A Chimpanzee Civil War: The Inner Demons and Better Angels of Primate Nature

               Ngogo Chimpanzees from the Western Group Attacking the Central Group

As I have indicated in previous posts, evolutionary anthropologists studying the evolution of war and peace have been divided into Hobbesians who believe that our hunter-gatherer ancestors were naturally violent and warlike and Rousseauans who believe that hunter-gatherers were naturally peaceful.  But in setting up this debate as Hobbes versus Rousseau, they have overlooked the position of Locke.  This is a serious mistake, because the weight of the evidence and argumentation on this issue today is on the side of Locke's account of the state of nature as a state of peace that tended to become a state of war.  It seems now that while Hobbes was partly right and partly wrong about the state of nature, Rousseau was mostly wrong, and Locke was mostly right.

THE GOMBE CHIMPANZEES

I have also indicated, how this debate extends to chimpanzees.  The Hobbesians see chimpanzees as showing an evolved propensity to war, and the clearest evidence for this is the chimpanzee civil war that Jane Goodall observed in Gombe in the 1970s.  At the beginning of 1973, she and her colleagues noticed that the chimps had formed two separate communities--the northern or Kasakela community, based on the valleys of the Kakombe and Kasakela rivers, and the southern or Kahama community, based on the valley of the Kahama river.  By early 1974, they saw the first of a series of attacks by the Kasakela community on the Kahama community, which led over four years to the complete annihilation of the Kahama community, which allowed the Kasakela chimps to expand their territory over the area once claimed by the Kahama chimps.  Since human beings are closely related to chimps phylogenetically--chimps and humans evolved from a shared common ancestor some 5-6 million years ago--chimpanzee war could show the evolutionary roots of the human propensity to war.

But the Rousseauans insist that in normal circumstances, chimpanzees are naturally peaceful, and they explain the Four-Year War in Gombe as provoked by the abnormal circumstances created by human impacts on the chimps--particularly, their being fed bananas at Goodall's camp.  During her first two years at Gombe, Goodall was frustrated by her failure to closely observe the chimps because if she attempted to follow them, they ran away from her.  She spent a lot of her time sitting on a hill trying to see the chimps through binoculars.  But then in the summer of 1962, she discovered that if she set out bananas every day, the chimps would crowd into her camp.  Soon they were eating 30, 40, or even 60 bananas per day.

Fighting over the bananas caused increased aggression among the chimps.  They even threw rocks at humans who got too close.  Goodall was shocked by the violence that came from competition for bananas.  Eventually, she tried to lower the violence by restricting the supply of bananas.  This did reduce the violence.  But it also drastically reduced the nutritional benefits that the chimps had gained from the bananas.  Some of Goodall's Rousseauan critics--particularly, R. Brian Ferguson (2023)--have argued that the restriction of the banana feeding created the frustration that prompted the violence of the Four Year War.  When Kasakela males sought food in the southern areas of their range, Kahama males chased them away.  But when Kahama chimps came into Goodall's camp, they were always fed bananas.  So it's not surprising that the Kasakela chimps developed a deep animosity toward the Kahama chimps, although they had once belonged to the same community.

THE NGOGO CHIMPANZEES

Now we have a new report--in the journal Science--of a long-running chimpanzee civil war that has divided the Ngogo chimpanzees in the Kibale National Park in Uganda (Sandel et al. 2026).  The scientists who have studied this group since 1995 have never fed them bananas or any other food.  So artificial provisioning cannot be a factor in explaining their violence.

The Ngogo group is the largest group of chimpanzees ever studied by scientists.  The size has increased from 118 individuals in 1998 to 201 in 2016.  The number of mature males (over 12 years old) has fluctuated around 40 individuals.

The Ngogo chimpanzees range over a large territory, which they have expanded through war with their neighbors.  From 1999 to 2008, they ranged over a territory of about 29 square kilometers (18 square miles).  During this time, they engaged in intensive border patrols, particularly along their northeastern border.  In 2009, they engaged in numerous lethal attacks on their neighbors to the northeast, which allowed them to expand their territory, adding about 6 square kilometers (3.7 square miles) to their territory.  This seemed to confirm the "resource acquisition hypothesis" for explaining chimpanzee warfare as adaptive for territorial expansion (Mitani, Watts, and Amsler 2010).

Prior to 2015, the Ngogo chimpanzees belonged to a single group, although there was a social substructure of two to four "clusters" that could be identified each year.  They were generally divided into a Western cluster and a Central cluster, but this cluster membership was fluid, because individuals could move freely between these clusters.  But then on June 24, 2015, when members of the Western and Central clusters approached each other near the center of their territory, the Western chimpanzees ran away, and the Central chimpanzees chased them.  For at least six weeks, the two groups avoided one another, which had never previously been observed.

In 2016, the Western males started territorial patrols directed toward the Central chimpanzees.  In 2017, what was once the center of a shared territory became a border.  In 2018, the Western group initiated lethal attacks on the Central group.  These aggressive attacks by the Western group have continued up to the present.  Remarkably, the Western group is smaller than the Central group.  In 2018, the Western group had a population of 83 (including 10 adult males and 22 adult females), while the Central group had a population of 107 (including 30 adult males and 39 adult females).  The death toll from the war drove the population of the Central group down to 80 in 2024.

This Ngogo civil war differs from the Gombe civil war in one striking way.  At Gombe, the larger group (the Kasakela chimps) attacked and defeated the smaller group (the Kahama chimps).  This led some primatologists like Richard Wrangham to develop the "imbalance-of-power hypothesis"--that larger groups (particularly, in the number of adult males) will attack smaller groups.  The Ngogo civil war is evidence against that hypothesis.

Actually, the scientists who have studied the Ngogo civil war have not been able to agree on any alternative hypothesis for explaining the war.  Some of them have wondered, however, whether shifting social bonds could explain the rupture that led to the war.  In 2014, five adult males died, perhaps because of disease.  Dr. Aaron Sandel, one of the leaders of the Ngogo Chimpanzee Project, has suggested that these five individuals might have been social bridges that held the Ngogo groups together into one community.  So that the contingency of their deaths in one year created the conditions for the polarization of the community that then led to the war.

Similarly, if Abraham Lincoln had died before or shortly after the beginning of the American Civil War, the history of that war would probably have been radically altered.  Or if Thomas Crooks had assassinated Donald Trump on July 13, 2024, American politics might be very different from what it is today.  America might be less polarized.  And perhaps there would have been no war with Iran.  Such unpredictable contingencies often determine the history of war and politics.

INNER DEMONS, BETTER ANGELS, AND LOCKEAN LIBERAL NICHE CONSTRUCTION

So what, if anything, does the history of chimpanzee wars teach us about the evolutionary history of human war and peace?  How we answer that question may depend a lot on whether we think humans are more closely related to chimpanzees or to bonobos.

Chimpanzees seem to be far more aggressive and violent than are bonobos.  Male chimps attack females and other males.  Sometimes these attacks are lethal.  Male chimps also form coalitions with other males to assert a male dominance hierarchy over females and other males.  These male coalitions also patrol the borders of their community, and they can launch attacks against other communities--even to the point of annihilating the whole community in war.

By contrast, bonobos have never been observed to engage in lethal attacks on other bonobos. Female bonobos seem to be dominant over males.  And the females form coalitions with one another to attack males and mediate their conflicts.  In contrast to chimps, bonobo communities have never been observed to go to war with one another.  Bonobos from different communities can interact with one another peacefully.  All of this peacemaking depends on mutually pleasurable bisexual lovemaking--rubbing their genitals together--females with other females and with males.  This is why the bonobos have been dubbed the "hippie apes" who "make love not war."

Comparing human beings with these two ape species in working out the evolutionary links between the three species has provoked a debate among evolutionary biologists and social scientists.  The Hobbesian scientists argue that human beings are closer to chimps, which shows that the human state of nature was a state of war.  The Rousseauean scientists argue that human beings are closer to bonobos, which shows that the human state of nature was a state of peace.

In my posts on bonobos and the human state of nature, I have argued that Locke's account of the state of nature is closer to the truth than either Hobbes' or Rousseau's, and that evolved human nature combines the natural propensities of both chimps and bonobos.  As Steven Pinker would say, our human nature has both Inner Demons and Better Angels.  Lockean liberalism constructs a cultural niche of social institutions, mental attitudes, and moral traditions that tame the Inner Demons while eliciting the Better Angels to motivate voluntary cooperation and nonviolent relationships.

