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New Study of Prehistoric Skeletons 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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When did war begin? Does war have deep roots, or is it a modern invention? A new analysis of ancient human remains by anthropologists Jonathan Haas and Matthew Piscitelli of Chicago’s Field Museum provides strong evidence for the latter view. [*See also next post, "Survey of Earliest Human Settlements Undermines Claims That War Has Deep Evolutionary Roots."]

13,000 year old skeletons in mass grave near Nile are oldest evidence of group violence.

But before I get to the work of Haas and Piscitelli, I’d like to return briefly to my last post, which describes a study of modern-day foragers (also called hunter gatherers), whose behavior is assumed to be similar to that of our Stone Age ancestors. The study found that modern foragers have engaged in little or no warfare, defined as a lethal attack by two or more people in one group against another group. This finding contradicts the claim that war emerged hundreds of thousands or even millions of years ago.

Defenders of the Deep Roots Theory have leveled various criticisms at the forager study. [*See Clarification below.] They complain that foragers examined in the study—and modern foragers in general–have been pacified by nearby states. Or the foragers are “isolated,” living in remote regions where they rarely come into contact with other groups. In other words, these foraging societies are atypical.

But you could argue that all modern tribal societies are atypical, including those cited by Deep Rooters as evidence for their position. Take, for example, the infamous Yanomamo, an Amazonian society that is extremely warlike, according to anthropologist Napoleon Chagnon, who began observing them in the 1960s.

The Yanomamo practice horticulture, which makes them a poor proxy for nomadic Stone Age hunter gatherers. Atypical. Moreover, even Chagnon acknowledges that some Yanomamo are much violent than others. Of course, Deep Rooters assert that these relatively peaceful Yanomamo are atypical.

When Deep Rooters complain that a society is atypical, they really mean that the society is not as violent as predicted by the Deep Roots theory. They are guilty of egregious confirmation bias, and circular reasoning.

Deep Rooters display this same trait when it comes to Pan troglodytes, our closest genetic relative. Since the mid-1970s, researchers have observed chimpanzees from one troop killing members of another troop–proving, Deep Rooters claim, that the roots of intergroup violence are even older than the Homo genus.

Deep Rooters conveniently overlook the fact some Pan troglodytes communities have been observed for years without carrying out a lethal raid. Moreover, researchers have never observed a deadly attack by the chimpanzee species Pan paniscus, also known as Bonobos. Deep Rooters insist that only the most violent chimps are representative of our primordial ancestry, even though Pan paniscus is just as genetically related to us as Pan troglodytes.

To be fair, proponents of the view that war is a recent cultural invention—I’ll call them Inventors–also play this game. They find reasons to discount extremely violent behavior–by either chimps or humans—as atypical. For example, both chimp raids and Yanomamo warfare may be responses to recent encroachment on their habitat by outside societies.

But Inventors can also point to a far more persuasive source of data supporting their position: the archaeological record. The most ancient clear-cut evidence of deadly group violence is a mass grave, estimated to be 13,000 years old, found in the Jebel Sahaba region of the Sudan, near the Nile River. Of the 59 skeletons in the grave, 24 bear marks of violence, such as hack marks and embedded stone points.

Even this site is an outlier. The vast majority of archaeological evidence for warfare—which consists of skeletons marked by violence, art depicting battles, defensive fortifications, and weapons clearly designed for war rather than hunting—is less than 10,000 years old.

Deep Rooters try to dismiss these facts by resorting to the old argument that absence of evidence does not equal evidence of absence. They allege, in other words, that there is not significant evidence of any human activity prior to 10,000 years ago.

To rebut this charge, Haas and Piscitelli recently carried out an exhaustive survey of human remains more than 10,000 years old described in the scientific literature. They counted more than 2,900 skeletons from over 400 different sites. Not counting the Jebel Sahaba skeletons, Haas and Piscitelli found four separate skeletons bearing signs of violence, consistent with homicide, not warfare.

