One thing that’s always struck me about American politics is the fact that there’s a tremendous amount of rancor over largely uninteresting issues. Most of the political debates between the left and right are over things like whether the top tax rate should be 39% versus 30% or whether gays should be allowed to marry. Compared with with just a couple political debates plucked from history — should we actually murder all the Jews, or just drive them from our lands, or slavery: good or bad? — modern political tussles seem rather meaningless.

Nonetheless, there’s a lot of heated emotion. The general view from the left seems to be that you can’t just disagree with conservatives, you must hate them with every fiber of your being, and the inverse is true from the right. People go to great lengths to segregate themselves from people who don’t think like they do. There’s really two interesting psychological concepts here. One is that people break the world into two parts (as opposed to threes, or fives, or tens), the other is that people then separate these two parts from each other by ocean wide distances.

The latter might make some sense from an evolutionary perspective. When we existed in small tribes, the rest of the world really was out to destroy you, so it was pretty easy to assign the worst motivations to the “them” in “us and them.”

But why do we split things in two? You see it not just in politics but in many aspects of culture: the Asian yin and yang, the general battle between good and evil mythologized in many cultures. I was wondering if there might be some neurological explanation for this — some part of the brain that for whatever reason is predisposed towards bisecting things. But then an interesting insight occurred to me: we have two hands. Is it as simple as the idea that we have spent our evolutionary lifespan saying “on one hand you have this, on the other hand that”?