Evolutionary Psychology of War

Male coalitional combat has been prevalent throughout human history, as evidenced by hundreds of ethnographies of tribal civilizations worldwide. As a result, warfare is a male-dominated activity. The targeted victims are usually other men. However, women are also frequent victims. Although few battles are started to capture women, getting more copulation is nearly always considered a desirable side effect of defeating an adversary.

The Evolutionary Psychology of War

Tooby and Cosmides (1988) called attention to an often-overlooked point in their excellent analysis of the logic of warfare: the battle is a highly cooperative effort. It could not happen unless men on both sides formed cooperative coalitions. The men must band together and work as a cohesive one. Another fundamental impediment to combat development is that the advantages, in fitness currency, must be sufficiently significant to outweigh the severe hazards of damage and death to those who engage.

War is an enormously expensive endeavour for everyone involved. It is difficult to see why any sane organism, selected to survive and genetically propagate, should actively seek to create conditions of such remarkable personal cost and danger. So, how could evolution have chosen psychological processes that predispose males to such dangers? How can we account for the fact that battles have been started regularly throughout documented human history, and soldiers have been treasured and celebrated by the members of their groups?

Critical Requirements for Adaptations for Coalitional Aggression

Tooby and Cosmides' (1988) evolutionary theory of warfare proposes four critical requirements for the development of adaptations for starting coalitional aggression: Over evolutionary time, the average long-term gain in reproductive resources must be significant enough to exceed the reproductive costs of combat. What kind of reproductive resource might be massive enough? The most plausible possibility is increased sexual availability to females--the resource that places the most significant constraint on male reproduction. Because of women's necessary investment in kids, they are a valuable but finite resource for males.

Because of this gender disparity, women have nothing to gain by fighting for more access to males. Sperm is inexpensive, and there has never been a shortage of males prepared to provide it in the numbers women require for adequate fertilisation. To summarize, males stand to benefit significantly from battle if it leads to a significant increase in sexual availability to women.

Coalition members must think that their group will triumph. This includes believing that one's coalition will win the war and its aggregate resources will be more significant after the aggressive encounter. The risk that each member takes and the value of each member's contribution to the success must be reflected in a proportionate share of the rewards. This is a variant of the cheater-detection criterion for cooperative development.

Men not taking risks by fighting must be barred from receiving victory prizes. Men who take more risks, such as commanders who lead their troops into combat, receive a proportionately higher part of the spoils of war. Similarly, men who significantly contribute to the battle's success receive a correspondingly higher share.

Men who go into war must be shielded from knowing who will survive or die. The coalition members' chances of dying must be dispersed more or less randomly. If you already know you will die, you have nothing to gain by going into the fight. Selection would severely oppose any psychological propensity to fight when death is assured.

Indeed, the "battlefield panic" that prompts some soldiers to defect might result from a psychological process that propels a man away from danger as the chance of death approaches certainty. However, if the danger is shared with others and no one knows who will live and die, selection may favour a psychological propensity to engage in coalitional conflict.

Men Engage in Warfare

Across societies, males join coalitions intending to murder men from rival coalitions. Tribes appear continually at war in certain civilizations, such as the Yanomamo. Women have never been witnessed establishing coalitions to murder other humans in any civilization. These facts may appear apparent and were well recognised before Tooby and Cosmides' (1988) theory of conflict development. However, they remain compatible with this idea and call into doubt competing hypotheses, such as war being an arbitrary social construct.

Men Are More Likely to Assess Their Fighting Ability Spontaneously

If males were more likely than women to engage in violent aggression over the history of human evolution, one would expect men to have developed specific psychological mechanisms that drive them to evaluate the conditions under which it is prudent to engage in a fight. One such process is self-evaluation of one's fighting skills compared to other males. Adam Fox (1997), an evolutionary psychologist, projected that males had developed systems for judging combat skill--specifically, men will assess fighting capacity more frequently than women.

To put these predictions to the test, Fox asked a group of college students how frequently they envisioned the likely outcomes of confrontations involving themselves and others. The gender disparities are stark. Most males reported picturing the likely results of such confrontations at least once a month, with once a week being the most frequent response.

In contrast, most women reported just sometimes envisioning the outcomes of confrontations. Women's most prevalent response was never. These data confirm the assumption that males overestimate their fighting prowess more frequently than women--a probable evolved psychological mechanism meant to determine whether it is beneficial to engage in conflict.

Men Have Adaptations That Facilitate Success in War

There are several recognised sex differences that appear to represent battle adaptations in males. Men outperform women in upper body strength: The average guy has about double women's chest, shoulder, and arm strength. Men outperform women in throwing distance and precision, which would aid battle with rocks or spears. They demonstrate superiority in negotiating unfamiliar terrain. Men are prone to forming same-sex alliances that expressly exclude women.

Indeed, on the night before a military raid, males frequently exclude women from the group to minimise any sexual tensions that may exist within the male coalition. Moreover, one of the most common anxieties of men entering combat is that they would act cowardly, embarrassing themselves in the eyes of their friends.


Warfare, defined as aggression by one cooperative coalition against another, is highly unusual in the animal world. Coalitional violence has been documented in only two animal species: chimps and humans. According to evolutionary theory, men will primarily practise combat, with the significant reproductive advantage being increased sexual availability to women.

This theory is supported by empirical evidence: Men have fought throughout recorded history; sexual access to women appears to be a recurring benefit that flows to war winners; men more than women spontaneously assess their fighting ability relative to others; and men value strong coalition members, brave in the face of danger, and have good fighting abilities. Although further study is required, the available information supports the evolutionary theory of warfare and implies that specialised psychological systems tailored to wage war evolved in males.

Updated on: 20-Apr-2023


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