One would assume that evolution would apply on the somewhat macro scale as well. So in a situation where humanity is spread thin across the countryside, evolution would select the independent, savage, antisocial individuals. In situations where large numbers of people are forced together regularly, it would be the gregarious, tolerant, social individuals who will survive.
When spread thin, the social ones will fade since they get no support/reinforcement.
When packed tightly, the antisocial ones will fade because the social ones will gang up and eliminate them.
Sounds convincing. But I believe an argument to the contrary can also be made.
When humans were still spread very thin on the ground, in stone age tribes consisting of a couple of hundred or so individuals at most, the survival of any single individual was contingent upon the support and protection he received from his fellows. Antisocial, treacherous, or down-right dangerous behavior directed at others would presumably have decreased the support the offending party received in the future, and in extreme cases could result in banishment from the tribe. Which would have been tantamount to a death sentence, as a flintstone spear made for a poor defence against a cave bear or a smilodon. Co-operation was necessary for survival, and given the low level of sophistication in conflict resolution mechanisms, such things as honor and reputation mattered for much (nowadays a person is given a fair shake in a court of law even if they are the scum of the earth and everybody knows it). Those traits are still in evidence among primitive societies today; I seem to recall how comparing results cross-culture in an anonymous dictator game (or some similar game, but it was anonymous), it was found that some mongolian nomads scored the highest points for altruism, though for the life of me I can't find the source.
Also, competition for resources has been identified as a major cause of conflict. A situation where there are fewer people around would leave more resources per person, thereby presumably diminishing the relevance of this particular cause and negatively affecting the cost-benefit analysis of the aggressor. The more people you have, the more competition there is, with a Malthusian catastrophy as the extreme (if outdated) example.
As to the modern condition where people are packed tight, I do agree that public (noticed) anti-social behavior is a very significant disadvantage. Witness the uproar over Mitt Romney and Bain Capital. But if we go with altruism, being 'good' and 'playing nice', then if those were the qualities that yielded an advantage in today's society, shouldn't we expect to see them in abundance in the people who are most successful? Because I'm not sure we do, or rather we might see their PR, but the reality might well be quite different.
Seriously though - it's a balancing act, and one I feel is self-balancing. There's the upward push of humanity's desire to climb to better things, balanced against their bestial nature to kill everything they can't fuck. I favor extremely limited government because government itself is comprised of people (as Shepherd Book observes, themselves largely ungoverned), and wielding power often turns these people into tyrants of one flavor or another - be they self-serving or ubernannies. In other words, yes, human beings are inherently evil, largely uncorrected, and are able to do more evil the more power they have, and thus, should be trusted with as little power over each other as can be had without devolving into the anarchy that Hobbes describes.
If I may, I'd like to ask a couple of questions to clarify.
You mentioned a self-balancing act between the evil nature of man, and 'the upward push of humanity's desire to climb to better things'. Do you mean that this upward push is something like a communal sentiment for social justice, indicating that man is not thoroughly wicked? Or is it some lesser form of Hobbes' social contract, where a group of selfish and vile creatures agree to mutually limit their range of options in order to gain a measure protection from the depredations of each other? Or did you mean something else?
Would your night watchman state have any mechanisms to address social, economic, and political evils in the interests of internal stability, or would it be left to the kindness of the elites to see to the less fortunate?