But in contrasting bonobos and chimpanzees, we should not assume that bonobos are utterly peaceful.  That bonobos are often aggressive in their attacks on one another is made clear in new research by Maud Mouginot and her colleagues (Mouginot et al. 2024).

The message from this study as reported in the press--as in Carl Zimmer's report for the New York Times--is that "male bonobos commit acts of aggression nearly three times as often as male chimpanzees do."  That would seem to deny the common view that chimps are far more aggressive than bonobos.  But if you read the article carefully, you will see that the story is much more complicated than that.

Mouginot and her colleagues employed what scientists studying animal behavior call the "focal-animal sampling" method (Altman 1974).  All occurrences of specified actions of an individual, or specified group of individuals, are recorded for a pre-determined period of time.  

For their study, they had all-day focal follow data for 14 chimpanzee adult males from two communities in the Gombe National Park in Tanzania and 12 bonobo adult males from three communities in the Kokolopori Bonobo Reserve in the Democratic Republic of the Congo.  They had recorded hundreds of aggressive dyadic interactions, including contact aggression (physical contact such as hit, pull, bite, kick, or jump-on) and non-contact aggression (such as charge and chase).  They had also recorded whether the focal-male was the aggressor or the victim and whether he was interacting with another male or with a female. 

They wanted to use this data to test the "self-domestication hypothesis" of Brian Hare and Richard Wrangham, who have suggested that bonobos evolved to be less aggressive than chimpanzees just as dogs evolved to be less aggressive than wolves.  Humans selected less aggressive (or friendlier) wolves to become their companions, and over time, wolves evolved into dogs through domestication by human selection.  Similarly, if female bonobos formed coalitions to punish aggressive males, and if females preferred to mate with less aggressive males, which would tend to produce less aggressive offspring, bonobos could have been self-domesticated for being less aggressive or friendlier to one another (Hare, Wobber, and Wrangham 2012).

Moreover, Hare and Wrangham have also suggested that humans could have undergone a similar process of evolution by self-domestication to be less aggressive or friendlier towards individuals within their community (Hare 2017; Hare and Woods 2020; Wrangham 2019).  I have extended this idea of human self-domestication to explain the evolution of Lockean liberalism and the bourgeois virtues as symbolic niche-construction.

What Mouginot and her colleagues have found does not deny the self-domestication hypothesis of Hare and Wrangham, although it might require some refinement in the theory.  They found that there was a higher rate of male-male contact aggression among bonobos than chimpanzees.  And in both species, the more aggressive males had higher mating success.  But they found no evidence to contradict the observation that bonobos never kill other bonobos, while chimpanzees do kill other chimpanzees in fighting both within and between communities.

One possible explanation for why bonobo males engage in more non-lethal aggression with other males than do chimpanzee males is that since bonobo females prevent males from forming coalitions, bonobo males can attack other males without suffering reprisals from male coalitions.

As Hare told Carl Zimmer, the one dramatic difference in aggressiveness between the two species remains:  "Chimpanzees murder, and bonobos don't."

Frances White, one of the leading scientists studying bonobos in the wild, has explained that in the wild bonobo females serve a policing function, in that they intervene in fights to moderate conflicts through impartial mediation, because they benefit from living in a stable social order that is not disrupted by violence.

She has also observed that bonobos--like all primates--show a range of personality types, so that some individuals have more violent temperaments than others, and consequently the occurrence of violence can depend on the contingency of whether there are such violent individuals in the group.  She said that many of the deaths of the males comes from "testosterone poisoning"--young males vigorously displaying their virility in the forest canopy can kill themselves by slamming into a tree.

She has also said that if dominant males are grouped together in zoos without females who can moderate their male conflicts, then nasty fighting is likely to break out.  She has explained then that what the females are doing in the wild groups in pacifying conflicts is "niche construction"--behavior that creates a social environment in which stable and peaceful cooperation is adaptive.

In most of evolutionary theory, we think of organisms as carrying genes, and the inheritance of these genes by the next generation depends on organisms surviving and reproducing according to chance and natural selection in their environments.  But there is another process of evolution that arises from organisms changing their environments, which modifies the natural selection pressures in their environments.  This is evolutionary niche construction (Odling-Smee, Laland, and Feldman 2003).  Among many animals, evolutionary niche construction includes the transmission of culturally learned traditions.  And among human beings, it includes the transmission of culturally learned symbolic systems such as art, science, religion, and philosophy.

I have suggested that the history of classical liberalism is evolutionary niche construction, and that this is a big part of Pinker's argument: the history of classical liberal philosophy has created a cultural moral environment of liberalism in which peaceful cooperation and declining violence are adaptive.  (This is what Deirdre McCloskey would identify as the work of rhetorical entrepreneurs in the marketplace of ideas who have used moral persuasion to create a liberal culture that honors the bourgeois virtues.)

As Pinker argues, human nature is a mixture of Inner Demons and Better Angels.  Human beings are innately predisposed to violence by their Inner Demons, but the expression of those predispositions is not "hydraulic"--that is, a drive that must necessarily be satisfied--but "strategic"--that is, a propensity that is responsive to environmental triggers.  Classical liberalism constructs a cultural niche of social institutions, mental attitudes, and moral traditions that tend to elicit the Better Angels to motivate voluntary cooperation and nonviolent relationships.

In this way, human nature constrains and enables but does not determine human culture and individual judgment.  Within the constraints of human nature as a mixture of Inner Demons and Better Angels, classical liberalism can foster those cultural traditions and individual judgments that limit the Inner Demons and channel the Better Angels towards a system of liberty and voluntarism.

REFERENCES

Altman, Jeanne. 1974. "Observational Study of Behavior: Sampling Methods." Behaviour 48: 227-65.

Ferguson, R. Brian. 2023. Chimpanzees, War, and History: Are Men Born to Kill? Oxford, Oxford University Press.

Goodall, Jane. 1986. The Chimpanzees of Gombe. Cambridge: Harvard University Press.

Hare, Brian. 2017. "Survival of the Friendliest: Homo sapiens Evolved via Selection for Prosociality." Annual Review of Psychology 68: 155-86.

Hare, Brian, and Vanessa Woods.  2020.  Survival of the Friendliest: Understanding Our Origins and Rediscovering Our Common Humanity. New York: Random House.

Hare, Brian, V. Wobber, and Richard Wrangham.  2012.  "The Self-Domestication Hypothesis: Evolution of Bonobo Psychology Is Due to Selection Against Aggression."  Animal Behaviour 83: 573-85.

Mitani, John C., David P. Watts, and Sylvia J. Amsler. 2010. "Lethal Intergroup Aggression Leads to Territorial Expansion in Wild Chimpanzees." Current Biology 20:R507-R508.

Odling-Smee, F., Kevin Laland, and Marcus Feldman. 2003. Niche Construction: The Neglected Process in Evolution. Princeton University Press.

Pinker, Steven. 2011. The Better Angels of Our Nature: Why Violence Has Declined. New York: Penguin Books.

Sandel, Aaron A. et al. 2026. "Lethal Conflict After Group Fission in Wild Chimpanzees." Science 392(9 April):216-220.

Wrangham, Richard.  2019.  The Goodness Paradox: The Strange Relationship Between Virtue and Violence in Human Evolution.  New York: Pantheon Books.

Zimmer, Carl.  2024.  "No 'Hippie Ape':  Bonobos Are Often Aggressive, Study Finds." The New York Times, April 12.

The Behavioral Ecology of Chimpanzee War and Liberal Peace

I have argued that if political science ever becomes a science, it will be a biopolitical science of political animals.  An important part of such a biopolitical science would be the behavioral ecology of war and peace among human beings, chimpanzees, and other political animals.

Behavioral ecology is the study of animal behavior as shaped by evolution for adaptive responses to ecological conditions so as to increase the probability that animals will survive and reproduce.  If those ecological conditions are fixed and predictable, then evolution will favor rigid behavioral responses to those conditions that are adaptive.  But if those ecological conditions are changeable and unpredictable, then evolution will favor flexible behavioral responses based on gathering and assessing information about the costs and benefits of alternative strategies of behavior.  For social and political animals, the most important features of their ecology are other members of their species, whose behavior is changeable and unpredictable.  Consequently, their brains and nervous systems are adapted for making social judgments about the contingencies of their social environment.

