Almost all the important stuff civilization has accomplished has come about because people got together in groups and bounced ideas off each other for a while. The bigger the groups, the longer the associations, the greater the achievements. The downside is people are still at least a little like animals, so when you pack them in close together they become more dangerous to each other for lots of reasons.
People also fuck...a lot...no matter where they are. In cities with diverse, changing populations, they fuck whoever's nearby, which means diversity in the end, thought to be good. In the sticks, they fuck whoever/whatever they can reach on a tank of gas (at least, these days...), so there's a good chance they're only a couple of generations apart. If the population is denser and cultures diverse, disease can also spread more rapidly. In rural areas, it's the opposite.
Everywhere I've been, city folk think rural folk are nuts and genetically questionable, and vice versa. Both groups also suspect they don't need the other. Since there's both street hooker and farmer's daughter pr0n in abundance, however, I conclude both approaches to life are essential for survival of the species on some deep-down level
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