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New Study of Foragers Undermines Claim That War Has Deep Evolutionary Roots*

The views expressed are those of the author and are not necessarily those of Scientific American.


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One of the most insidious modern memes holds that war is innate, an adaptation bred into our ancestors by natural selection. This hypothesis—let’s call it the “Deep Roots Theory of War”–has been promoted by such intellectual heavyweights as Steven Pinker, Edward Wilson, Jared Diamond, Richard Wrangham, Francis Fukuyama and David Brooks. *[After reading this post, please see followup posts: "New Study of Prehistoric Skeletons Undermines Claim that War Has Deep Evolutionary Roots," "Survey of Earliest Human Settlements Undermines Claims That War Has Deep Evolutionary Roots."]

"Killer ape" scene in Stanley Kubrick's 1968 film 2001: A Space Odyssey has no basis in fact.

The Deep Roots Theory addresses not just violent human aggression in general but a particular manifestation of it, involving attacks by one group against another. Deep Rooters often contend that–as warlike as we are today–we were much more warlike before the advent of civilization.

Pinker claims in his bestseller Better Angels of Our Nature that “chronic raiding and feuding characterize life in a state of nature.” In The Social Conquest of the Earth, Wilson calls warfare “humanity’s hereditary curse.” The Deep Roots Theory has become extraordinarily popular, especially considering that the evidence for it is extraordinarily flimsy (see “Further Reading” below).

A study published today in Science, ”Lethal Aggression in Mobile Forager Bands and Implications for the Origins of War,” provides more counter-evidence to the Deep Roots Theory. The study’s authors, anthropologists Douglas Fry and Patrik Soderberg of Abo Akademi University in Finland, say their findings “contradict recent assertions that [mobile foragers] regularly engage in coalitionary war against other groups.”

Fry and Soderberg focus on mobile forager bands, also called nomadic hunter-gatherers, because their behavior is thought to provide a window into human evolution. Our ancestors lived as wandering foragers from the emergence of the Homo genus some 2 million years ago until about 10,000 years ago, when humans began raising crops, domesticating animals and settling down into more complex, hierarchical societies.

Fry and Soderberg examine data on deadly violence within 21 mobile foraging societies observed by ethnographers. The societies include the Aranda and Tiwi of Australia; Kaska, Copper Inuit and Montagnais of North America; Botocudo of South America; !Kung, Hadza and Mbuti of Africa; and Vedda and Andamanese of South Asia.

Fry and Soderberg count a total of 148 “lethal aggression events” in the societies. The researchers distinguish between violence involving people who belong to the same group and are often related; and violence between people in different groups. They also distinguish between violence involving just one perpetrator and victim and violence involving at least two killers and two victims.

These distinctions are crucial, because war by definition is a group activity. Deep Rooters often count all forms of deadly violence, not just group violence, as evidence of their theory. (They also often count violence in societies that practice horticulture, such as the Amazonian Yanomamo, even though horticulture is a relatively recent human invention.)

Of the 21 societies examined by Fry and Soderberg, three had no observed killings of any kind, and 10 had no killings carried out by more than one perpetrator. In only six societies did ethnographers record killings that involved two or more perpetrators and two or more victims. However, a single society, the Tiwi of Australia, accounted for almost all of these group killings.

Some other points of interest: 96 percent of the killers were male. No surprise there. But some readers may be surprised that only two out of 148 killings stemmed from a fight over “resources,” such as a hunting ground, water hole or fruit tree. Nine episodes of lethal aggression involved husbands killing wives; three involved “execution” of an individual in a group by other members of the group; seven involved execution of “outsiders,” such as colonizers or missionaries.

Most of the killings stemmed from what Fry and Soderberg categorize as “miscellaneous personal disputes,” involving jealousy, theft, insults and so on. The most common specific cause of deadly violence—involving either single or multiple perpetrators–was revenge for a previous attack.

These data corroborate a theory of warfare advanced by Margaret Mead in 1940. Noting that some simple foraging societies, such as Australian aborigines, can be warlike, Mead rejected the idea that war was a consequence of civilization. But she also dismissed the notion that war is innate–a “biological necessity,” as she put it–simply by pointing out (as Fry and Soderberg do) that some societies do not engage in intergroup violence.

Mead (again like Fry and Soderberg) found no evidence for what could be called the Malthusian theory of war, which holds that war is the inevitable consequence of competition for resources.