Thus, in competing with other animals for access to scarce resources (like mates, food, or territory), they will decide to fight only when the likely benefits outweigh the likely costs.  A species will have an evolved propensity to warfare, therefore, only if in its ancient environment of evolutionary adaptation, lethal attacks by one group on another could under some conditions enhance the inclusive fitness of the attacking group.  But even if a species has such an evolved propensity to warfare, war is not inevitable, because the behavioral flexibility of these animals can be such that they will not engage in lethal fighting in conditions where the likely costs of such fighting outweigh the likely benefits.

So we should be able to decide the debate over whether warfare is a natural adaptation for human beings, chimpanzees, and other political animals by seeing if there is evidence of warfare in their ancient evolutionary history.  The problem, however, is that the most prominent scientists in this debate seem to interpret the evidence in opposing ways as conforming to one of two opposing intellectual frameworks--the Hobbesian view or the Rousseauean view.

As suggested by Thomas Sowell's A Conflict of Visions, much of the social thought of the past three centuries shows a contrast between a "constrained vision" and an "unconstrained vision" of social life, which I call the "realist vision" and the "utopian vision."  Those with the realist vision of life believe that since the moral and intellectual limits of human beings are rooted in an unchanging human nature, a good social order must make the best of these natural limitations rather than trying to change them.  But those with the utopian vision of life believe that since the moral and intellectual limits of human beings are rooted in social customs and institutions that are changeable, the best social order would arise from rationally planned reforms in these customs and institutions that would perfect human nature.  On the side of the realist vision, Sowell places thinkers like Thomas Hobbes, Edmund Burke, Adam Smith, and Friedrich Hayek.  On the side of the utopian vision, he places thinkers such as Jean Jacques Rousseau, William Godwin, Thomas Paine, and John Rawls. 

This conflict of visions is manifest in the debate over the evolution of war among chimpanzees.  Those scientists who insist that warfare is not a natural adaptation for chimpanzees are criticized by their opponents as Rousseaueans, who naively ignore the harsh reality of chimpanzee warfare.  And those scientists who insist that warfare is a natural adaptation for chimpanzees are criticized by their opponents as Hobbesians, who cynically defend the image of the "killer ape" against the evidence of chimp peacemaking.

Prior to 1960, when Jane Goodall began the first long-term study of chimpanzees in the wild, there was not enough evidence to resolve this debate, because of the lack of precise observation of chimpanzee politics.  Now, however, we have had many decades of studying wild chimpanzees at many different sites in Africa.  We have also had many studies of chimpanzees in captivity by people like Frans de Waal and Michael Tomasello, which are studies that more easily lend themselves to experimental research than is typically the case for studies in the wild.

One serious limitation in studies of captive chimpanzees is that the observer has no chance to see warfare, since the closed environment of captivity does not give the chimps enough room to divide up into groups that might engage in warfare.  Even in the wild, however, it's hard to see chimp warfare. 

Throughout the 1960s, Goodall reported on how peaceful the chimps were in what is now Gombe National Park in Tanzania, and thus she confirmed the common view that human beings were the only animals that deliberately killed members of their own species in war.  Beginning with her first article in National Geographic in August of 1963--"My Life Among Wild Chimpanzees"--Goodall became one of the world's most famous naturalists, a heroic young woman whose adventures with wild chimpanzees took on mythic proportions.  But then, in the early 1970s, she shocked the world with her reports of brutal chimp warfare.

 

  

By the beginning of 1973, Goodall recognized that her community of chimpanzees had split into two separate communities--the northern or Kasakela community and the southern or Kahama community.  By early 1974, she saw the first of a series of violent attacks against members of the Kahama community by Kasakela males moving southward into the Kahama community range.  By the end of 1977, the Kahama community had been annihilated, and the Kahama territory was annexed into the Kasekela territory.

Adult males of the Kasakela community seemed to be raiding the territory of Kahama.  When these Kasakela males found isolated Kahama individuals, they used their numerical superiority to brutally kill these individuals without any injury to the attackers.  The killing was similar to what chimpanzees do in hunting other animals, so it was as though the chimpanzee victims had been "dechimpized" by the chimpanzee killers.

In The Chimpanzees of Gombe (1986), Goodall suggested that chimpanzee warfare showed the primate precursors of human warfare:  "The chimpanzee, as a result of a unique combination of strong affiliative bonds between adult males on the one hand and an unusually hostile and violently aggressive attitude toward nongroup individuals on the other, has clearly reached a stage where he stands at the very threshold of human achievement in destruction, cruelty, and planned intergroup conflict" (534).

Goodall and others in her research team worried, however, that their artificial feeding of the chimpanzees had disrupted their behavior in ways that might cast doubt on whether the behavior they were observing was typical for chimpanzees in the wild.  Goodall had discovered during her early years that the animals were so wary of her that the only way she could observe them and photograph them was to feed them bananas.  Only in later years did the animals become so habituated to human presence that they could be observed without artificial feeding.

I remember in 1986 attending a conference on chimpanzee and bonobo studies in Chicago sponsored by the Chicago Academy of Sciences.  Most of the leading researchers were there, including Goodall.  I noticed that in many of the films shown by the speakers, the animals were being fed bananas or sugar cane by the human observers.  In one of the question-and-answer sessions, I asked one of the speakers about whether this artificial feeding might distort the behavior of the animals.  Some of the speakers became visibly agitated by my question, and some of them claimed that they had stopped the artificial feeding at their sites.

In 1991, Margaret Power's book The Egalitarians--Human and Chimpanzee argued that both humans and chimpanzees were peaceful egalitarians by nature in their original condition as hunter-gatherers.  She insisted that the apparently aggressive, warlike, and hierarchical behavior of the chimps observed by Goodall and others was produced by the human disruption of artificial feeding.  When chimps crowd around the food, they have to fight and form dominance hierarchies in ways that would not occur without the artificial feeding.  By contrast with provisioned chimps, she argued, wild chimps are like human hunter-gatherers in being "Rousseauean foragers" who live in a "mutual dependence system" in which all individuals cooperate peacefully and generously as equals acting for the common good of all, and thus they conform to Rousseau's theory of the best social order, in contrast to the common assumption in Western culture that inequality and war are natural.

When William McGrew wrote an review of Power's book for Nature (November 28, 1991), it was entitled "Apes Cast Out of Eden?"  He accused her of forcing chimpanzees into a utopian Rousseauean model.  He admitted that artificial provisioning was a dubious technique.  But he argued that research at sites in Africa where chimps were not artificially provisioned had confirmed Goodall's observations.  And thus it was unlikely that artificial feeding had brought about "the Fall that cast out the apes from their equatorial Garden of Eden."  He concluded that "we must face up to the fact that chimpanzees are probably very like us, warts and all."

In 1996, Richard Wrangham and Dale Peterson in Demonic Males: Apes and the Origins of Human Violence elaborated Goodall's suggestion that human violence and war were rooted in an evolutionary history shared with chimpanzees.  They argued that humans and chimpanzees share in a unique combination of social traits, in having male-bonded communities in which coalitions of males engaged in lethal raiding against outside groups.  They developed an "imbalance of power theory" for the evolution of warfare:  adult males will engage in coalitionary attacks against other groups when they can surprise isolated members of the other group, so that the attackers can injure or kill their victims to gain valuable resources (access to food, mates, and territory) without the attackers risking any injury to themselves.  Thus, for the attackers, the benefits of fighting outweigh the costs, with costs and benefits measured in terms of survival and reproductive fitness.

In their first chapter--entitled "Paradise Lost"--Wrangham and Peterson described the blissful image of wild chimpanzees conveyed by Gooodall during the first decade of her observations: "Wild chimpanzees in the dappled forest teaching and learning, playing, communicating with invented signals, doctoring themselves, using tools to enrich their food supply.  These scenes conjure classic visions of a peace in nature, an Eden of prehistory. . . . Like a rich fantasy of Jean Jacques Rousseau . . . . The apes seemed to wander without boundaries, with no fear of strangers.  Sex was public, promiscuous, and unprovocative.  There was little fighting over food" (11). 

But then, shortly after Wrangham first arrived at Gombe in 1970 as a zoology graduate student, the rift in the chimpanzee group and the eventual annihilation of the Kahama community exposed the dark side of chimpanzee life, which also exposed the dark evolutionary origins of the human natural propensity to violence and war as rooted in the aggressive temperament of "demonic males."  When many anthropologists refuse to believe that such aggression among chimpanzees and humans has deep evolutionary roots, Wrangham observes, they show their deep yearning for Rousseau's noble savage and their Rousseauean commitment to the thought that human evil is culturally acquired and thus not a natural adaptation.

