The introducers here did not necessarily intend for the two people they introduced to become partners, but the introduction nevertheless had this effect. Roughly 68 percent of the people in the study met their spouses after being introduced by someone they knew, while only 32 percent met via “self-introduction.” Even for short-term sexual partners like one-night stands, 53 percent were introduced by someone else. So while chance encounters between strangers do happen, and while people sometimes find their partners without assistance, the majority of people find spouses and partners by meeting friends of friends and other people to whom they are loosely connected.

      While friends were a source of introduction for all kinds of sexual partnerships at roughly the same rate (35–40%), family members were much more likely to introduce people to their future spouses than to future one-night stands. And how people meet is also relevant to how quickly they have sex. In the Chicago study, those who met their partners through their friends were slightly more likely to have sex within a month of meeting than those who met through family members. A similar study conducted in France found that couples who met at a nightclub were much more likely to have sex within a month (45 percent) than those who met at, say, a family gathering (24 percent), which is not surprising since one typically does not have sex in mind at family events.³

      These data suggest that people might use different strategies to find partners for different kinds of relationships. Maybe people ask family members for introductions to possible marriage partners and rely on their own resources to meet short-term partners. This makes intuitive sense: most drunken college students are not texting their mothers to see if they should invite that cute stranger at the bar home for the night. So, what you get when searching your network depends in part on where you are looking and what you are looking for.

      However, it is clear that people rely heavily on friends and family for all kinds of relationships. When you meet a new person on your own, you only have information about yourself. In contrast, when others introduce you to someone new, they have information about both you and your potential partner, and sometimes they play the role of matchmaker (consciously or not) by encouraging meetings between people they think will get along. Friends and family are likely to know your personalities, social backgrounds, and job histories, and they also know important details such as your tendency to leave underwear on the floor or to send roses. The socially brokered introduction is less risky and more informative than going it alone, which is one reason people have relied on introductions for thousands of years.

      Yet in most modern societies, we generally have a negative view of arranged marriages, and we cannot possibly imagine what it would be like to marry a stranger. Well-meaning friends and relatives who nosily interfere in our lives to help us find partners are seen as comic figures, like Yente in Fiddler on the Roof. But, in fact, our friends, relatives, and coworkers typically take on a matchmaking role only when they think we are having trouble finding a partner on our own. And as it turns out, our social network functions quite efficiently as matchmaker, even when we insist we are acting out our own private destiny.

      The structure of naturally occurring social networks is perfectly suited to generate lots of leads. In networks such as bucket brigades and phone trees, there are only a limited number of people within a few degrees of separation from any one person. But in most natural social networks, there are thousands. As we discussed in chapter 1, if you know twenty people (well enough that they would invite you to a party), and each of them knows twenty other people, and so on, then you are connected to eight thousand people who are three degrees away. If you are single, one of all these people is likely to be your future spouse.

      Of course, random encounters can sometimes bring strangers together, especially when incidental physical contact is involved. These happy accidents are frequently used as plot devices in romantic stories, whether it’s two people grabbing the same pair of gloves in Serendipity, an umbrella taken by mistake after a concert in Howard’s End, or dogs getting their leashes entangled in 101 Dalmatians. Incidents like these provide opportunities for further social interaction, and possibly sex or marriage, because they require what sociologist Erving Goffman called “corrective” rituals: people have to undo the “damage,” and this in turn means that they have to get to know each other. Good flirts are able to turn such happenstance into real opportunities. And the best flirts may even be able to contrive an “accident” in order to meet someone: they make their own luck. But these are the exceptions more than the rule. And it is noteworthy that even these meetings of strangers involve some degree of shared interest, whether in clothing, music, or pets, for instance.

      Even when people meet on their own, without help from mutual contacts, there is a social preselection process that influences the kinds of people they are likely to run into in the first place. For example, the Chicago Sex Survey also collected data on where Americans met their partners. Sixty percent of the people in the study met their spouses at places like school, work, a private party, church, or a social club—all of which tend to involve people who share characteristics. Ten percent met their spouses at a bar, through a personal ad, or at a vacation spot, where there is