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Hames, Raymond B., "Pacifying Hunter-Gatherers" (2019). Anthropology Faculty Publications. 162.
Published in Human Nature 30 (2019), pp 155–175.
Copyright © 2019 Springer Science+Business Media, LLC, part of Springer Nature.
Used by permission.
Published 5 April 2019.
Department of Anthropology
University of Nebraska–Lincoln, Lincoln, NE, USA
There is a well-entrenched schism on the frequency (how often), intensity (deaths
ers compared with large-scale societies. To simplify, Rousseauians argue that war-
fare among prehistoric and contemporary hunter-gatherers was nearly absent and,
if present, was a late cultural invention. In contrast, so-called Hobbesians argue
that violence was relatively common but variable among hunter-gatherers. To de-
fend their views, Rousseauians resort to a variety of tactics to diminish the appar-
ent frequency and intensity of hunter-gatherer warfare. These tactics include re-
the intensity of warfare among hunter-gatherers. These tactics are subject to crit-
ical analysis and are mostly found to be wanting. Furthermore, Hobbesians with
empirical data have already established that the frequency and intensity of hunter-
gatherer warfare is greater compared with large-scale societies even though hor-
ticultural societies engage in warfare more intensively than hunter-gatherers. In
the end I argue that although war is a primitive trait we may share with chimpan-
zees and/or our last common ancestor, the ability of hunter-gatherer bands to live
peaceably with their neighbors, even though war may occur, is a derived trait that
fundamentally distinguishes us socially and politically from chimpanzee societies.
It is a point often lost in these debates.
Keywords: Hunter-gatherers, War, Chimpanzees, Peace, Comparative research
Published in Human Nature 30 (2019), pp 155–175.
Copyright © 2019 Springer Science+Business Media, LLC, part of Springer Nature.
Used by permission.
Published 5 April 2019.
30 (2019) 2
n 1997 Lawrence Keeley coined the phrase “pacifying the past” as
a critique of scholars who took what one might call a Rousseauian
the state. Along with such notions as living in harmony with the envi-
ronment (Hames 2007) and primordial sexual equality and promiscu-
ity (Ryan and Jetha 2012), Rousseauians believed that war and lethal
violence were rare or absent in small-scale societies and did not be-
come widespread and intense until settled agricultural life when war
opment of the state. Keeley’s direct experience with this perspective
stemmed from his research grants being rejected by funding agencies
because he sought to investigate what he hypothesized to be defen-
fare in non-state societies. Although his War before Civilization (Keeley
sition have responded, and a major target has revolved around the in-
tensity and frequency of warfare and lethal violence among mobile
hunter-gatherers. The terms “Hobbesians” and “Rousseauians” have
gained some currency (Gat 2015), although alternative contrasts such
as Hawks and Doves (Otterbein 2004) or warfare having a “long chro-
nology” or “short chronology” (Allen and Jones 2014) make similar
distinctions (see Allen 2014a for a review of these positions). However,
I will use the Hobbesian/Rousseauian distinction following the pene-
trating analysis by Gat (2015) wherein he uses the Australian hunter-
gatherer material to clearly expose conceptual and empirical problems
for those who would pacify hunter-gatherers. Oddly, Douglas Fry, one
of the Rousseauian leaders of this conservative counter, claims that the
“pervasive intergroup hostility model” is somehow the main orienta-
tion held by many researchers (2006:10) who investigate hunter-gath-
erer warfare. Although this allegedly pervasive model includes such
things as hunter-gatherer patrilocality and the closed nature of res-
idential bands, the key claim he seeks to refute is that warfare has a
deep history and was common among mobile hunter-gatherers. How
though comparative researchers have created measures of both war-
fare frequency, or how often it occurs (e.g., Ember and Ember 1992a),
and warfare intensity, or the probability of an individual being killed
by another human through war or homicide (Wrangham et al. 2006).
30 (2019) 3
This Rousseauian perspective runs parallel to scholars who cast
doubt on the causes, adaptive nature, and intensity of chimpanzee co-
alitionary violence. A number of researchers, most prominently Power
(2005), claim chimpanzee violence is not “natural” or adaptive and
is largely the consequence of outside factors such as research team
presence and disruptions (e.g., feeding stations) or disturbances by
farmers or the bush meat trade (Sussman and Marshack 2010). Such
claims have been empirically discounted through a comparative anal-
tact (Wilson et al. 2014). Similarly, as applied to hunter-gatherers,
tribal zone theory (Ferguson and Whitehead 1991) makes a parallel
sequence of colonial invasions.
