the groups they formed from, say, high school, society is more likely to remain stubbornly segregated. The German philosopher and sociologist Georg Simmel believed that a society with separate but overlapping circles allows people to observe one another’s commonalities and differences, which, Stovel said, can “breed empathy, understanding, tolerance, and a richness of experience and curiosity.” It’s a sign, she said, of a “strong social fabric.”

This doesn’t mean that everybody needs to immediately invite all their buddies to the same place and keep the door locked until they’re ready to emerge as one mega-group. But maybe more people could start warming to the idea of being the broker. Bayard Jackson likes to remind people that friendships ebb and flow: Even if some of your friends do eventually get closer to one another than they are to you, that hierarchy isn’t static. And it might help to remember, too, that the reason this all can feel so hard is that friends mean so much. Krems believes that friend envy is functional in part because it motivates people to care for their relationships, to not take them for granted. In her research, she’s found that when people feel that their bond is threatened, they’ll take pains to protect it. This might involve telling a friend that you care about them—so much so that you fear them getting close to someone else, even if you know that reaction might seem silly.

The truth is that you probably can’t keep your friends separate even if you want to. You certainly can’t dictate whom they connect with. That’s the thing about friends: They’re not characters in your head but autonomous human beings with their own motivations and experiences. That’s why they’re interesting—and why they give us so much to lose.

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