Evolutionary preconditions for inhibition of intraspecific aggression

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The full article with all sources can be found on the main page: https://antiviolence.io/en/#inhibition_of_intraspecific_aggression

The analysis of intraspecific aggression should begin with a consideration of its positive aspects, which later will allow us to avoid some misunderstandings. Aggression, including violent one (i.e., physical harm and murder), allows the stronger and healthier individuals in the population to prevent the weaker and unhealthy individuals from procreating. Also, it is beneficial for a particular individual, which is able to use it for the sake of its own survival and to pass on its genes further. It also serves as a tool in creating and maintaining a dominance hierarchy that coordinates the actions of otherwise scattered individuals. Finally, since aggressive behavior does not allow different individuals or groups of individuals to stay close for an excessively long time, this leads to their even distribution over the entire territory available for habitation and hence to the even distribution of limited resources.

Nevertheless, do not make a mistake of looking at violence in isolation from circumstances and factors of the environment. In this case, the two most important are: the presence of strong innate armament in some species and their inability to escape from violence (due to limited area of habitat, social behavior, or other reasons), which will lead to frequent conflict situations. The stronger these two factors are, the higher the risks of violence. At a certain point, the risks become too high for the benefits derived from violence to offset them. Violence ceases to be an evolutionarily stable strategy of behavior. And its risks can grow up to the point that individuals simply exterminate each other in violent fights and destroy their population.

If members of a population have strong innate armament, then the individuals which are most prone to violence will encounter the armament of their conspecifics if they initiate attacks, and this can often lead to their death. Also, disastrous for the aggressor may be the resistance of the armed victim, which has nowhere else to escape. Even several victories in such a situation cannot guarantee the evolutionary success of the aggressor since one of such attacks is still likely to end in its death. At the same time, less violent individuals will die less often since they do not initiate attacks but only defend themselves. They will be less likely to face the risk of dying from violence than their aggressive conspecifics, which means they will more often have offspring.

As a result, natural selection has to move towards the development of strong inhibitors that prevent harming and killing among conspecifics since individuals lacking such inhibitors will likely be removed from the population, not being able to pass on their genes further.

Observations of animal behavior support this conclusion. The concept of aggression inhibitors was first formulated by the ethologist Konrad Lorenz. According to his theory, this mechanism is most developed in those species that are able to easily kill an individual of approximately their own size. Describing his own observations of wolves, Lorenz showed how aggression inhibitors are activated when one wolf demonstrates to another a gesture of submission or vulnerable parts of its body, such as the neck or belly. As a result, a petrified aggressor cannot continue the attack. Also, observations of ravens showed that they do not peck out each other's eyes, even during fights.

The ethologist Irenaus Eibl-Eibesfeldt listed many such observations from various researchers. Fiddler crabs, due to their anatomical features, do not open their claws in fights wide enough to injure an opponent. Many species of fish, lizards, and mammals are characterized by the ritualization of fights. A noteworthy example is oryx antelopes, which carefully handle their sharp horns in fights with other oryx, but at the same time use them to the full extent in defense against lions. It is also worth mentioning venomous snakes, many of which squirm, bloat, and push each other during fights but do not bite or even display their weapons. Even very primitive creatures have a similar mechanism. So, jellyfish, including the extremely deadly box jellyfish, have a chemical blocker that prevents their tentacles from releasing poison when they collide with a conspecific. At the same time, all other creatures are stung automatically.

Aggression is less inhibited in weakly armed species. Compared to ravens, turtledoves with a less sharp beak can even kill a conspecific if it is deprived of the opportunity to escape (for example, when placed in a cage). Under natural conditions, conflicts do not threaten the survival of turtledoves in any way, they are unable to kill a conspecific quickly, and it can easily escape.

Animals with a solitary lifestyle are also quite aggressive. If we consider their case in more detail, then its evolutionary influence can be equated to a form of escape. In that way, violence cannot threaten the survival of polar bears or jaguars, which out of the breeding season rarely cross each other's paths for the resulting fights to have any effect on the population as a whole. It is also important to mention the example of lions. Their aggressiveness can be explained by social factors. For example, each pride has only a few males, and young ones leave it when they reach a certain age. Also, some ethologists say that the reasons for the high aggressiveness of lions are not yet fully understood, however, within one pride aggression is still inhibited.