On the Nature of War: An Evolutionary Perspective

by | Feb 2, 2024 | 0 comments

On the Nature of War: An Evolutionary Perspective

Paulo Finuras,

PhD. Associate Professor & Researcher at ISG – Lisbon Business & Economics School


War and violence have always been part of human societies in such a way that we can say that they exist before cultural differences and not because of them. It is a persistent phenomenon among our species, but it is not a phenomenon that is prevalent or exclusive to human beings, and it tends to be increasingly rare among us.

What are the causes of war, what is it for, and how does it develop among human beings? What kinds of wars do we wage and why do they continue to persist? These are some of the aspects that make up this reflection, which uses the evolutionist lens to understand and explain this phenomenon in an absolute way.

Keywords: defensive and offensive war, evolution, motivations, resources, , warfare

1. The State of War in the World Today

We can say that war between humans is a persistent phenomenon, however, it is not prevalent. Although it has always happened, it does not happen everywhere. But let’s go to the evolutionary origins of War to better understand its function and its origin in our species.

War is, by definition, a state of armed conflict between two or more groups or nations using violence, aggression, and military force to achieve a political or social goal and can arise for a variety of reasons, including territorial disputes, ideological differences, revenge, economic interests, scarcity, or competition for access to resources or territories. Wars can be essentially of four types:

1) State-to-Nation (like the current conflict between Ukraine and Russia);

2) Intra-States/Nations (civil wars type);

3) Extra-States/Nations (such as colonial wars or interventionist wars – e.g. Afghanistan and Iraq, 2003)

4) Between States/Nations and an Organization – e.g. Israel vs Hamas or USA vs Al-Qaeda

Wars, as a rule, result in “negative-sum games” in which all parties lose, as well as significant damage and loss of life, destruction of infrastructure, forced displacement of populations, redrawing of borders, and other social, economic, and political consequences in the short, medium, and long term.

Although war has been a part of human history for thousands of years, and continues to persist, it is less and less prevalent. And what does it mean to say that war is persistent but not prevalent? It means that war is and has always been with us (persistence), but although it persists and, therefore, always happens somewhere in the world, it does not happen everywhere (see Fig.1).

Fig. 1 The World at War until February 2022

Source: Statista, 2023

2. On the origins of the War and the direct consequences

Based on archaeology, the first war is believed to have taken place more than 4,000 years ago (2,700 BC) between Sumer and Elam in the Mesopotamian region, but some researchers believe that there may have been other violent conflicts between groups well before that time.

In most places in the world there is no war (hence the non-prevalence), that is, in most places most of the time there is no war, or conflicts of this type, although some or many people judge otherwise from what they see on television. But these feed on everything that is abnormal or exceptional.

Therefore, although war is indeed a persistent phenomenon in our common evolutionary history, we can consider it a “relatively rare” or “exceptional” event, which is why mortality from war worldwide is currently low (0.1%), when compared, for example, with mortality from homicide (0.9%) or suicide (1.3%), according to the most recent data.[1]

3. On the Role of War from an Evolutionary Perspective

Evolutionary theory suggests that war, like other human phenomena, is not unique to us. There is documented research and records of aggression between various groups of animals and insects in more than 80 species and, in some cases, it reaches incredible violence, as is the case with the war between ants, chimpanzees and wolves. All these forms of warfare have one denominator in common: the struggle for resources (including territory).

In our case, organized and proactive warfare achieves an unprecedented lethality given the capacities of our brain and the instruments created, produced and used in and for war.

Comparative studies with other non-human primates suggest that human forms of intergroup violence (namely, invasions and/or raids) seem to closely resemble the “model of chimpanzee violence and warfare” (van Vugt, 2006, 2009; Wrangham & Glowacki, 2012, 2019). However, in relation to the “chimpanzee model of aggression”, human intergroup relations imply greater risks of violence and proactive (i.e., organized and deliberate) aggression and, simultaneously, deeper cooperation and interdependence, covering a spectrum of violence ranging from deadly battles to murders out of simple revenge and hatred, probably more typical of human beings.

In conclusion, this suggests, in a way, that a biological and evolutionary explanation for human-to-human warfare also needs to be complemented with other cultural evolutionary dynamics that can help us understand and explain the incentive structures that facilitate violence and the coalitionist psychology that characterizes human warfare.

It seems that in some situations we have managed to “escape” nature, but nature has not “escaped” us in many others. The figure below summarizes, from a strictly evolutionary point of view, the main motivations and the fundamental and most common types of wars among human beings. Note that this is an evolutionary and factual perspective of the phenomenon (i.e., its phylogeny and ontogeny), without moral, emotional, or sentimental appreciation of the fact.

Table 1

Main motivations and fundamental and most common types of wars between humans

Absolute Explanations for Understanding the Nature of War Between Humans

The origin of warfare is anchored in the struggle to defend or conquer resources 
Type and motivations for War
 Offensive Type WarfareDefensive-type warfare
Motivation: Absolute resource gainWar conducted for the gain of resources for the groupWar Unleashed in Response to Resource Protection
Relative resource gain
Warfare conducted to gain resources or hinder the ability of the adversary or enemy to reproduce by denying them resourcesWar deemed necessary for the protection of current or future resources

Source: Baseado em Bateson e Martin (2000); Hinde (1970); Thayer (2004); Alexander (1987).

In this reflection, we seek the absolute explanations to try to understand and explain the nature of War between human beings, proposing that it is, essentially, anchored in the struggle to gain and defend resources. Although legitimate, other considerations (including rough explanations) do not fit here in this reflection.

As noted earlier, by definition, war is a state of armed conflict between two or more countries or groups within a country to achieve an objective through the use of force. In fact, as von Clausewitz (1918) put [2]it, “war is the continuity of politics by other means”, which means that politics is practiced with and without blood. When it involves blood, it means war. But what are the causes that trigger this type of conflict?

