Why do we see aggressive behavior in all animal species, including in humans? What is its usefulness?
From an ethological point of view, aggression is a behavior which allows for a hierarchical status to be established within a group, facilitates the access to resources, allows one to defend against the attackers, ensures the territorial defensive or the conquest of other territories, helps one to protect the individuals from the native group, favors us in the contest with other males for the conquest of females, helps us to protect our sexual partner and to dispirit our rivals from other assaults in the future and so on. Practically speaking, the role of aggression is crucial for the existence, protection and evolutionary adaptation of the individual and the group [Kaufmann, 1965; Buss, Shackelford, 1997, apud Goetz, 2010, p. 17; Buss, Duntley, 2002].
There have been numerous and substantial potential advantages of aggression which have ensured the survival and the reproductive success of individuals so much, that, respectively, there have been enough reasons for the consolidation of these behavioral mechanisms on different stages of evolution, on a genetic level. We try to assign rational motivations to these acts; we label them as being immoral. However, they are, primarily, evolutionary adaptations, even if they seem to be ill-suited nowadays, and some manifestations of the instinct of aggression, such as homicides, military interventions, rapes, massacres, genocides and identity conflicts, are downright horrible [Duntley, Buss, 2011].
Let us examine a practical and recent example from the living world and see how the aggressive behavior can be advantageous for the ascension of a species. It’s about Dikerogamarus villosus, a species of shrimps which is also called “the killer shrimps” – a particular rapacious species, that succeeded in spreading panic among the European hydrobiological experts. These shrimps usually populate the rivers of East Europe, but in recent years, they have emigrated into the water of the Western Europe, where they proved to be a “total killer” of the microfauna from the local waterbodies.
This little crustacean of only 3 cm in length and with powerful mandibles kills and cripples, unselectively, everything it meets along the way and can knock down other species of shrimps, the offspring of fish and amphibians, small fish, aquatic insects, worms and other beings that are unable to run or protect themselves. The thing that surprised the researchers was that the “killer shrimp” kills more than he needs in order to feed himself; he kills in order to exterminate all the other potential competitors. We could say that he kills in a “genocidal” manner.
Due to his ferocity and high prolificacy, the “killer shrimp” colonized new and new aquatic spaces in Western Europe almost unrestrictedly (with a speed of about 124 km per year); he destroyed the populations of other species of shrimps (species that were also invasive), he imposes his status of an absolutely dominant species in the limits of the European aquatic microfauna and he smashes the ecological links that has stabilized themselves over the decades  [Macneil et al., 2013]. This is how, due to an extraordinary aggressiveness, a species manages to eliminate its competitors, to invasively expand its living area and to multiply, in order to raise its evolutionary opportunities for a long period of time.
Of course, aside from competition through aggressiveness, there are other strategies in the living world which are used by some species (and nations) to ensure their survival and to gain evolutionary advantages, strategies like cooperation, reciprocal altruism, coalition formation etc., but no other strategy seems to be so omnipresent and efficient as the one that implies fighting for survival through… fighting.
The aggression has foreshadowed the history of the human society itself. First, during the prolonged period of our species evolution, then in the process of geographical expansion and social affirmation, the aggressive behavior represented a compulsory factor for the ensuring of the existence and perpetuation of an individual, a group or a nation. This behavior had an adaptive role, i. e. it facilitated the survival and the reproduction of the individuals and the groups which demonstrated a higher capacity of combativeness and which used the aggression as a tool for protection and conquest.
There are studies showing that overconfident states predominate in the population at the expense of unbiased or underconfident states. Overconfident states win because: (1) they are more likely to accumulate resources from frequent attempts at conquest; (2) they are more likely to gang up on weak states, forcing victims to split their defences; and (3) when the decision threshold for attacking requires an overwhelming asymmetry of power, unbiased and underconfident states shirk many conflicts they are actually likely to win. These “adaptive advantages” of overconfidence may, via selection effects, learning, or evolved psychology, have spread and become entrenched among modern states, organizations and decision-makers. This would help to explain the frequent association of overconfidence and war, even if it no longer brings benefits today [Johnson et al., 2011].
Political scientists admit the fact that the shy and peaceful nations stood to lose during territorial competition, just as the fractions which exhibit weakness and insufficient incisiveness stand to lose during competitions for power. On a political or geopolitical level, those who use the tool of violence and pressure have a higher chance of reaching their goals, and a force which has political power can be combated, usually, only by another force which is fiercer. On a historical scale, the global dominance of the Occident itself must be understood as a function of the capacity of the Westerners to impose themselves through violence .
On the other side, according to the Canadian anthropologist Peter Frost, the fall and the conquest of the Roman Empire happened because of the pacification of the most Rome’s population, which had lived in luxury and laziness for a couple of centuries, so that it would not be able, eventually, to resist the blows of extremely aggressive barbarian hoards. The bravest Romans were being recruited in the professional army and they often died without leaving offspring in Roma; instead, many weak, lazy and peaceful individuals stayed in towns, individuals who had promoted the culture of subordination and pacifism. The genes of these people had a larger distribution, as well as their habits.