Charged with showing a stubborn Rousseauean bias that distorts their view of the evidence, the proponents of peaceful egalitarianism as natural for both humans and chimps respond by charging their opponents with showing a Hobbesian bias.  As I have indicated in an earlier post, that's the response of those like Marshall Sahlins and Douglas Fry.  So here again we see Sowell's conflict of visions.

We might hope that with more study of chimpanzee behavior, we might eventually have enough evidence to resolve this conflict over the evolution of war and peace among chimpanzees.  The best recent survey of that evidence that I have seen is a chapter in War, Peace, and Human Nature edited by Douglas Fry--Michael Wilson's "Chimpanzees, Warfare, and the Invention of Peace."  Wilson opens his chapter by framing the debate as a dispute between the intellectual traditions associated with Hobbes and Rousseau--Hobbesians asserting that warfare is a natural adaptation and Rousseaueans asserting that it is a cultural invention.  Wilson is an evolutionary anthropologist at the University of Minnesota who specializes in the study of chimpanzee conflict.  Having worked with Wrangham, Wilson is clearly on the Hobbesian side of the debate in arguing that war is a natural adaptation, and peace is a cultural invention.

Most of the contributors to Fry's book are on the Rousseauean side, and so comparing what they say with Wilson's chapter allows one to judge the strength of Wilson's case.  If one does that, I think one has to conclude that the evidence supports Wilson's position.  But one also has to conclude that the Hobbesians and Rousseaueans are more in agreement than they realize.

The first point of agreement is that violent aggression among humans and chimps is a flexible natural propensity that tends to be stronger in males than in females, and the expression of that propensity depends on the social circumstances that determine the relative costs and benefits of violent fighting.  So, for example, Fry, David Barash, Robert Sussman, and Wilson all seem to agree on this (35-37, 104, 108, 451, 455-56, 467).  As Fry says in Beyond War, violent aggression is a "flexible, or facultative, adaptation" of males rather than a "fixed, or obligate, adaptation," and thus its expression depends on environmental conditions (173-74).  Wilson stresses that viewing adaptive violence through behavioral ecology highlights the fact that the expression of violence depends on the social circumstances (362-64, 381).  Thus, he agrees with Azar Gat that war is "innate but optional."

The second point of agreement is that the social life of humans and chimps is mostly peaceful, because they have evolved capacities for cooperating peacefully and reconciling conflicts.  It took Goodall over ten years before she observed lethal violence among her chimps.  Similarly, most human beings live out their lives without directly observing homicidal violence.  We can all agree with Fry that "in societies around the world, most disputes are resolved without any violence at all" (545).  This is also true for chimps, because, as Wrangham and Peterson observed, "chimpanzees lead very peaceful lives" (11).

The third point of agreement is that we can use our evolutionary understanding of war and peace among chimps and humans to promote the cultural conditions for peace.  We can see that the formation of states that enforce legal codes can pacify conflict by establishing the governmental punishment of aggressors.  We can also see how global institutions and global networks of trade can raise the costs of war and the benefits of peace so that warfare is unattractive.  Wilson observes that human beings differ from chimps in that "chimpanzees have nothing to trade with their neighbors," while human beings can use trade to turn intergroup interactions into a nonzero-sum game rather than a zero-sum game, which contributes to what is now called the liberal or democratic peace (381-82).  This confirms Adam Smith's claim about the human uniqueness of the "propensity to truck, barter, and exchange," and how this allows human beings to expand the gains from trade.

So where's the disagreement over Wilson's view of chimpanzee warfare?  Some of the Rousseaueans repeat Power's argument that chimpanzees as "Rousseauean foragers" have been transformed into Hobbesian animals by artificial feeding.  But as Wilson indicates, this cannot be true, because extensive study of chimpanzees at many sites in Africa where there has been no artificial feeding confirm Goodall's earlier observations (376-78).

Sussman argues that it is not just food provisioning that is disruptive but stress caused by all kinds of human impact--"habitat loss, snare poaching and hunting, epidemics, demographic disruption, impacts of research and tourism, and so on" (104).  Wilson's responds to this by claiming that if one compares chimpanzee study sites across Africa, estimates of human disturbance do not explain much of the variation in rates of lethal violence (378).  Here he cites a recent conference paper that he coauthored with others, which I have not yet read.

Sussman also argues that killing among chimpanzees is too infrequent for it to be an evolved adaptation.  He calculates that the reports from the long-term research sites show a rate of only one chimpanzee killing every 7.5 years (104).  Wilson's response to this is to argue that the frequency of killing is not a measure of its evolutionary importance.  Moreover, Wilson indicates, the rate of chimpanzee intraspecific killing is higher than the homicide rate in the United States, when one calculates this as the number of violent deaths per 100,000 individuals per year (370).

And yet, even if the Rousseaueans are forced to agree with Wilson's conclusions about chimpanzee warfare, they can point to bonobos as the true "Rousseauean foragers," whose evolutionary lineage is as close to human beings as is that of the chimpanzees.  The dedication of Fry's book is "To Bonoboess," because Fry thinks female bonobos offer us the best Rousseauean path to peaceful egalitarianism.  Bonobos seem to be peaceful, because they have never been observed engaging in lethal fighting.  Bonobos seem to be egalitarian, because while they have both male and female dominance hierarchies, the females seem to bond with one another to resist male dominance over the females.  Most famously, bonobos use sexual activity, including homosexual activity, to release social tension and promote social bonds.

Immediately after Wilson's chapter in Fry's book, Frances White, Michel Waller, and Klaree Boose have a chapter on "Evolution of Primate Peace" that compares chimpanzees and bonobos.  Frances White is one of the most experienced observers of bonobos.  Like Wilson, White employs a behavioral ecology approach to show how chimpanzees and bonobos differ in their behavioral strategies because they are adapted to differing ecological conditions depending on the importance of monopolizable resources.

Wild bonobos are found only south of the Congo River in the Democratic Republic of the Congo.  White argues that in this area the large size of the food patches lowers the level of feeding competition, which allows a female-bonded social structure.  Greater female-bonded groups constitute a monopolizable resource, and individual males compete for access to these groups.  But there is no advantage for males to cooperate in male coalitions to defend and expand territories containing females.

White suggests that while studying chimpanzee warfare will help us to understand human war, studying bonobos might help us to understand the conditions for peacemaking.  Similarly, Wrangham and Peterson indicate how lessons from the bonobos identify some paths to peace.  We might move from a male-dominated system of power to a sharing of power between men and women, which can be promoted through a feminization of culture and democratic institutions.  We might also promote a world system of moral sanctions favoring peace.  In considering these possibilities, we see that "male demonism is not inevitable" (Demonic Males, 251). 

Here we see the anticipation of Steven Pinker's argument for how a liberal culture promotes a liberal peace by appealing to the "better angels of our nature."  But still this remains within the Hobbesian tradition, because it's a "constrained vision" in which the "better angels" are constrained by the "inner demons" that can be tamed but not abolished.

Some posts on related topics can be found here, here, here, here, here, here, here, and here.

The MPS in the Galapagos (11): Wrangham on the Evolution of War

The question of whether the original state of nature for human beings was a state of war or a state of peace has been a contentious question in political philosophy, beginning with Hobbes, Locke, and Rousseau.  This continues to be one of the most intensely debated questions in the social sciences, with some people adopting the Hobbesian view of the state of nature as a state of war, and others adopting the Rousseauian view of the state of nature as a state of peace.  Most recently, the debate has been renewed in this week's issue of Science with Douglas Fry's defense of the Rousseauian position and attack on Richard Wrangham's Hobbesian position.  Fry's article has drawn a lot of press coverage, including a feature article in The Economist.

As someone who combines interests in the history of political philosophy and Darwinian anthropology, I see this debate as an illustration of how modern empirical research in evolutionary biology can illuminate old disputes in political philosophy.  As I have indicated in some previous posts, early modern political philosophers (from Hobbes to Smith) studied and debated the anthropological reports about the social life of the native Americans as showing the original condition of humanity.  As Locke declared: "In the beginning, all the world was America." 

This shows that political philosophy is an empirical evolutionary science of politics.  Consequently, the serious study of the history of political philosophy must include the study of evolutionary science.  This should be evident when one considers the philosophic implications of the current anthropological debate over the evolution of war and peace.

I was pleased, therefore, by Wrangham's lecture on "Why Evolution Matters for War" at the MPS conference, which allowed me to think more about this debate and its ramifications for political philosophy.  Much of what Wrangham said in his lecture has been elaborated in a recent article in Human Nature that he coauthored with Luke Glowacki.