Instead, Mead proposed that war is a cultural “invention”—in modern lingo, a meme, that can arise in any society, from the simplest to the most complex. Once it arises, war often becomes self-perpetuating, with attacks by one group provoking reprisals and pre-emptive attacks by others.

The war meme also transforms societies, militarizes them, in ways that make war more likely. The Tiwi seem to be a society that has embraced war as a way of life. So is the United States of America.

The Deep Roots Theory is insidious because it leads many people to succumb to the fatalistic notion that war is inevitable. Wrong. War is neither innate nor inevitable.

Further Reading:

Horgan, “Quitting the hominid fight club: The evidence is flimsy for innate chimpanzee–let alone human–warfare“: http://blogs.scientificamerican.com/cross-check/2010/06/29/quitting-the-hominid-fight-club-the-evidence-is-flimsy-for-innate-chimpanzee-let-alone-human-warfare/

Horgan, “Will War Ever End?” (review of Better Angels of Our Nature, by Steven Pinker): http://www.slate.com/articles/Arts/books/2011/10/steven_pinker_s_the_better_angels_of_our_nature_why_should_you_b.2.html

Horgan, “No, War Is Not Inevitable” (review of The Social Conquest of Nature, by Edward Wilson): http://discovermagazine.com/2012/jun/02-no-war-is-not-inevitable#.UefeMRZ8LlI

Horgan, “Worst Column Ever By Times Pundit David Brooks: ‘When the Good Do Bad’”: http://blogs.scientificamerican.com/cross-check/2012/05/21/worst-column-ever-by-times-pundit-david-brooks-when-the-good-do-bad/

Horgan: “Are We Doomed to Wage Wars Over Water?”: http://blogs.scientificamerican.com/cross-check/2012/03/26/are-we-doomed-to-wage-wars-over-water/

Horgan, “Margaret Mead’s War Theory Kicks Butt of Neo-Darwinian and Malthusian Models”: http://blogs.scientificamerican.com/cross-check/2010/11/08/margaret-meads-war-theory-kicks-butt-of-neo-darwinian-and-malthusian-models/

Horgan, “Is ‘Sociobiologist’ Napoleon Chagnon Really a Disciple of Margaret Mead?”: http://blogs.scientificamerican.com/cross-check/2013/02/25/is-sociobiologist-napoleon-chagon-really-a-disciple-of-margaret-mead/

Horgan, “RIP Military Historian John Keegan, Who Saw War As Product of Culture Rather than Biology”: http://blogs.scientificamerican.com/cross-check/2012/08/04/rip-military-historian-john-keegan-who-saw-war-as-product-of-culture-rather-than-biology/

Horgan, “New Study of Prehistoric Skeletons Undermines Claim that War Has Deep Evolutionary Roots“: http://blogs.scientificamerican.com/cross-check/2013/07/24/new-study-of-prehistoric-skeletons-undermines-claim-that-war-has-deep-evolutionary-roots/

Horgan, The End of War, McSweeney’s, 2012.

Douglas Fry, Beyond War, Oxford University Press, 2007.

Image from 2001: A Space Odyssey courtesy Wikimedia Commons.

John Horgan About the Author: Every week, hockey-playing science writer John Horgan takes a puckish, provocative look at breaking science. A teacher at Stevens Institute of Technology, Horgan is the author of four books, including The End of Science (Addison Wesley, 1996) and The End of War (McSweeney's, 2012). Follow on Twitter @Horganism.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. M Tucker 3:51 pm 07/18/2013

    “Instead, Mead proposed that war is a cultural “invention”—in modern lingo, a meme, that can arise in any society, from the simplest to the most complex. Once it arises, war often becomes self-perpetuating, with attacks by one group provoking reprisals and pre-emptive attacks by others.”

    That may be so. I am prepared to accept that it is a cultural invention but that invention seems to be evident in the most ancient cities anthropologists have unearthed. These cities date back to that time “about 10,000 years ago, when humans began raising crops, domesticating animals and settling down into more complex, hierarchical societies.”

    War may not be “a biological necessity” or even “a consequence of civilization” but it seems to have been with us from the beginning of civilization. So, my conclusion is that it is a tremendously insidious and addictive behavior that is probably not the consequence of heredity or civilization or the competition for resources. Once learned it does seem to be self-perpetuating and justified by those who adopt it. It is not clear how fear of the ‘other’ factors into war behavior but I cannot think of how it might be possible to end war as long as bigotry, prejudice, intolerance, jealousy, lust, envy, greed, rage, and above all fear persist in our society.

