I feel very uncomfortable with how political ideologists try to push humans into "behaving" under the assumption that "humans must be forced to be good" because otherwise we would "regress into smashing each other's skulls like cavemen".
The idea that humans are inherently evil and sinful is very old. The Old Testament is built on this idea, Hobbes declared that humans are evil wolves, and one of Freud's basic ideas is that civilization was created out of the need to tame man's destructive tendencies — including the legendary "death instinct", which I believe only fictional lemmings in computer games have.
But civilization did not evolve to fight human instincts any more than termites or ants build their own colonies and even agricultures in order to fight the terrible death drives of the ants and prevent each other from regressing into cave ants. We humans came up with the division of labor for the same reason ants did — because organizing our lives together is a pretty smart thing to do.
In the past, many psychologists demonstrated how badly humans can treat each other — think of the Stanford Prison experiment, the Milgram experiment, various game theory experiments, or even the profitable pop-culture version, the Big Brother reality TV shows. I am not impressed with such set-ups. Prisons and TV shows are not a natural human environment. They are extreme situations that only show how extreme humans can get. How groundbreaking is it to put ten rats in a cage and let them fight over a tiny piece of cheese? Can anybody learn anything from this kind of psychology?
Even the assumption that scarcity is normal and natural and that we must fight over our resources is a fallacy to begin with — ask any child whether they like "musical chairs" game (also known as "the journey to Jerusalem"). No group of children would play "Let's see who gets the only place in the lifeboat while everybody else goes down with the Titanic" unless they are being made so by a slightly sadist grown-up. Children usually set up rules for their games that are accepted as "fair" by all so that everybody can enjoy the game. They will take into account that some children are weaker and should be given a headstart — not just to protect and help them, but also so that the older and stronger children can enjoy the challenge. A victory means very little if it doesn't come with the feeling that you earned it.
The one experiment in human nature that impresses me more than anything any professional psychologist ever came up with is the Free Hugs campaign: one person stands in a public place, holding up a sign saying "Free Hugs". This is a pretty natural human environment, and a very human challenge. Wherever this experiment ends up with total strangers hugging each other just because it feels good, we have reason to believe people are living under halfway humane conditions.