Wrangham is a Professor of Biological Anthropology in the Department of Human Evolutionary Biology at Harvard University.  (In 2009, the program of Biological Anthropology in the Department of Anthropology at Harvard was reconstituted as a new Department of Human Evolutionary Biology.)  He is the co-director of the Kibale Chimpanzee Project, which is a long-term study of the Kanyawara chimpanzees in Kibale National Park in Uganda.  His book Demonic Males: Apes and the Origins of Human Violence (1996) is a book that I have found useful as a text in some of my political theory classes. 

Here's a general summary of Wrangham's position as stated in the abstract for his article in Human Nature:

"Chimpanzee and hunter-gatherer intergroup aggression differ in important ways, including humans having the ability to form peaceful relationships and alliances among groups.  This paper nevertheless evaluates the hypothesis that intergroup aggression evolved according to the same functional principles in the two species--selection favoring a tendency to kill members of neighboring groups when killing could be carried out safely.  According to this idea, chimpanzees and humans are equally risk-averse when fighting.  When self-sacrificial war practices are found in humans, therefore, they result from cultural systems of reward, punishment, and coercion rather than evolved adaptations to greater risk-taking.  To test this 'chimpanzee model,' we review intergroup fighting in chimpanzees and nomadic hunter-gatherers living with other nomadic hunter-gatherers as neighbors.  Whether humans have evolved specific psychological adaptations for war is unknown, but current evidence suggest that the chimpanzee model is an appropriate starting point for analyzing the biological and cultural evolution of warfare" (5).

Wrangham contrasts his "chimpanzee model" with "human-specific models" and "nonadaptive models" for explaining the evolutionary basis of war.  The "human-specific models" agree with the "chimpanzee model" in seeing war as an evolutionary adaptation, but they see uniquely human psychological propensities to war that are not shared with chimpanzees--such as propensities for taking self-sacrificing risks in war (proposed by Samuel Bowles as "parochial altruism"), tendencies for "strong reciprocity" (Herbert Gintis), or revenge-seeking (Christopher Boehm).

The "nonadaptive models" deny that there has been any evolutionary selection for warfare among prehistoric hunter-gatherers, and consequently warfare has been a purely cultural development of agrarian societies with centralized states and military bureaucracies.  The reasoning for this kind of model is evident in some excerpts from Douglas Fry's article, coauthored with Patrik Soderberg, in Science: 

"It has been argued that warfare evolved as a component of early human behavior within foraging band societies.  We investigated lethal aggression in a sample of 21 mobile forager band societies (MFBS) derived systematically from the standard cross-cultural sample.  We hypothesized on the basis of mobile forager ethnography, that most lethal events would stem from personal disputes rather than coalitionary aggression against other groups (war).  More than half of the lethal aggression events were perpetrated by lone individuals, and almost two-thirds resulted from accidents, interfamilial disputes, within-group executions, or interpersonal motives such as competition over a particular woman.  Overall, the findings suggest that most incidents of lethal aggression among MFBS may be classified as homicides, a few others as feuds, and a minority as war" (270).

"The findings suggest that MFBS are not particularly warlike if the actual circumstances of lethal aggression are examined.  Fifty-five percent of the lethal events involved a sole perpetrator killing only one individual (64% if the atypical Tiwi are removed).  One-person-killing-one-person reflects homicide or manslaughter, not coalitional killings or war.  Additionally, 36% of all lethal events occurred within the same local group (62% if the atypical Tiwi are removed), and violence within a local group is not coalitional war.  Only 15% of the lethal events occurred across societal lines. . . ."

"Approximately half of the societies had no lethal events that involved more than one perpetrator.  This observation is incongruent with assertions by Bowles and Pinker that war is prevalent in MFBS or by Wrangham and Glowaki that humans have an evolved tendency to form coalitions to kill members of neighboring groups. . . ."

"In conclusion, when all cases are examined for a systematically drawn sample of MFBS, most incidents of lethal aggression can aptly be called homicides, a few others feud, and only a minority warfare.  The findings do not lend support to the coalitionary model.  The predictions are substantiated that MFBS, as a social type, possess many features that make warfare unlikely. . . ." (272) 

In response to this kind of argument, Wrangham has identified five weaknesses in Fry's reasoning that are commonly found in "nonadaptive models."

First, Fry fails to distinguish "simple warfare" and "complex warfare," and then he assumes that hunting-gathering societies show no warfare if they don't show complex forms of warfare.  "Simple" warfare is found in small societies without formal political hierarchies, and it consists mostly in raiding and feuding without lethal battles between organized opponents.  "Complex" warfare is found in larger societies with formal political hierarchies where lethal battles are fought by soldiers under the command of leaders.  Chimpanzees and some other animals show "simple" but not "complex" warfare.  When Fry finds little evidence of "complex" warfare among hunter-gatherer societies, he falsely concludes that there is no warfare at all.  So he sees a record of raiding and feuding among hunter-gatherers but refuses to recognize this as war.

The second weakness is that Fry does not distinguish between "internal" and "external" war.  "Internal" war is war among the bands belonging to the same society--the same cultural or linguistic group.  "External" war is war between people of different societies--different cultural or linguistic groups.  Wrangham has argued that while there is no stable pattern to "internal" warfare, there is a stable pattern of hostility in "external" war.  Fry's conclusion that coalitionary killing is not a uniform tendency in internal warfare has no relevance to Wrangham's claim that coalitionary killing is an evolved human tendency in external warfare.

The third weakness is that Fry fails to identify the crucial criteria for determining whether a hunter-gatherer society provides the best model of prehistoric behavior.  A crucial criterion for Wrangham is whether a hunting-gathering society was constrained by neighboring farming societies.  By the time most of these recent hunting-gathering societies were studied, they were bordered by farming societies that could dominate them politically and militarily, and so if the hunter-gatherers had no record of warfare, this could easily be explained as coming from a wise calculation that war was futile.  If one is looking for situations comparable to those faced by our original hunter-gatherer ancestors, one would need to look only at hunter-gatherer societies with neighboring societies of hunter-gatherers.  The anthropological record shows only a few cases like this, including societies in Alaska, Tasmania, Australia, the Andaman Islands, New Guinea, and Tierra del Fuego.  When Wrangham and Glowacki surveyed the record for these societies, they found a universal pattern of warfare.

The fourth weakness in Fry's reasoning is his assumption that proof of hunter-gatherer warfare would require that a high proportion of violent deaths should come from war.  But that does not follow if one agrees with Thomas Hobbes: "For Warre, consisteth not in Battel only, or in the act of fighting, but in a tract of time, wherein the will to contend by Battel is sufficiently known."  Even when hunter-gatherer societies have long periods without high death rates from war, there can still be a perpetual state of hostility and readiness to go to war.

The final weakness in Fry's position is his assumption that affirming the evolutionary roots of war is affirming that war is inevitable and ineradicable, and therefore those (like himself) who deny the evolutionary roots of war are thereby promoting peace.  This is not true, because explaining the evolutionary propensity to war in human nature is not to affirm this as a necessity that cannot be changed.  In fact, understanding war as a natural propensity can be a precondition for understanding how best to promote peace.  That's evident, for example, in Steven Pinker's The Better Angels of Our Nature.  Pinker agrees with Wrangham and others who argue for primitive warfare as an evolutionary adaptation.  But for Pinker (as well as Wrangham), this helps us to understand the conditions required for promoting the modern decline in violence.  We must see how the "inner demons" of our human nature can be overcome through the "better angels" of our nature.

The strange assumption that Fry's position somehow occupies the moral high ground in this debate is manifest in the article by Elizabeth Culotta in the "News & Analysis" section of Science highlighting Fry's article.  She says that Fry's article "strikes a blow for peace," as if Fry's critics were motivated by a love of war, which is clearly a false claim.

It would be instructive if Fry would write a response to Wrangham's criticisms.

If Wrangham is right in his critique of Fry's reasoning, then this would suggest that the evidence now supports the conclusion that Hobbes was right, and Rousseau was wrong.


REFERENCES

"The Origins of War," The Economist,  July 20, 2013, pp. 69-70.

Culotta, Elizabeth, "Latest Skirmish Over Ancestral Violence Strikes Blow for Peace," Science, 341 (19 July 2013): 224.

Fry, Douglas P., and Patrik Soderberg, "Lethal Aggression in Mobile Forager Bands and Implications for the Origins of War," Science, 341 (19 July 2013): 270-73.