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  2. 2. limbic 4:38 pm 07/18/2013

    whether the behavior of warfare is transmitted culturally or genetically (or both) does not really matter to the question whether it has been maintained by natural selection because it has some evolutionary advantage. For another option, namely that war is a consequence of the ecology of a species, see the article “lethal raiding by male spider monkeys” by Aureli et al. although spider monkeys are genetically quite distant cousins of chimps and humans, they too exhibit purposeful killing of individuals from neighboring groups just as humans and chimps. what we do share with them is a fission fusion society as a consequence of patchy food distribution.

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  3. 3. bwiley1 6:53 pm 07/18/2013

    Any chance the mobile foraging societies survive until present day to be studied precisely because they are less warlike? I.e., because they have a less warlike culture they didn’t engage the progenitors of modern society in warlike behavior and, as result, they are still around for us to study them versus having been defeated in war or otherwise integrated into modern society?

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  4. 4. rkipling 12:04 am 07/19/2013

    More of the usual gibberish undeserving of a response.

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  5. 5. aldomat 2:42 am 07/19/2013

    May I note in passing some unwarranted assumptions?

    First: “meme”. There is no such thing. It is Dawkins’ false analogy from particulate inheritance (DNA) to cultural constructs which, as linguistics shows, are very ambiguous, plastic, and continuously shaped by experience, hence not particulate at all, and therefore not inheritable. True, fragments move on in society, but that’s what they are.

    Second: “selfish”. Again a false analogy from pigeon breeding for ONE trait (DARWIN) to the idea that in the wild selection is for one (functional) trait only. Selection is for phenotype, where 20-30’000 genes coexist, and we know little of the many forces that contribute to the outcome.

    Finally: that raids happened is undisputed. Whether they were defining, contributing, or whatever is anyone’s guess. We should stop using (a false analogy once more) mechanical concepts of inevitability when looking at biological systems, which only accepts possibilities.

    KITCHER (Ethical project) and BOEHM (Moral origins) are probably closer to the truth when arguing that humanity is self-domesticating. But that does not mean that humanity was “violent” in any predispositional sense. Domestication is an emergent property of a complexifying social system.

    Finally, I’d recommend SAHLINS (The Western illusion of human nature) to see how perfidiously our Western view of “fallen humanity” and antithesis nature-culture flavor our thinking.

    Thanks to the author for helping clarify matters on violence. He is right, but we need to go deeper and see the errors of our worldview.

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  6. 6. bpappin 9:10 am 07/19/2013

    The authors of this study I think are ignoring a few important points:
    1) we have mostly not been foragers for many thousand years. We became farmers. Farmers are rooted and grow to larger populations which allows for different social dynamics where war is more likely to form.
    2) humans, even in those foraging societies that still exist, are easily capable of theft and anger. Combine that with a much larger population and you have the beginnings of war.
    3) War need not be natural for humans simply as war. But the ingredients that make us warlike *are* natural to us and only need to be combined in the right quantities for us to engage in war.
    4) They have drawn conclusions from a dataset that they purposely narrowed and where the people have long ago been adjusted by climate or geological isolation to be what they are today. If the studied populations were a good representation, then they would have been disrupted long ago by other factors.

    In my opinion, its important that we not blind ourselves to the possibilities, because although war may or may not go away all together, we can still reduce the need for it.

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  7. 7. bpappin 9:16 am 07/19/2013

    @bwhily1 exactly. The studied populations are still around to be studied because they have mostly been isolated by climate or geology. They had nobody to war with, no reason to fight, and populations too small to war with.
    However all of the social and emotional makings for war are still there, as they are in any extended family group including my own.

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  8. 8. Bryant 9:23 am 07/19/2013

    I can accept that there are no evolutionary roots to war. However, what plagues me is if war is ever ethical in the event of resource shortages which could be a factor? Should every last man be crammed into a tent on a cold winter night at the risk of killing everyone else? Everyone else can argue over whether war is innate or not, but that is the problem that bothers me.

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  9. 9. JPGumby 10:34 am 07/19/2013

    Insidious, eh? Not very scientific. Hard to imagine the experiment that falsifies something being insidious.

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  10. 10. SteveinOG 11:29 am 07/19/2013

    Conflicts instigated by individuals are almost always at the root of “war.” The vanity, greed or megalomania of leaders is the most common cause of wars large and small. If you look at any war in history you will find one ruler, group of generals, priestly cult, or ohligarchy that is the aggressor. The general population of any society just wants to get along. War is the flaw of leaders, not humanity in general.

