Human aggression

That man is an aggressive creature will hardly be disputed. With the exception of certain rodents, no other vertebrate habitually destroys members of his own species. No other animal takes positive pleasure in the exercise of cruelty upon another of his own kind. We generally describe the most repulsive examples of man's cruelty as brutal or bestial, implying by these adjectives that such behavior is characteristic of less highly developed animals than ourselves. In truth, however, the extremes of 'brutal' behavior are confined to man; and there is no parallel in nature to our savage treatment of each other. The sombre fact is that we are the cruelest and most ruthless species that has ever walked the earth; and that, although we may recoil in horror when we read in newspaper or history book of the atrocities committed by man upon man, we know in our hearts that each one of us harbors within himself those same savage impulses which lead to murder, to torture and to war.