Wrangham, Richard W., and Luke Glowacki, "Intergroup Aggression in Chimpanzees and War in Nomadic Hunter-Gatherers: Evaluating the Chimpanzee Model," Human Nature, 23 (2012): 5-29.

Science News has an article on the Wrangham-Fry debate that can be found online.

Some other posts on the evolution of war and peace can be found here, here,  here., here., here, and here.

Gat on War (1): Hunter-Gatherers

Azar Gat's War in Human Civilization (Oxford University Press, 2006) is one of the best scholarly studies of war ever written. He ranges broadly over many disciplines: animal behavior, evolutionary theory, evolutionary psychology, anthropology, archaeology, history, sociology, and political science. Rather than pursuing a reductive explanation of war as determined by one or a few factors, he encompasses all the major factors influencing the whole history of human warfare over two million years, while showing how evolutionary theory can explain the origins and interrelationships of all of these factors.

He sets out to answer the "riddle of war."

Why do people engage in the deadly and destructive activity of fighting? Is it rooted in nature, or is it a late cultural invention? Have people always engaged in fighting, or did they start to do so only with the advent of agriculture, the state, and civilization? How were these, and later, major developments in human history affected by war, and, in turn, how did they affect war? Under what conditions, if at all, can war be eliminated, and is it declining at present? (p. ix)

His massive study (822 pages) of these questions is divided into three parts corresponding to the three great eras of human history: the era of hunter-gatherers, the era of agrarian civilization and pre-modern states, and the era of the modern nation-states. This first post on the book will be on the first part, which covers the history of war over two million years, the period of hunting-gathering, which constitutes over 99 per cent of human history, in which the genetic evolution of the human species was shaped.

This book has helped me to think through the evolution of war as an evolved natural desire. I have included courage in war as one of the twenty natural desires.

Human beings generally desire war when they think it will advance their group in conflicts with other groups. Human beings divide themselves into ethnic and territorial groups, and they tend to cooperate more with those people who belong to their own group than with those outside their group. So when the competition between communities becomes severe, violent conflict is likely. Human beings desire war when fear, interest, or honor move them to fight for their community against opposing communities. War shows the best and the worst of human nature. Ware manifests the brutal cruelty of human beings in fighting those they regard as enemies. Yet war also manifests the moral sociality of human beings in fighting courageously for their group. One of the prime causes for the emergence of large, bureaucratic states is the need for increasing military power. War is an instrument of politics, and like political rule generally, warfare is a predominantly male activity.

Of all the desires on my list, this is the one that has provoked the most criticism from my readers, who don't like my claim that war is natural, and that it provides the conditions for displaying moral virtues like courage. Although Gat insists that his study of war has "no normative implications" (144), his reasoning generally supports my position.

We begin with the question of whether war is grounded in human nature, or whether it is a purely cultural invention of human history that transcends animal nature. To answer that question, we must look to what Gat calls the "human state of nature"--the original state of human beings living as hunter-gatherers, which was the state in which the genetic evolution of the human species was formed.

In their evolutionary natural way of life as hunter-gatherers, did humans fight? The enduring debate over this question has been divided between those on the side of Hobbes and those on the side of Rousseau. Hobbes answers that yes, the state of nature was a war of all against all, from which human beings escaped only by establishing a Leviathan state to keep the peace. Rousseau answers that no, the original condition of humans was peaceful. "Aboriginal humans lived sparsely and generally harmoniously in nature, peacefully exploiting her abundant resources. Only with the coming of agriculture, demographic growth, private property, division of class and state coercion, claimed Rousseau, did war, and all the other ills of civilization, spring up" (5).

Gat shows that Hobbes exaggerated the harshness and solitariness of the hunting-gathering way of life. Human beings are naturally social and political animals who began their evolutionary history living in families and in local and regional groups bound together by ties of kinship, language, and culture. But Gat also shows that Hobbes was right in seeing the propensity to warfare as part of the natural condition of humanity.

Thus, Gat resolves the Hobbes-Rousseau debate by concluding that Hobbes was closer to the truth, and he does this by surveying new knowledge drawn from the study of animal aggression, the study of surviving hunter-gatherers, the archaeological evidence for prehistoric hunter-gatherers, and evolutionary theory as providing a general explanatory perspective. Although he does not recognize it, Gat's depiction of the "evolutionary state of nature" conforms closely to the hunter-gatherer state of nature described by John Locke, David Hume, and Adam Smith. This is a good illustration of how modern evolutionary science can clarify, if not resolve, some of the enduring questions in the history of political philosophy.

In examining the issue of war among hunter-gatherers, Gat moves through through three questions. Did they fight? Why did they fight? How did they fight?

DID THEY FIGHT?
In the twentieth century, the anthropological study of war was dominated by the Rousseauean claim that warfare was a recent cultural invention in human history that was not rooted in human nature. Lawrence Keeley's War and Civilization: The Myth of the Peaceful Savage (1996) challenged this view with overwhelming evidence of warfare in pre-state societies. But Keeley's argument was weakened by the fact that he concentrated on the Neolithic period, when people adopted agriculture and animal husbandry (about 10,000 years ago), but before the establishment of states. The Rousseaueans could argue that it was the transition to agriculture that was crucial to the emergence of war, because this brought valuable stored food and other property that was worth fighting for. Consequently, the evidence of war in pre-state agricultural societies might not apply to hunter-gatherers who lived prior to 10,000 years ago.

Gat's contribution here is to extend the evidence for warfare back into hunter-gatherer history. Hunter-gatherer society consisted of local groups (20-70 members) and regional groups (an average of 500 members), bound together by language, intermarriage, rituals, exchange, alliances, and military activity. They were nomadic, and they had few possessions. Although they were remarkably egalitarian, because there was no formal and fixed status hierarchy, these societies were not totally equal, because some people who were talented and ambitious could exercise leadership, particularly in war (14, 22, 26, 32, 71-72, 74, 88-92, 138).

Gat's claim about hunter-gatherer warfare is qualified. His claim is "not that all hunter-gatherers invariably fight," because he recognizes that in all human societies throughout history, there are long periods of peace. Here is where Gat disagrees with Konrad Lorenz and others who have argued that human beings have an instinct for killing that must invariably be satisfied in some way. But Gat does claim that there has always been warfare from time to time.

The problem, however, is that the knowledge of the hunting-gathering way of life in the Pleistocene era (from two million to 10,000 years ago) is inherently inconclusive. There is some archaeological evidence for war--for example, burial remains of people apparently killed by violence and rock art depictions of war. The studies of historically recorded hunter-gatherers also shows evidence for war. But here we face the "contact paradox": since hunter-gatherers have no written records, documentary evidence depends on contact with literate people, and this contact can "contaminate" what is being observed. Consequently, the Rousseaueans can always argue that what we see of hunter-gatherers after contact is not the true story of what they looked like before contact.

To overcome this problem, Gat looks for a natural "laboratory"--a case where we can see a hunter-gatherer society that has experienced little or no change from contact with literate people. Gat sees two such "laboratory" cases. The first case is of the "simple" hunter-gatherers in Australia. The second is of "complex" hunter-gatherers in the Pacific Northwest of North America. Although much of the anthropological debate over hunter-gatherers has been dominated by the case of the African Bushmen, Gat rightly insists that it's not the best case to study because the Bushmen had been pushed into desolate environments by competition with other groups.

When Europeans began arriving in Australia in 1788, the remote areas of the interior and the north were the locales for hunter-gatherers who had no agriculture or pastoralism. There were as many as 300,000 hunter-gatherers, in 400-700 regional groups, with 500-600 people each. Their lives were simple. They didn't even have bows. Their only long-range weapon was the boomerang. Although nomadic, their movements were within a circumscribed territory, and they enforced the boundaries of their group territories.

Among these Australian aboriginals, there were violent disputes based on women, murder, and territorial trespass. Although each group enforced a rough equality, there were differences in status and influence, as in leadership by the most skillful warriors. There were trading networks extending over long distances.

The high rates of killing in war was first reported by William Buckley, who arrived in Australia in 1803 as a 13-year-old-boy from England on the first convict ship. Buckley escaped and lived with an Aboriginal tribe for 35 years. He learned their language and participated in their daily activities. Later, his reports on his experiences were recorded. And while there is some dispute over the accuracy of his stories, this seems to be the best account of a hunting-gathering society before any extensive contact with literate people. Buckley's testimony supports Gat's claim that even the simplest kind of hunting-gathering society showed warfare.

