People should get along and cooperate to achieve shared goals, but we don't. Not only don't we do this, but in fact our world is dominated by war, terrorism, fanatic oppression, and every imaginable brutality. It isn't unusual for people to assume the best about humanity and speak of our terrifying destructive potential as something which is at odds with our nature, but a close look at history shows that brutality, oppression, and most of all war are endemic to human cultures. Peaceful coexistance is the exception. More than merely being troubling, this bodes ill for the survival of the species in general.