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  11. 11. Hella 11:37 am 07/19/2013

    Really?

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  12. 12. Ryszard Byrka 4:30 pm 07/19/2013

    That was the slavery what involved the need for wars. Earlier, with a higher womens position, we had been living more peacefully, quite as Bonobo chimps do, I think.

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  13. 13. jabailo 9:34 pm 07/19/2013

    Seems like they are mixing two topics…war and genocide. For example, we have been in a large war since 911, but the casualty rate compared to our population is very low. And in the past the genocide and cost of war (starvation, winters without shelter) killed more than the actual war.

    So War might be somewhat ritualized and symbolic. I’ve heard that warring tribes often fight with weapons up until a very few are killed or just wounded. Like stags looking at each others antlers, sometimes people are just sizing each other up.

    But that doesn’t detract from genocide, or I guess a “war” in which one side has such overwhelming control that it decides a first strike annihilation is doable and so goes ahead with it.

    The existence of genocide still seems to validate the aggressive predator theories of early hominids.

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  14. 14. QuietQuest 7:34 am 07/20/2013

    Don’t forget that this is a political blog. John loses few opportunities to advance his POVs. For example, he has authored a book titled “The End of War”, so it should come as no surprise that he highlights and emphasizes opinions which corroborate his. He would, wouldn’t he?

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  15. 15. simplulo 9:55 am 07/20/2013

    I was similarly taken aback by the strange and repeated use of “insidious”, but the author’s enduring interest here is now clear. Fortunately, this study appeared in the less politically inclined Wired, so I was able to read about it without the spin. This is all quite interesting, and the jury is still out. I look forward to more studies, especially non-war explanations of men’s weird obsession with team sports. But I would find it quite strange if war turned to lack deep roots: humans are tribal, and men are clearly designed for violence (witness male-female dimorphism among polygynous primates)–it requires little innovation to put the two together and make war, with the evolutionary stakes being winner take all.

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  16. 16. Amy Luna 4:27 pm 07/20/2013

    Any research on a Peace meme?

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  17. 17. Wim Borsboom 4:50 pm 07/20/2013

    I have written a short story recounting the ecological, cultural and agricultural transitions taking place at the end of the glacial period some 12.000 years ago. I set the story in the once fertile Baluchistan hills and valleys just to the West of the Sindh Delta (the current Indus Valley in Pakistan and India) at the time of the shrinking possibilities of hunting, foraging and gathering that was brought about by the end-of-ice-age droughts causing the natural abundance of food to diminish for the – at that time – natural balanced sizes of tribes populating the now less habitable and fertile hills and valleys.
    In the story I describe the discussions between one particular tribal chief and the tribe’s ‘wise man’ on how to deal with the shortages of water and food…
    I caught them at the moment when the ‘wise man’ described his discovery of the principles of collecting seeds and nuts for the use of controlled planting in the now wetter delta regions (the end of the ice-age’s increasing glacial melting) at the bottom of the Baluchistan foothills: fruit & nut trees and purposed seeding for what later would become grain. Domestication of wild goat and swine was also one of the wise man’s ideas.
    The tribal chief though came up with a shortcut: his invention was the novel idea of raiding neighbouring tribes for their food and territory while at the same time reducing the population size of their competition: waging tribal warfare (and the concomitant repurposing of the club, lance and bow & arrow)… the early beginnings of genocide?
    Needless to say, both plans were executed, eventually resulting in what became and still is agriculture, husbandry and… territorial war mongering & genocide!

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  18. 18. David Marjanović 9:16 am 07/21/2013

    The most common specific cause of deadly violence—involving either single or multiple perpetrators–was revenge for a previous attack.

    Very unsurprising, but good to have confirmed!

    First: “meme”. There is no such thing. It is Dawkins’ false analogy from particulate inheritance (DNA) to cultural constructs which, as linguistics shows, are very ambiguous, plastic, and continuously shaped by experience, hence not particulate at all, and therefore not inheritable. True, fragments move on in society, but that’s what they are.

    …That’s exactly what Dawkins means. ~:-|

    Second: “selfish”. Again a false analogy from pigeon breeding for ONE trait (DARWIN) to the idea that in the wild selection is for one (functional) trait only. Selection is for phenotype, where 20-30’000 genes coexist, and we know little of the many forces that contribute to the outcome.

