This is one of the largest life secrets: our roots dictate who to be friend with. People may have good intent to mix with different tribes but always end up friend with those of similar minds. This is because roots have powers beyond our control: they set up comfort zones for ourselves.
Consider this study, conducted by Paul Ingram and Michael Morris at Columbia University. The psychologists invited a motley group of executives to a cocktail mixer, where they were encouraged to network with new people. Not surprisingly, the vast majority of executives at the event said their primary goal was to meet “as many different people as possible” and “expand their social network.” Unfortunately, that’s not what happened. By surreptitiously monitoring the participants with electronic name tags, Ingram and Morris were able to track every conversation. What they found was that people tended to interact with the people who were most like them, so that investment bankers chatted with other investment bankers, and marketers talked with other marketers, and accountants interacted with other accountants. Instead of making friends with strangers, the business people made small talk with those from similar backgrounds; the smallness of their social world got reinforced.