In the United States, urban and metropolitan areas of the country seem very polarized against rural areas of the country. This is an important aspect of American political and social polarization that plays out in how we vote and how we think. Denser areas and higher population areas tend to vote for Democrats while rural areas tend to vote for Republicans. Urban and metro areas are more favorable to immigration and gay marriage than rural areas. Living in larger and denser cities seems to shape the way people think about social issues and how they ultimately vote.
This is not necessarily a surprising issue and reflects self selection effects and general life experience effects on the way we think about people and the world. The more you are exposed to diverse and different people, the more likely you are to be accepting of them, at least if your encounters with them are generally positive.
Steven Pinker writes about this phenomenon in his book The Better Angels of Our Nature, specifically addressing how the spread of ideas and the spread of people has created a less violent world. As we have been better able to mix and interact, we have become a more tolerate species. Pinker writes,
“Why should the spread of ideas and people result in reforms that lower violence? There are several pathways. The most obvious is a debunking of ignorance and superstition. A connected and educated populace, at least in aggregate and over the long run, is bound to be disabused of poisonous beliefs, such as that members of other races and ethnicities are innately avaricious or perfidious; that economic and military misfortunes are caused by the treachery of ethnic minorities; that women don’t mind being raped; that children must be beaten to be socialized; that people choose to be homosexual as part of a morally degenerate lifestyle; that animals are incapable of feeling pain.”
While it is tempting to match all the examples from Pinker in the above paragraph to current American Political parties and dynamics, I think (and I believe Pinker would agree) it is more powerful to map this back to different cultures, different eras, and different human outlooks and beliefs throughout the history of mankind. We evolved within small tribal groups and slowly developed cities. However, our cities were never as interconnected as they are today. It was possible to think of people who didn’t speak your language or live up to your customs as savages. This seems to be a typical way of thinking for humans, especially when there isn’t anyone or anything available to prove you wrong. It is easy to imagine that the Greeks effectively dehumanized the Trojans to justify destroying Troy. While this has still happened in modern times (the Nazi’s dehumanization of Jews as an example) it is harder to justify today. Our institutions and reformations recognize that there is very little meaningful difference between human races at aggregate levels, that human sexuality is far more complex than male/female, and ideas around compassion for the planet and animals have grown. Creating an interconnected planet has made us a more peaceful species over time by helping us learn more about different humans in different places with different customs but similar emotional and mental capacities to ourselves. The spread of ideas has made us more tolerant and has reduced violence.