Wednesday, July 24, 2013

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.


"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.


Anonymous said...

I am struck that (post)modern approaches to war--particularly the distinguishing between warriors (military) and their support system (civilians)--promote war by allowing weaker enemies to behave as hunter-gatherers, fighting only in favorable conditions. A military force should only fight when this battle is necessary to defend the community an its resources. Therefore, countries like the United States must defend the fields, while their enemies tend to only need to access the supply at times. If a aggressive military force can force the enemy to protect the providers and not have provisions (IE the Sherman and Sheridan models), then a weaker force will destroy itself protecting rail-heads or rice paddies.

I guess I'm not an anthropologist.

Anonymous said...

Well, Nature is trying to kill us humans.

Larry Grant said...

Good article.

Reading it reminded me of a recurring complaint among military historians that few universities and colleges support the study of military history, largely it seems, for the same reason you mention in the final paragraphs--that is, those with an interest in seeing the end of war suppose that studying and talking about it somehow perpetuates it.

That's an interesting notion among otherwise rational people who would consider it an archaic superstition to suppose that you could banish disease or evil (another thing they rarely believe in) by refraining from speaking of it.

George Henderson said...

"Ain't gonna study war no more."

Most sensible article.