You're talking about the Paleolithic Era, when we lived in small extended-family units. Everyone had known, trusted and cared for everyone else since birth. We are a pack-social species and our pack-social instinct served us very well in those days.
Of course hunter-gatherers never have a food surplus so they're always one bad year away from a famine. So the down side of our instinctive Paleolithic morality was that we regarded other clans as competitors for scarce resources. If they intruded on our precious territory violence was likely.
The Agricultural Revolution allowed us to grow our own food, requiring us to build permanent settlements. Economies of scale and division of labor made it attractive to invite other clans to live with us, but this required overriding our instincts and learning to live in harmony and cooperation with people we hadn't known intimately from birth.
Civilization took this one step further. Building cities with trading networks resulted in a bounty of food as well as man-made artifacts like furniture, pottery, clothing, musical instruments and works of art. But it required us to live in harmony and cooperation with strangers. This goes completely against our instincts. To help us deal with this unnatural way of life, we developed many new institutions such as laws and a social hierarchy, which evolved into government, and many new technologies such as money and recordkeeping, which evolved into written language. This imposed order on us, making us, artificially, herd-social instead of pack social: treating anonymous strangers with a minimal level of respect
But all of this happened in a mere twelve thousand years, and this is not enough time for a species with a 15-25 year breeding cycle to evolve new instincts to adapt to it. We're not bacteria, who go through several generations in a day and whose evolution can keep pace with their environment. Deep down inside, we're all still cavemen, regarding strangers with suspicion rather than love and harmony. The proof of this is that every so often one of us reverts; his stifled inner caveman rebels and strikes out, committing an act that would have been natural and survival-oriented in the Paleolithic Era, but today is regarded as anti-social, or downright criminal. Occasionally, encouraged by the Stone Age religions that are still among us with their "we're better than everybody else" mandate directly from their gods, entire communities of humans rise up in violent confrontation with their neighbors, overwhelming these institutions of imposed harmony. If you're concerned about prostitution, how do you feel about war?
You're going to have to give our species another ten thousand years or more, before our instincts evolve to keep up with our new social organization. In the meantime we absolutely need all of these artificial buttresses that keep civilization running, such as money and laws.
Of course civilization, this artificial super-organism we have created, of which we are the cells, evolves at a much faster rate than biological organisms. By the time we've outgrown our inner cavemen, our social structure will be way ahead of us and we'll still need artificial constraints to live within it.
