A year ago (summer 2018), this line of thought occurred to me when I went on a walk.
When population is less, people understand that they must give up petty struggles and cooperate for both parties to succeed. Once a people get prosperous, their needs met, they start to compete rather than cooperate. Or worse, they start to flaunt to the same people whose ancestors helped their ancestors establish society on moral principles.
As the population grows, people break into groups. If their leaders are incompetent, they start to live in separate socioeconomic orders (nations and states), losing opportunities they could have if they traded freely. When more and more people get added to the system, which is divided and competing against one another, instead of cooperating, they no longer care for another. I mean there are too many people. Suddenly, it no longer matters that too many can undertake great projects if they were not so pathetic to one another.
Soon, they wage wars thinking they can get somewhere with it. Both sides inevitability get worse off post-war. Those who fight rather than cooperate oppose the higher order. Those who do not fight are likely to remain alive and pass their values to their descendants.
In other words, non-cooperation seems to be a violation of the higher-order. Those who violate it must die off so it can be restored. Perhaps, this is the natural order.