A Sense of Belonging?

     Okay, back to "us" vs. "them" mentality...
     Humans are social creatures, yes? I presume that means we feel a strong need to belong to a group of other humans. But is it just not enough to belong to the group of humanity as a whole? Is that too large and vague a group for us? Do we have an innate need to create and categorize smaller groups and sort ourselves into one or more of them? It seems we are constantly making observations and, consequently, judgments about those around us. And I would conclude, based on the conversation of those around me, that the judgments we make often reassure us that we're better than those we observe in some way.
     So is the grouping all about shoring up our self esteem by placing others in inferior groups and ourselves in a superior group? Or is it more about breaking something large and vague down into more manageable and comprehensible subsets? To restate it: do we judge others to make ourselves feel better than them and, thus, about ourselves, or because we have trouble feeling a real sense of belonging in such a large group as the number of persons living on the earth today and need smaller, more specific guidelines for the clan we identify ourselves with?
     And that last question makes me wonder if we're simply more comfortable with a labeled world? Do we feel safer if we can put others into categories somehow, as if that will help us know what to expect from them at all times? Are we driven by a fear of the unknown and a fallacious belief that, if we can just pin others down and post a label on them, we will then know everything we need to know about them so as not to be surprised by them in some way in the future?
     Anyone got any thoughts, theories, questions to add? I'm still mulling this all over. Meanwhile, I'm gonna go put myself into a subset of people who ask a lot of questions...