We humans can't seem to avoid war, because we humans simply do not see ourselves as all members of a single family. And because we do not hold our leaders -- for the most part -- accountable. The Pope, just for example, is there for life -- and when he decides to speak ex cathedra, it appears he's also "infallible." Donald Trump is deemed almost a god by an enormous number of Americans, which just boggles my mind. And the ideologies and weird beliefs we cling to, and how we fear those not quite like us, instead of getting to know them. The Pope says "peace" is the answer, I say "familiarity" is the answer. You cannot fear that with which you are familiar and understand.
I quote again from Carl Sagan, from "Pale Blue Dot," speaking about the earth as seen looking back towards the sun from Saturn, a tiny blue dot seen through one of Saturn's rings. The Earth is, he says, home to:
The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every "superstar," every "supreme leader," every saint and sinner in the history of our species lived there-on a mote of dust suspended in a sunbeam.
The Earth is a very small stage in a vast cosmic arena. Think of the endless cruelties visited by the inhabitants of one corner of this pixel on the scarcely distinguishable inhabitants of some other corner, how frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds. Think of the rivers of blood spilled by all those generals and emperors so that, in glory and triumph, they could become the momentary masters of a fraction of a dot.