    I can’t see what this has to do with the book title “The Selfish Gene”. The point of that was simply that selection doesn’t act “to preserve the species” or something – genes are what is inherited, what mutates and spreads, what produces a phenotype (on which selection then acts) in accidental cooperation or accidental competition with other genes (in the same cell or in different organisms).

    The authors of this study I think are ignoring a few important points:
    1) we have mostly not been foragers for many thousand years. We became farmers. Farmers are rooted and grow to larger populations which allows for different social dynamics where war is more likely to form.

    The very question the study tried to answer is what humans are like without the – quite recent – influence of agriculture.

    2) humans, even in those foraging societies that still exist, are easily capable of theft and anger. Combine that with a much larger population and you have the beginnings of war.

    Well, do you have the beginnings of war, or do you instead have the beginnings of a heap of bar brawls? Or both?

    That was the slavery what involved the need for wars.

    Slavery simply isn’t old enough for this. Was there ever slavery in Australia before European colonization?

    and men are clearly designed for violence (witness male-female dimorphism among polygynous primates)

    Is it violence, or is it intimidation? Look at gorillas.

    I set the story in the once fertile Baluchistan hills and valleys just to the West of the Sindh Delta

    That’s not one of the places where agriculture was invented; and it was invented in a much more convoluted, gradual process than you imagine.

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  19. 19. AJGrayTay 3:25 pm 07/21/2013

    Of course, ‘no evidence for’ is not the same as ‘evidence suggesting there is no link’. I’m still of the opinion that Malthus was onto something – species fight for access to resources, why should we be any different? It’s all just competition. Either way, it also seems perfectly reasonable that war isn’t inevitable. Life seems flexible enough to occupy just about any niche – no reason why we couldn’t occupy a ‘warless niche’.

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  20. 20. hgintis 4:58 pm 07/22/2013

    This paper and the surrounding commentary miss the point. Of course there are many more intra-group hostilities than inter-group hostilities. So what? The major points are (a) only humans among the vertebrates wage war as a collective phenomena (many species of ants do as well), and (b) the cooperative and altruistic behaviors attributed to humans may well have come from the capacity to win inter-group wars. This was Darwin’s hypothesis and we develop it with much evidence in my book with Samuel Bowles, A Cooperative Species (Princeton, 2011).
    Of course war is an innate human predisposition. That does not mean that war is inevitable, or that war is good, or any of that claptrap. We have a predisposition to have rotten teeth. Are rotten teeth inevitable? Are rotten teeth good?
    I am afraid we are losing the war on stupid, and John Horgan is on the winning side. ;) [just kidding, John]

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  21. 21. Dr. Strangelove 2:21 am 07/23/2013

    War has evolutionary roots because chimpanzees also engage in gang war. These ape wars are motivated by territorial disputes. When other apes enter the territory of a group of apes, the outsiders get attacked and sometimes killed by the group defending the territory. Sounds familiar? If chimps have assault rifles, they’d be shooting each other. Hopefully our superior intelligence will enable us to minimize war. On the other hand, the same intelligence enables us to make weapons of mass destruction and be more effective in killing.

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  22. 22. gesimsek 5:38 pm 07/23/2013

    In most spiritual systems, there is a war inside oneself and a war outside. A person has to wage a far against his own selfish desires in order to be fully human. Those who fail on this struggle project their own shortcomings upon others by forcing them to satisfy their unfulfilled desires.

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  23. 23. MarkAA 8:22 pm 07/25/2013

    Always nice to know that journalists know better than the rest of us. It’s one thing to say that there is a study suggesting -such&such- another to suggest that such a study is definite, and the large body of work to the contrary is wrong. As some of the commenters have already noted, study is limited, and kind of beside the point – looking at current isolated groups doesn’t really go to the core question – for example, such groups may have ‘evolved’ away from what is for the rest of us a core characteristic (the sample is not representative … ) Thought provoking, but apparently designed to just be provoking.

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  24. 24. MarkAA 8:30 pm 07/25/2013

    http://www.sciencemag.org/content/341/6143/270:

    “Are hunter-gatherer societies warlike? That question has sparked a war of its own among scientists, because if war is a common feature of the foraging way of life, then perhaps it was a driving force in human evolution. A study on page 270 in Science of existing ethnographies concludes that most killings among mobile foragers today are more like murder than war. But critics challenge the study’s methods, and suggest that some of these traditional societies do indeed wage war.” Science 19 July 2013: Vol. 341 no. 6143 p. 224 DOI: 10.1126/science.341.6143.224

    So the factual premise of this article may be wrong … wrong … wrong

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