This is a loop. Firstly people get spoiled. later fight and then they feel as if they fall off a horse and start behaving sensibly (you can call this period as a peace). Later this atmosphere of peace leads improvement. And people feel big and get spoiled again.
If you leave people alone this will go on like this. Only God's real religion can stop this. Otherwise people will just see materials when they look around. They will want to have all of it. More and more.
Materialist idea makes people harsh and greedy . People feel right as they crush weak one. This was available long before. Later they even made up Darwinizm for feeling peace while they crush others. This idea made them right on killing, exploiting , slaughtering. Remember Hitler, Mussolini, Stalin, Mao, etc. They did what they did coz they just know material. They carried out animal world's rules in a modern way.