A more "complex" form of hunting-gathering society arises in rich wildlife areas, such as swamps, lakes, river mouths, and seashores. In such rich ecological niches, human population can be dense, life is more sedentary, food is accumulated, there is extensive division of labor, trade, and property, with rich individuals exercising control over resources.

The Indians of the Pacific Northwest coast of North America show this kind of society, and they show evidence of warfare and slavery through war stretching back for thousands of years.

This evidence shows that for both "simple" and "complex" hunter-gatherers, warfare was part of the "evolutionary natural way of life."

WHY DID THEY FIGHT?
I agree with Gat that--contrary to Freud, Lorenz, Tinbergen, and Storr--there is no "basic aggression instinct" comparable to the instinctive drives for food and sex. The drives for food and sex are unavoidable. But people can live in peace their entire lives without feeling any distress. Aggression is not a biological end, but a biological means to the primary biological ends.

War is "both innate and optional" (40). It is innate, because humans are naturally inclined to go to war whenever the benefits of war seem greater than the costs. Yet war is optional, because it fluctuates in response to changing conditions of life.

The evolution of war required group selection in which groups bound together by kinship relations, marriage, and cultural identity competed with one another. Religion can be understood as an evolutionary adaptation for cooperation in group selection. Gat agrees with the group-selection explanation of religion developed by David Sloan Wilson, although Gat notes that Wilson "overlooks the military aspect" of this.

Over the past thirty or forty years, there has been an intense debate among anthropologists as to the motivations for war in primitive societies. Some materialist anthropologists like Marvin Harris have stressed the importance of competition for food. Some evolutionary anthropologists like Napoleon Chagnon have stressed the importance of competition for women. According to Chagnon, when he asked Yanomamo men about this, they answered: "We like meat, but we like women a whole lot more."

Gat rightly points out that Chagnon was only partially correct about this, because he did not see how evolutionary theory allows us to see how many different factors can influence war. Evolutionary science suggests that the ultimate causes of adaptive human behavior are either somatic (concerned with the resources necessary for survival) or reproductive (concerned with mating and offspring). Thus, food and sex are primary needs or desires.

Yet there are also many secondary motivations for war that are ultimately instrumental (from the evolutionary perspective) to the somatic and reproductive motivations. These secondary motivations include dominance, revenge, fear, suspicion, supernatural elements, cannibalism, playfulness, adventurism, sadism, and ecstasy.

I see these secondary motivations as tied to various natural desires on my list of twenty--such as social status, political rule, justice as reciprocity, property, and the desire for religious understanding. I also agree with Gat that many of these motivations reflect the distinctly male propensities for risky violence and adventure.

Although the evolutionary explanation of war assumes that military violence is generally adaptive, it also recognizes that there is a lot of maladaptive and purposeless violence. So, for example, the sadism that is sometimes manifest in war can be understood as a deviation from an evolutionarily shaped norm.

HOW DID THEY FIGHT?
Human hunter-gatherers show a pattern of warfare similar to that of chimpanzees. Young adult males form raiding parties that attack only when they outnumber their opponents and thus can minimize the risk to themselves. When opposing groups face one another in open lines of battle, they prefer to engage in ritualistic bluffing displays, rather than going to battle.

There is one crucial difference between the humans and the chimps, however, in that among the human hunter-gatherers, there is a higher rate of mortality for adults. Gat identifies this as a pattern of "asymmetrical, first-strike killing." Hunter-gatherer warriors prefer to launch surprise attacks on their enemies--typically, at night when their victims are asleep and thus vulnerable.

The difference between humans and other animals is that human tool-making allows the humans to increase their offensive capability. But this also makes humans more vulnerable to attack, because as humans become more dependent on tools, their bodies become more slender and less robust than is the case for their primate ancestors. Adult male chimps carry their weapons in their bodies--powerful jaws and a physically strong build. Adult male humans lose this, and thus they become vulnerable to surprise attacks.

As a consequence, human hunter-gatherers are caught in what international relations theorists call the "security dilemma": they live in a state of fear and distrust, anticipating that they are vulnerable to surprise attacks, which inclines them to pre-emptive strikes, which only increases the state of mutual distrust. Thus, they are caught in a kind of "prisoner's dilemma" situation, where everyone is worse off than they would be if they could trust one another to cooperatively keep the peace. Hobbes saw this, and this is what led him to his dark view of the state of nature as full of fear and continual dangers.

Gat concludes this first part of his book by insisting that "the evolutionary logic in itself has no normative implications."

We may choose to follow such predispositions or rebel against them. There is nothing sacred or morally compelling about maximizing survival for the fittest. This is merely the blind, algorithmic mechanism of natural 'design.' The human brain--itself a product of evolution and a powerful instrument of conscious, purposeful, and future oriented, rather than blind, design--may come up with more satisfactory arrangements. (144)

Gat doesn't explain exactly what he has in mind here. Obviously, he is doing what evolutionary psychologists often do to avoid questions about the moral implications of their work: invoke the fact-value distinction and declare that, of course, human beings are free to appeal to moral values formulated by human reason as transcending the factual world of empirical science. But this seems to leave us with a radical dualism where the moral realm of human rational artifice floats free of the natural world. If this is so, then what is most distinctly human cannot be explained by science because it belongs to some kind of transcendental realm--perhaps Kant's realm of human freedom.

I agree that human beings do have some freedom of judgment that comes from their capacity for deliberate thought and choice. But I argue that this human freedom of judgment is constrained both by human nature and by human culture. So, in matters of war and peace, we can look for ways to promote peace and minimize war. But given our natural propensities towards war when we face severe conflicts between groups, we cannot realistically expect to achieve a world of perpetual peace.

Some posts on related topics can be found here, here, here, here., here., and here.

Pinker's List: A Distorted Record of Prehistoric War?

In his Nobel Peace Prize Acceptance Speech in 2009, President Barack Obama had to justify the awarding of the Nobel Peace Prize to a Commander in Chief who was leading his country in two major wars.  He argued that war is so deeply rooted in human nature and the human condition that it can never be completely abolished.  He declared: "War, in one form or another, appeared with the first man."  And yet, explaining how we can and should strive for peace, he quoted from President John Kennedy: "Let us focus on a more practical, more attainable peace, based not on a sudden revolution in human nature but on a gradual evolution in human institutions."  He then repeated that last phrase--"a gradual evolution of human institutions"--as the theme for his speech.  Without trying to change human nature, we can promote peace through institutional evolution--through culturally evolved norms of just war, human rights, global commerce, and international sanctions for punishing unjustified violence.  Obama thus summarized the argument of Steven Pinker that while war and violence express the "inner demons of our nature," we can move towards a life of peaceful coexistence as long as our cultural environment strengthens the "better angels of our nature."

Some of the critics of Pinker's argument think this is deeply mistaken because of its false claim that war has roots in human nature.  For example, in his book chapter--"Pinker's List: Exaggerating Prehistoric War Mortality"--R. Brian Ferguson challenges Pinker's evidence for prehistoric war that would support Obama's claim that "war, in one form or another, appeared with the first man."  (Ferguson's chapter appears in War, Peace, and Human Nature: The Convergence of Evolutionary and Cultural Views, edited by Douglas Fry [Oxford University Press, 2013].  A copy is available online.)

Ferguson concentrates his attention on Pinker's Figure 2-2 (page 49), which presents a list of societies showing the percentage of deaths in warfare in nonstate and state societies, classified into four groups: prehistoric archaeological sites, hunter-gatherers, hunter-horticulturalists and other tribal groups, and states.  The bar graphs show that the percentage of deaths in war is much higher for the first three groups than it is for states (ranging from ancient Mexico before 1500 CE to modern states from the 17th century to the present).

Ferguson claims that if one looks at the original sources for this data cited by Pinker, one discovers that Pinker's visual graph distorts the data to make it appear more supportive of his argument than it really is.  First, one should notice that among the 21 groups of prehistoric gravesites, the oldest archaeological site (Gobero, Niger, 14,000-6,200 BCE) has no war deaths at all.  And a couple of the prehistoric sites (Sarai Nahar Rai, India, 2140-850 BCE, and Nubia, 12,000-10,000 BCE) have only one violent death each.  If three skeletons are found at a site, and one of them shows evidence of violent death, then Pinker presents this as a bar graph showing 33% of deaths in war, which is much higher than that for modern states.  Surely, Ferguson suggests, one violent death at one gravesite hardly shows extensive warfare, but Pinker does not explain this to his reader.  Moreover, Ferguson notes, one set of 30 sites is from British Columbia, 3,500 BCE to 1674 CE.  Although he concedes this evidence for warfare, Ferguson indicates that these Indians along the Pacific Northwest Coast were "complex" hunter-gatherers--that is, hunter-gatherers who had settled into large villages with some hierarchical social structures, which was not characteristic of the nomadic hunter-gatherers who were our original ancestors.

