Analysing the human race

Time and again I am horrified by what people are capable of doing to each other. Gladiator combats in ancient Rome. Slavery in America. The Holocaust in Europe. The world's history is a history of violence and it has become worse throughout the centuries.
Murder, abuse, torture, war, death - it all belongs to today's normal life.
I am scared - deeply petrified - that someday absolutely nobody will care anymore. From that moment onward, indifference will slowly and unnoticed turn into hate. Hate leads to killing leads to suffering leads to more hate. A never ending circle.
And the question everyone asks but no one is able to anwer? Why.
I found my own answer: It's because the human being is destined to long for more. More money, more influence, more power. And being an inherent feature of mankind, it will never stop.