Why have humans always slaughtered each other?

War, unbalanced countries , huge divide in living conditions yet we are the only species that know our fate is death' on this small blue ball earth that was given mm perfect yet we do nothing but destroy damage , an poison our home . Kings through the centuries till Now. Is asking for every human to live in peace so inconceivable we could' cultivate our world an harvest so people could have lived as equals , But NO humans choose the path of greed' an blood' for power' borders , We have everything yet nothing , yet centuries ago our ancestors had nothing like modern age but could produce pure genius eg Michelangelo / Pyramids/ we can't even decide on medicine, or Food, humans have declined , This is the dark ages . we slaughter, seems like WAR we are the cancer. from 1066 to BC bloodshed why that's all ,Please excuse my punctuation i suffer