This “dearth of evidence,” Haas continued, “is in contrast with later periods when warfare clearly appears in this historical record of specific societies and is marked by skeletal markers of violence, weapons of war, defensive sites and architecture, etc.”

Haas and Piscitelli present their data in “The Prehistory of Warfare: Misled by Ethnography,” a chapter in War, Peace, and Human Nature, a collection of essays published this year by Oxford University Press. The book was edited by anthropologist Douglas Fry, co-author of the forager study I described in my last post.

“Declaring that warfare is rampant amongst almost all hunters and gatherers (as well as those cunning and aggressive chimpanzees) fits well with a common public perception of the deep historical and biological roots of warfare,” Haas and Piscitelli write. “The presumed universality of warfare in human history and ancestry may be satisfying to popular sentiment; however, such universality lacks empirical support.”

Many people think that war, if ancient and innate, must also be inevitable. President Barack Obama seemed to be expressing this notion in 2009 when he accepted the Nobel Peace Prize, just nine days after he announced a major escalation of the U.S. war in Afghanistan.

“War, in one form or another, appeared with the first man,” Obama said. He added, “We must begin by acknowledging the hard truth: we will not eradicate violent conflict in our lifetimes.”

When will Deep Rooters acknowledge that they are wrong?

Clarification: Some readers might conclude based on my criticism of Deep Rooters that they are all hawks, warmongers, who think that war, because it is innate, is inevitable and perhaps even beneficial in some sense. Such views were once quite common, especially in the era of social Darwinism. President Teddy Roosevelt once said, for example, “All the great masterful races have been fighting races. No triumph of peace is quite so great as the supreme triumph of war.” None of the Deep Rooters I have cited subscribe to such odious balderdash. All fervently hope that humanity can eradicate or at least greatly reduce the frequency of war. Deep Rooters believe that we will be better equipped to solve the problem of war if we accept the Deep Roots theory. Of course, I disagree with them on this point. As indicated by the above comments of President Barack Obama—as well as comments on my blog–the Deep Roots Theory leads many people to be pessimistic about the prospects for ending war, a view that can be self-fulfilling. I would nonetheless accept the Deep Roots theory if the evidence supported it, but the evidence points in the other direction. That is my main source of disagreement with Deep Rooters. In the interests of constructive dialogue, however, I’m providing a link, sent to me by anthropologist and prominent Deep Rooter Richard Wrangham, to a column supporting his position. In the column, political scientist and self-described “conservative Darwinian” Larry Arnhart asserts that “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.” Okay, so we all want peace. We just disagree on how to get there. More to come.

Photo of Jebel Sahaba grave by Fred Wendorf, http://www.chaz.org.

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 4:24 pm 07/24/2013

    Well at this point in human history it doesn’t much matter to me whether war “appeared with the first man” or is a relatively modern invention. The civilizations that developed in the past 10,000 years can be considered ancient even if anthropologists want to count them as modern. Ancient Greece, ancient Rome, ancient Egypt, ancient Persia, ancient China, Sumerians, Babylonians, Assyrians, Hittites, all pretty ancient stuff and chock full of warfare. Most people would consider that ancient history, probably even Obama. He does not strike me as someone who spends a lot of time investigating human history and anthropology prior to 10,000 years ago. Anthropologists I think would agree that our understanding of human societies 10,000 years ago is pretty sparse. Maybe warfare between different societies did begin 13,000 years ago in the Sudan. Maybe it began earlier. Maybe there was a time before war but that doesn’t change what we have become. Three hundred to four hundred generations is a long time, a lot of history, a lot of learning the practice of war. It has become the accepted way to deal with unacceptable and seemingly insoluble situations – Palestine. It has become the accepted way to promote ideology – Islam, communism, and even democracy. It has a very long (although not anthropologically ancient) history in the post ice age story of mankind.