Pinker presents bar graphs showing a range of 5% to 60% deaths in warfare for 8 hunter-gatherer societies.  But Ferguson points out that Pinker does not tell his reader that for two of these societies (the Ache of Paraguay and the Hiwi of Venezuela-Columbia), all of the war deaths were indigenous people killed by frontiersmen.

Pinker's bar graphs for 10 societies of hunter-horticulturalists and other tribal groups show a range of 15% to 60% deaths in warfare.  The 60% rate of death in war is the highest rate ever recorded by anthropologists, and it's for the Waorani of Eastern Ecuador.  When I was travelling through the Ecuadorian rainforest last summer, I heard about the Waorani and their reputation for violence.  One of my Quichua guides identified them as auca--"savages."

Ferguson concedes that the archaeological and anthropological evidence shows intense warfare among many complex hunter-gatherers and horticulturalists, but he argues that nomadic hunter-gatherers would not have shown this.  When one sees evidence of one or a few violent deaths among a group of nomadic hunter-gatherers, this should be identified as homicide not war.

Like Douglas Fry, Ferguson agrees that there has been lethal violence among nomadic hunter-gatherers, but this was personal violence rather than war.

In defense of Pinker, one could argue for Richard Wrangham's distinction between "simple" and "complex" war.  Like chimpanzees, nomadic hunter-gatherers do not fight pitched battles under the formal command of military leaders, because such "complex" warfare arises only in agrarian societies with military and political hierarchies.  Nomadic hunter-gatherers will kill members of outside groups only when the killers can surprise their outnumbered victims and then retreat after killing only a few individuals.  This raiding and feuding will not result in large numbers of battle deaths, and thus the archaeological record will not show any evidence of large numbers of violent deaths among nomadic hunter-gatherers.  Moreover, Pinker and Wrangham would predict that violent raiding and feuding among hunter-gatherers is infrequent, with long periods of peace, although the rate of killing is still comparable to that of American cities today.

Ferguson concludes: "We are not hard-wired for war.  We learn it" (126).

He does not indicate that those like Pinker and Wrangham actually agree with him about this.  They agree that war is not a biological necessity, although there are biological propensities to violence that can be triggered by the social environment.  They also agree with Ferguson that the establishment of agrarian societies with bureaucratic states created "complex" warfare as a purely cultural invention.  They also agree that the cultural evolution of recent centuries can move us towards peace.

Pinker and Wrangham agree with Obama and Kennedy:  in the quest for peace, we need not a sudden revolution in human nature but a gradual evolution in human institutions.

Some of these points are developed in earlier posts here, here, here., here, and here.

ADDENDUM
Brian Ferguson has pointed out to me that I have made a mistake here in attributing to him the point about the Hiwi and the Ache, because Ferguson only deals with the archaeological data in Pinker's list.  Actually, the point about the Hiwi and Ache was made by Douglas Fry (17-18).

The Evolution of War among Humans and Chimpanzees

I have written many posts about the debate between the Hobbesian and Rousseauean social scientists over the evolution of war.  In recent weeks, there have been new contributions to that debate.  On the Hobbesian side, Napoleon Chagnon and his colleagues have just published an article in the Proceedings of the National Academy of Sciences on warfare among the Yanomamo.  On the Rousseauean side, Douglas Fry has just published an article in the Journal of Aggression, Conflict, and Peace Research criticizing the myths about war among nomadic foragers.

The Yanomamo are an indigenous tribal population of foraging horticulturalists who live in the Amazon rainforest along the border region of southern Venezuela and northern Brazil.  Chagnon is one of the most famous anthropologists who has studied them.  He has provoked intense controversy with his depiction of the Yanomamo as the "fierce people" and with his claim that those men who engage successfully in lethal coalitionary warfare tend to have more wives and offspring and thus greater reproductive fitness than other men, which suggests that warfare is an evolutionary adaptation.  Moreover, Chagnon also accepts Richard Wrangham's "chimpanzee model" for explaining the evolution of warfare--the idea that the common ancestor of chimpanzees and humans engaged in the sort of male coalitionary raiding that can be observed in chimpanzees.

The social organization of lethal coalitionary aggression differs, however, between chimpanzees and humans.  Among chimpanzees, the raiding parties are genetically related males from the same natal community.  Among human foragers, the raiders are largely related by marriage rather than genetic kinship.  Rather than a "band of brothers," Chagnon and his colleagues indicate, human raiding parties are a "band of brothers-in-law."  The evolutionary advantage for men who form alliances for raiding is that this gives them access to their friends' female relatives as potential wives.

The underlying assumption here--that warfare was an evolutionary adaptation for human foraging bands--is challenged by Fry.  He argues against what he identifies as four myths:  that nomadic foragers are warlike, that there was a high rate of warfare in the Pleistocene, that the data support Wrangham's "chimpanzee model" for the evolution of war, and that the establishment of formal state bureaucracy brought an inevitable decrease in the aggression in forager societies.

In a previous post last year, I have summarized the five objections from Wrangham and his colleagues to Fry's arguments.  In this new article, Fry responds to one of those objections.  Wrangham and Glowacki have argued that in surveying the data on foraging societies, the only appropriate cases for assessing their chimpanzee model are nomadic foraging societies living next to different nomadic foraging societies, because most of the nomadic foragers studied by anthropologists have been constrained by neighboring farming societies that could dominate them politically and militarily.  If one looks at hunter-gatherer societies with neighboring societies of hunter-gatherers, Wrangham and Glowacki argue, one sees a universal pattern of warfare.

In response to this, Fry accuses Wrangham and Glowacki of cherry-picking their cases and thus relying on a biased sample of cases.  According to Fry, this ignores the many cases that work against their argument: "For instance, ethnographic cases of forager communities living in proximity to one another but that lack raiding, ambushes, feuding, or 'shoot-on-sight' practices include the nomadic foragers of central peninsular Malaysia such as the Batek, Chewong, and Jahai (Endicott and Endicott, 2008, 2014; Endicott, 2013; Howell, 1989; Sluys, 2000), the Montagnais, Naskapi, and East Main Cree bands of Labrador, Canada (Lips, 1947), and the neighboring South Indian forager societies described by Gardner (2013)" (262).

From my examination of these cases, however, I don't see how they support Fry's characterization.  For example, Lips reports that the Montagnais-Naskapi bands of the Labrador peninsula of Canada were bound together by the same language and a common culture and that they had never fought a war with one another.  But he also reports that they had fought wars against the Eskimo and the Iroquois (399).  Moreover, Lips indicates that these bands were constrained by the authority of the Canadian government and by their economic and social dependence on the Hudson's Bay Company.

Similarly, Kirk Endicott reports that the Batek of peninsular Malaysia lived under the authority of the Malaysian state of Kelantan acting through the Department of Aboriginal Affairs and the Department of Wildlife and National Parks.  He also reports: "Probably the original reason the Batek prohibited fighting with outsiders was the fear that they would be killed or enslaved.  Like other Orang Asli, they were victims of slave raiding by Malays during the nineteenth and early twentieth centuries" (2013, 248).

Sluys reports the same situation for the Jahai of northern peninsular Malaysia.  First, they were enslaved by Malays, and then they were put under strict control by the Malaysian government.

Gardner reports that the South Indian foragers have been constrained first by the British and then by the Indian government.  "In most instances, most have been isolated from one another for centuries, if not millennia, by farming peoples on the intervening plains" (Gardner 2013, 311).

So none of these cases fulfill the conditions specified by Wrangham and Glowacki.  None of these cases can serve as proxies for the nomadic foragers of the Pleistocene.

REFERENCES
Douglas P. Fry and Patrik Soderberg, "Myths About Hunter-Gatherers Redux: Nomadic Forager War and Peace," Journal of Aggression, Conflict, and Peace Research 6 (2014): 255-66.

Shane J. Macfarlan, Robert S. Walker, Mark V. Flinn, and Napoleon A. Chagnon, "Lethal Coalitionary Aggression and Long-Term Alliance Formation among Yanomamo Men," Proceedings of the National Academy of Sciences, early edition (2014).

Some of my previous posts on the debate over the evolution of war can be found here, here, here, here, here, here, here, here, and here.