I will grant that humans have always been beating on each other, but conflicts have always ended. There have been periods of peace between wars. Even today, it's not hard to imagine a future where two specific warring parties settle their differences and enter a period of peace.

But it has become nearly impossible to imagine a future where my country, The United States of America, is not actively involved in some conflict somewhere. I don't think my grandchildren will ever know a time when there are no US soldiers shooting at, US planes dropping bombs on, or US drones shooting missiles at someone in some foreign country. That is the definition of perpetual war.