What is especially perverse about this radical “bifurcation” in our social behavior is that it can be very labile. Our attitude can flip from one pole to the other on short notice, and with seemingly little pretext. Thus, a formerly hated enemy can become a highly respected ally – like Japan and Germany after World War Two. We may grow up in one country and then emigrate and become enthusiastic patriots of another country.

Likewise, a school or college that we formerly knew nothing about can quickly become “our” team once our application has been accepted. We unconsciously bond emotionally with our “in-group,” and come to view the students from other schools as rivals or opponents. Or we may embrace a charismatic new political candidate and actively support him/her while developing negative feelings toward his/her opponent. In short, we are very prone to polarize our social relationships, sometimes with life and death consequences.

We can make sense of this psychological puzzle by putting it into an evolutionary perspective. Our species has a very deep history, going back perhaps several million years, of living together in small close-knit, interdependent bands or “tribes”. Over thousands of generations, our ancestors’ interests were bound up with the cooperative efforts of their group with regard such vital things as finding food, access to fresh water, securing a safe shelter, sharing a warm fire, and especially collective defense against competing groups and the many other large animal species (most now extinct) that once preyed on them.

The emotional repertoire of our species – “human nature” – is a reflection of this group-based evolutionary history. We remain tribal animals to this day. Indeed, the modern world is a maze of tribes and sub-tribes – organized groups with shared interests – literally spanning the entire globe. Modern-day group behaviors, from national rivalries to ethnic and religious wars, corporate business conflicts, political partisanship, Superbowl Sunday, and much more, are a perpetuation of this deep-rooted social psychology. The universal tendency to align ourselves with one or more of the myriad of tribes in modern societies reflects the enduring power of our innate propensity for in-group attachments and out-group antagonisms.

If we are looking for a reason to hope that we might ultimately be able to transcend this tribalism, or at least diminish its importance to the arena of Monday night football, we can perhaps find it in the continuing, powerful linkage between tribalism and our self-interests. To the extent that we can build a global network of common interests – tribalism on a global scale – and diminish the importance of more parochial and divisive interests, we may ultimately be able to convert more and more of “them” into more and more of “us”. That is one of the great challenges for this century. – BY PETER CORNING