    If someone wants to claim we can’t do anything about war that is just false. We can. If someone wants to claim that it would be easy because it is a modern, 10,000 years or so, invention that is also false. It will not be easy. We, the people of the world, have a long way to go before we can engage the better angles of our nature but Steven Pinker thinks it has already begun. I’m not sure I agree with him, his work is very controversial, but his views should be part of the conversation on how we might end war and the oppression of others.

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  2. 2. Traveler 007 4:43 pm 07/24/2013

    Also some proof that #2 pencils have been around since the stone age

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  3. 3. RogerPink 4:44 pm 07/24/2013

    It’s pretty obvious that war is an evolved trait given the behavior of Chimpanzees combined with all of the instances of war throughout history. The suggestion that it’s otherwise smacks of an agenda. Reports like these remind me of the studies cited by Global Warming skeptics.

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  4. 4. Owl905 6:01 pm 07/24/2013

    The article doesn’t really make a case for warfare and civilization being dance partners. The Sumerians back to the semi-mythical age of Gilgamesh were promoting warfare since creation – it was considered a trait of the Gods. Religious text and myths marks early tribal memories with the trauma of warfare.
    The lack of warfare implements means nothing. The attacks of group-on-group has evidence in the artifact of cannibalism. Modern day foragers aren’t anachronisms of ancient hunter-gatherers – they’re anomalies of a modern civilized world.
    The survey of skeletons is compelling evidence, but it is distorted by the exclusion of definitive evidence of a per-civilization battle 13,000 years ago..
    Combined with the resort to hyperbole about “rampant” warfare, the study still lands face down as a romantic re-statement of the noble savage Paradise messed up by human civilization.

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  5. 5. ultimobo 6:26 pm 07/24/2013

    interesting observation that war may have been less likely amongst hunter-gatherers – I wonder if the increase in war may be associated with horticulture, in other words something to defend.

    When everyone gets their food by going into the forest and looking for it, I’d guess folk have no energy left for fighting each other.

    When people grow their food at home, with a stable water supply, that could suggest an easy food source if you just come in and take over, requiring the farmers/animal rearers to want to defend their investment – and thus the rise of warfare ?

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  6. 6. GWIA? 9:12 pm 07/24/2013

    One of the reason “deep rooters” site examples of modern day hunter gatherers as atypical is that they tend to live in atypical environments, environments not suited to agriculture or livestock raising, like those of the deserts of the Kalahari.

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  7. 7. way2ec 1:11 am 07/25/2013

    I like the way the author has opened up the “debate” about the roots of warfare with some data, the survey of ancient skeletons. We should continue to speculate about the origins of war, don’t know where you’re going until you know where you’ve been. As to a “hidden agenda” and or “noble savages”, bah humbug. Whatever your point of view, show some evidence. Did Cro-Magnon Man hasten the demise of the Neanderthals? That debate takes us back to 35,000 years ago. No evidence (that I know of) in the cave art of warfare (or murder for that matter). Yes, defending your territory, or the taking of someone else’s might very well be the origin of war and before that time, population numbers alone would argue against warfare. People’s need for “outbreeding” would favor neighborliness over warfare (as evidenced in our having Neanderthal genes?) Does “Make love not war” suggest “noble savages” in a primitive pristine world, even as it might have spelled doom for the Neanderthals? Or will the “Deep Rooters” suggest rape and pillage has gone hand in hand with warfare? And since we are on the topic, what are the evolutionary genetics of genocide, and does anyone care to date its origin? Since nuclear holocaust is such a modern invention, does that imply we are anything but “noble savages”, never have been never will be?

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  8. 8. Owl905 3:09 am 07/25/2013

    Way2 substitutes hosts of questions for content, but the gem in the comment is the pointer to paleolithic and neolithic rock art. And that lands with a thump clearly, and decisively, supporting savage warriors predating ‘civilization’. A search on “Rock Art Warfare” opens the door to ubiquitous depictions of combat between ancient groups.
    At the other end of the balance is the dearth of battle-injured remains. The rock art depicts post-battle executions. South American pre-Columbian civilizations had a gold standard of sacrificial execution of prisoners. Maybe the review of 2900 ad hoc remains isn’t a representative sample.