Thus, in a couple of centuries, somehow paradoxically for a Rome that had conquered the world through boldness and sword, the number of the Romans who were used to a life which was dependent on luxury and non-violence has essentially exceeded the number of the Romans that had a combative spirit. There took place something that Frost terms as “genetic pacification” of a population – a phenomenon that proved to be fatal for the empire in the conditions of foreign invasions [Frost, 2010].
With all the vulnerabilities that Frost’s theory contains, the emphasis that the author lays on the defensive state of a nation is interesting. Non-violence, as a spirit and tradition, besides being very useful for the development of a society in times of stability, proved to be a handicap during a crisis, in a period when violence equals success.
Thanks to the communities, the nations and the states that showed a combative character and got engaged in endless fights, violence and aggressiveness remained, as behavioral states, up to now; the aggression stepped from prehistory into history. The American sociologist Charles Tilly has argued, in his writings, that “war made the state, and the state made war” and that the aggression is the only way in which a nation can survive and perpetuate itself throughout history. These states and nations, which were capable of developing and sustaining great armies, have dominated on a geopolitical level, while the weakly militarized nations, as well as the ones with a low demography, were conquered and destroyed or absorbed by the others [Tilly, 1985].
In this context, I shall also mention that, according to some researchers from the field of national history, like Eric Hobsbawm, the capacity to conquer is one of the three basic criteria that allow a nation to become and to consider itself a nation [Hobsbawm, 1997, p. 41]. In the works of the Romanian historian Nicolae Iorga, we could find the following sententious statement: „At the core of all actions and manners of the old state is the remembrance of the conquest.“
In political sciences, the so-called Just War Theory, the theory which states that violence is a „necessary evil“ and that it represents an immuable reality of history, is quite influently. At their extremes, the idylic pacifism and the roaring militarism would be much more ephemere conditions in the millenial history of humanity .
This variety of aggression‘s expressions in history – from pacifism to militarism -, is nothing more than a gradation of the manifestation of a behavioral phenomenon that is as lively as possible and that does never really disappear, but which can only be partially and temporary shaped and moderated, under the influence of the social context. However, there is something important which has to be observed and that is the fact that, sooner or later, the aggression breaks out.
© Dorian Furtună, ethologist
Photo: Romans / Flickr / https://www.flickr.com/photos/duncanh1/4123999205Dikerogammarus villosus // http://en.wikipedia.org/wiki/Dikerogammarus_villosus
1. Dikerogammarus villosus // http://en.wikipedia.org/wiki/Dikerogammarus_villosus
2. Why Violence Works // By Benjamin Ginsberg. The Chronicle of Higher Education. August 12, 2013 / http://chronicle.com/article/Why-Violence-Works/140951/
3. Just war theory // http://en.wikipedia.org/wiki/Just_war_theory
• Buss D.M., Duntley J.D. Murder by Design: The Evolution of Homicide // Behavioral and Brain Sciences. 2002 / http://www.philosophy.dept.shef.ac.uk/AHRB-Project/Papers/Non-pdf-papers/Buss.html
• Buss D.M., Shackelford T.K. Human aggression in evolutionary psychological perspective // Clinical Psychology Review. Vol. 17. 1997. P. 605-619.
• Duntley J.D., Buss D.M. Homicide adaptations // Aggression and Violent Behavior. Vol. 16. 2011. P. 399-410.
• Frost P. The Roman State and Genetic Pacification // Evolutionary Psychology. Vol. 8(3). 2010. P. 376-389.
• Goetz A.T. The evolutionary psychology of violence // Psicothema. Vol. 22(1). 2010 Feb. P. 15-21.
• Hobsbawm E. Nations and Nationalism Since 1780: Programme, Myth, Reality. Cambridge University Press. 1991.
• Johnson D.D.P., Weidmann N.B., Cederman L.-E. Fortune Favours the Bold: An Agent-Based Model Reveals Adaptive Advantages of Overconfidence in War // PLoS ONE. Vol. 6(6). e20851. 2011. doi:10.1371/journal.pone.0020851
• Kaufmann H. Definitions and methodology in the study of aggression // Psychol. Bull. 1965. Nr.64. P.351-364.
• Macneil C., Boets P., Lock K., Goethals P.L.M. Potential effects of the invasive ‘killer shrimp’ (Dikerogammarus villosus) on macroinvertebrate assemblages and biomonitoring indices // Freshwater Biology. Vol. 58, Issue 1. January 2013. P. 171-182.
• Tilly Ch. War Making and State Making as Organized Crime. in “Bringing the State Back In”, edited by Peter Evans, Dietrich Rueschemeyer, and Theda Skocpol (Cambridge: Cambridge University Press, 1985). P. 169-191.