Maybe we aren't supposed have peaceful, advanced societies. Maybe we are supposed to be swinging in trees and constantly at war with the neighbouring tribe.
Great reply :) but really, why people so often think "we're supposed to be" anything at all? Life seems totally random. We're not supposed to be anything, we just make it all up as we go. Money, happiness, love... we make it all up on top of our basic emotions (you could claim emotions guide what "we're supposed to be" in which case your reply is the conclusion we arrive at).
Think of the idea of a self reinforcing meme. If people think we are supposed to be, then we will be. "By force if necessary". Typically individuals that fall too far out of what society expects may be culled by one means or another leading to a cultural definition of 'supposed'.