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  9. 9. David Cummings 6:45 am 07/25/2013

    I agree that evidence is the only way to solve this question, rather than personal preferences. I try to have no preference on subjects like these. I just enjoy reading further developments in the uncovering of evidence.

    Taking Owl’s suggestion, I clicked on the first link of the search he recommends and found an interesting paper:

    http://www.academia.edu/1078438/Warfare_in_Spanish_Levantine_rock_art

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  10. 10. David Cummings 6:47 am 07/25/2013

    I just read in wikipedia that the rock art in the link I posted above is probably between 3500BC and 8000BC, so it doesn’t add any evidence to the question of warfare 10,000+ years ago. But it still looks like an interesting paper. I’m going to read it.

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  11. 11. jgrosay 4:05 pm 07/25/2013

    Not only war is not just a recent activity, but even the classical Greeks, that some put in the top of the western civilization and in the roots of the western culture, at least we share a common ancestor for their language and ours, are highly suspicious of having practised canibalism, as their anatomical descriptions of the hip anatomy point that they’ve opened corpses when medicine was not developed enough as to practice teaching or research autopsies. Reasons for ancient wars, whenever it started? Probably just hunger, Germanic peoples that have a tradition of fighting with their neighbors and others, use for dying the word ‘sterben’, equal to the english word ‘starve’, meaning also to die, but specifically by hunger, German and English share a not too distant common language antecessor. In some languages, words for certain activities reflect part of its cultural history: in Japanese, the word for war equals ‘attack’ and the German word for war: ‘kriegen’, means ‘seizing’, ‘takeover’. Connecting apparently unconnected fields of knowledge may give you surprises.

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  12. 12. Johnceeking 9:07 pm 07/29/2013

    Have you considered the possibility that warfare results primary from unavoidable conflict over fixed resources brought about by agriculture and therefore sedentary and expanding populations? Perhaps, under the correct pressures, our primate ancestors would have responded in the same way.

    That would certainly explain the fossil record showing few signs of warfare before the onset of the agricultural revolution but considerable amounts afterward.

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  13. 13. stu44 10:24 am 07/31/2013

    The article fails to give credit to war as a means of confronting an injustice. Yes, war can be horrible, but sometimes the alternative is worse. For example: The U.S. Revolutionary War confronted British tyranny. The French Revolution confronted tyranny. The U.S. Civil War confronted the breakup of the Country. World War I and II both confronted tyranny. War is the last resort to fight injustice.

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  14. 14. WizeHowl 4:29 am 08/7/2013

    It has been shown that in some poorer countries war has broken out over the years over resources, so it is just as likely that our ancestor’s did the same when they first started horticulture. But that does not mean they didn’t fight against each other prior to then for the same reason, Resources. For as long as we have had tribal mentality I think mankind would have had some reason to protect their loved ones and their possessions from others who would want to appropriate them.

    As for Hogan, he needs to learn to edit his blogs, as usual his language is all over the place and is misleading -

    “Take, for example, the infamous Yanomamo, an Amazonian society that is extremely warlike, according to anthropologist Napoleon Chagnon, who began observing them in the 1960s.

    The Yanomamo practice horticulture, which makes them a poor proxy for nomadic Stone Age hunter gatherers. Atypical. Moreover, even Chagnon acknowledges that some Yanomamo are much violent than others. Of course, Deep Rooters assert that these relatively peaceful Yanomamo are atypical.”

    So is this tribe “extremely warlike” as described in that first paragraph or “relatively peaceful” as in the second? With just some of them been “much violent than others”?

    There was a call for him to be sacked some time ago for what he wrote in blog that was somewhat disgusting, maybe Sci-Am should sack him because he can not write proper English, or at least take the time to edit his blog before he posts it.

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