The Aggression Systems
Evolution of Aggression - Introduction Page 9

Table of Contents


Preface Pages 1 - 2


Human aggression - introduction Pages 3 - 4 - 5 - 6 - 7 - 8


Evolution of aggression - introduction Pages  9 - 10 - 11 - 12 - 13 - 14


Brain mechanisms of aggression - introduction Pages 15 - 16 - 17 - 18 - 19 - 20


Dynamics of aggression - introduction Pages 21 - 22 - 23

In this section we will trace the transformation of the offense motivational system of animals into the behavior of anger that is characteristic of humans. We will show that there is a fundamental continuity to these phenomena, and that the evolutionary transformation from one to the other has taken place according to a general law of evolutionary change in motivational systems.

By concentrating on offense in animals and anger in humans, it will be possible to consider the evolutionary origin of most human aggression. However, there are other types of aggression that are also important, and should be mentioned, although they will not be dealt with in this section.

In addition to angry aggression, humans engage in a form of aggression that is totally unknown in animals: institutional aggression. Institutional aggression includes the behavior of people serving in institutions such as the military, police and security forces, criminal and terrorist groups, armed revolutionary forces, etc. As shown in the paper There Is No Instinct for War, the motivation of individual participants in institutional aggression does not necessarily include anger or any other motivation that can be found in animals.

There are also certain categories of animal aggression that will not be considered in this introduction, because they are not controlled by the offense system. Some of them may also occur in humans, although they tend to be rare and special occurrences. Four categories should be mentioned.

  • Defensive aggression. This is the aggression that may take place when an animal or person is injured or threatened with physical injury. Just as we recognize that a frightened and cornered animal is dangerous, so, too, we recognize that the same phenomenon can occur in people. Defense behavior is analyzed here in the comparative review of muroid rodents.
  • Maternal aggression. It is common knowledge that animals defending their young can be especially dangerous to anyone who tries to disturb them, and whether or not this occurs in humans has not yet been scientifically determined. As discussed in the review of muroid rodents, maternal aggression may reflect simultaneous activation of offense and defensive attack.
  • Predatory aggression. Carnivorous mammals have a separate system of predatory behavior, based on a brain organization that is separate from offense and defense (see paper on ventromedial tegmental lesions in section on brain mechanisms). Predatory attack may occur on rare occasions in humans; for example, the wild boy of Avignon was said to have killed his prey by a bite to the back of the neck as do other mammalian predators.
  • Group display. This behavior which is characteristic of primates, as described in the papers here concerning monkeys, may serve, in some contexts, as an aggressive threat. It apparently represents an independent motivational system, although little is known about its brain organization. It certainly occurs , in humans as well, where its function ranges from the cheering at a sports event to the aggressive cries of a lynch mob.

(Continued on next page)

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