The common element among all wars is that they are almost exclusively initiated and fought by men. True, not all men are violent. Yet virtually every conceivable form of violence that we know of and that is current (from domestic violence to gang fighting, to torture, from genocides to world conflicts) is, and always has been, overwhelmingly perpetrated by men. So, war remains a “man’s business.”

And, if you think about it, there is no known news or fact in our history that a group of women ever invaded a rival village, killed all the women in that village, and raped the men. Has this ever happened? If so, again, it was only committed by men.

Where, then, does this greater propensity of men for violence and war come from? Why are men, for example, the first perpetrators of violent homicides and also the first victims of them? Why is it that men are the ones who contribute to more than 90% of criminal behaviour of all kinds and everywhere, and are they also the ones who die the most in wars today? According to credible sources, for every 100 female servicemen wounded in action during the Iraq War, 5,098 military men were wounded, and for every 100 women who died in combat in Iraq and Afghanistan, 4,102 men died[3]. What could be behind this?

Knowing the root and origins of violence in general and war in particular should lead us to seek absolute answers, not only to their nature, but also to the reasons why human beings, and men in particular, are willing to wage wars, knowing that whatever their outcome, mathematically speaking,  It’s unintelligent, since it can only generate negative-sum results, even for the eventual “winner.”

Why, then, do men make war?

It is well known that wars and armed conflicts have been a part of human history for thousands of years, and have become increasingly destructive as our intelligence has developed more and more of the technologies that support it. But it is also true that wars tend to decrease in the number of occurrences and become an exception in our history.

When we examine the proximate causes of wars, we find that we hardly find a single cause, but several, which are usually interwoven in complicated ways. Among the main theorizations about the proximate origins of wars, we have:

1) the pursuit of territorial gains or competition for resources; 2) the search for economic gains and/or advantages; 3) religious causes; 4) nationalisms; 5) revenge; 6) revolutions; 7) internal civil conflicts; and 8) defensive wars in the preventive form.

Moreover, world history is replete with evidence and examples of each of these types of large-scale wars and their proximate causes as well.

The latter type of war, however, i.e., war waged allegedly for “defensive” reasons and waged in a “preemptive” manner, is one of the most recent and perhaps the most worrying forms.

In today’s world, any state can claim that it is fighting for defensive issues or a threat to its existential security, even for something still in a potential state, and in this way legitimize its action (examples of the invasion and war in Iraq in 2003 or the current Russia-Ukraine conflict).

Based on archaeology, the first war is believed to have taken place more than 4,000 years ago (more precisely, in 2,700 BC) between Sumer and Elam, in the region of Mesopotamia, but there are researchers who believe that other conflicts may have occurred long before that time.

For researcher and political scientist Christopher Blattman (2022), among the main reasons for a war to break out are i) the inability of States to enforce and monitor compliance with agreements; (ii) uncertainty as to the intentions or determination of a party; (iii) uncontrolled or unlimited interests; (iv) misperceptions or miscommunication; and v) other motives for struggle that are intangible, such as nationalism, but which can nevertheless be strongly mobilizing.

As for the deepest and most absolute reasons for wars and why they are dominated and fought essentially by men, well, there the question is relatively more complex (and simpler at the same time).

But a simple, short and provocative answer will be that the ultimate or absolute cause that moves men and leads them to make war is, and always has been… sex.

Yes, it’s more complicated than it sounds.


Alexander, R. (1987). The biology of moral systems. New York: Aldine de Gruyter.

Bateson, P., & Martin, P. (2000). Design for a life: How biology and psychology shape human behavior. New York: Simon and Schuster.

Blattman, C. (2022). Why we fight? London: Penguin Random House.

Hinde, R. (1970). Animal behavior. New York: McGraw-Hill.

Thayer, B. (2004). Darwin and international relations. On the evolutionary origins of war and ethnic conflict. Lexington: The University Press of Kentucky.

van Vugt, M. (2006). Gender differences in cooperation and competition: The male-warrior hypothesis. Psychological Science, 18(1), 19-23. https://doi.org/10.1111/j.1467-9280.2007.01842.x.

van Vugt, M. (2009). Sex differences in intergroup competition, aggression, and warfare: The male warrior hypothesis. Annals of the New York Academy of Sciences, 1167, 124-34. https://doi.org/10.1111/j.1749-6632.2009.04539.x.

von Clausewitz, C. (1918). On war (Col. J. J. Graham, Trans.) (Vol. 1). London: Kegan Paul, Trench, Trubner 

Wrangham, R. (2019). The goodness paradox: The strange relationship between virtue and violence in human evolution. New York: Pantheon.

Wrangham, R., & Glowacki, L. (2012). Intergroup aggression in chimpanzees and war in nomadic hunter-gatherers: Evaluating the chimpanzee model. Human Nature, 23, 5-29. https://doi.org/10.1007/s12110-012-9132-1.


[1] Source: Deaths from self-harm per 100 thousand people – Global Burden of Disease – Institute for Health Metrics and Evaluation (IHME); Suicide — Our World In Data; – WHO – “Preventing suicide: A global imperative”.

[2] Chapter I of Volume 1: What is war? [What Is War] contains Clausewitz’s famous statement about war, according to which it is “the continuation of politics by other means,” and that “[…] War is not merely a political act, but also a real political instrument, a continuation of political commerce, a realization of it by other means. […] the political vision is the object, the war is the means, and the means must always include the object in our conception […]”.

[3] Sources: National Center for Health Statistics, Cited by the author Tomas Mortenson e Congressional Research Service; ScienceDaily; Bureau of Labor Statistics; Census Bureau.


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