It seems human aggression is more prevalent today than ever. Man is the only animal that practices war and mass murder. The key seems to be in our social learning process.
Aggression is everywhere, everyday.
Wars, examples of sanctioned aggression, and murders, examples of hostile aggression are the most publicized. However, more subtle forms of aggression stemming from the desire to achieve a goal, or the desire to deny someone else their goal are just as common. Males show higher levels of physical aggression, while females are more verbally aggressive. This aggression results from a combination of heredity and environment, with a major emphasis on environmental factors. Gender roles are one reason for this.