The goal of this paper is to assess and critique a variety of positions
put forward by Rousseauians to diminish the frequency and intensity
of warfare among hunter-gatherers. These tactics include the follow-
ing: misrepresenting evolutionary theory, reclassifying hunter-gather-
gatherer violence; overemphasizing the role of colonial activities in
increasing warfare; and questionable use of archaeological evidence
and time lines. Finally, and most importantly, I will also argue that al-
though coalitionary violence is a primitive feature of human life that
is likely a continuation of the chimpanzee pattern of intergroup rela-
tions, the ability to have peaceful relations with neighboring bands is
a unique derived trait that fundamentally distinguishes chimps from
humans and may have been partially responsible for our rapid cul-
Misrepresenting Evolutionary Theory
Many Rousseauians consistently misrepresent evolutionary ap-
proaches to warfare and violence. This tactic is used because many of
the Hobbesian theorists and researchers take an evolutionary perspec-
tive (Keeley is a notable exception). The argument made is that evo-
lutionists claim humans are inherently or naturally violent because
they have a gene or complex of genes that leads them to be aggres-
sive. Consequently, they conclude that Hobbesians argue that war is
30 (2019) 4
an ineradicable element of human life stemming from human phylog-
eny. Although ethological theorists such as Lorenz (1963) held such an
incorrect view of gene-environment-culture interaction 55 years ago,
this outdated form of biological determinism is fundamentally at odds
with contemporary behavioral ecological or evolutionary psychologi-
cal approaches to individual and collective forms of aggression often
taken by Hobbesians. Just as troubling, many science reporters falsely
associate evolutionary interpretations of violence as representing ex-
amples of “inherent violence” or warfare as “inevitable,” with scream-
ing headlines such as “Is Violence Embedded in Our DNA?” (Gabba-
tiss 2017) or “10,000-Year-Old Massacre Does Not Bolster [The] Claim
That War Is Innate” (Horgan 2016). The problem here is a crude and
warfare as proposed by evolutionary theorists.
Richard Wrangham, a leading evolutionary researcher, is a frequent
target of such critiques and clearly does not take this position when
But the notion that behavioral evolution generates unifor-
mity of behavior is wrong. In any animal species, tendencies
tural norms. So variability of the practice of war is compat-
ible with behavioral evolution (2013a:6).
Behavioral ecological research has repeatedly demonstrated that mam-
mals are opportunistic and strategic, not blind automatons. Instead
the context of their life-historical circumstances and culture. This el-
emental perspective is ignored by Rousseauians.
Minimizing Hunter-Gatherer Violence by Redening
In attempting to understand the frequency and intensity of war
among hunter-gatherers there is some debate on what constitutes a
30 (2019) 5
prototypical hunting-and-gathering society representative of about
95% of our history as a species. According to scholars on both sides
(Bowles 2009; Fry and Söderberg 2013) these societies are residen-
tially mobile, small in size, and egalitarian. In the Standard Cross-
gatherers as societies in which no more than 5%of food resources
comes from domesticated resources. The 35 such societies out of
186 in the SCCS are frequently used to evaluate hypotheses about
hunter-gatherers. In a reexamination of Robert Kelly’s SCCS compar-
ative work (2013) on warfare among hunter-gatherers as well as Em-
ber’s (1978 research, Fry (2006:103–5) argues that equestrian New
World hunter-gatherers such as the Comanche and Chiricahua used
by these researchers should be removed from consideration as pro-
totypical hunter-gatherers because they have composite pastoral and
foraging adaptations making them equestrian hunters. This is reason-
able. Horses, after all, are a domesticated species and are a histori-
cally recent addition to a New World foraging lifestyle. Fry argues that
Yurok and Klamath should also be removed. Such groups have lower
levels of mobility, relatively permanent residences and substantial
ers. Prime examples are groups in the Northwest Coast of North Amer-
defended riverine spots as this crucial resource moves from ocean to
rivers annually to spawn. However, removing them from comparative
analysis may be questionable because we simply do not know enough
about the prehistoric depth of foraging groups with these attributes.
Hopefully, archaeological research will allow us to eventually date the
advent of semi-sedentary hunter-gatherers. Be that as it may, these
groups tend to have defendable or alienable resources (Manson and
Wrangham 1991) and are predicted by behavioral ecological theory to
be likely engage in warfare if only to defend their resources against
others (Dyson-Hudson and Smith 1978). These two general restric-
tions leave Fry and Söderberg with 21 mobile hunting and gathering
societies from the SCCS.
In developing a sample to test hypotheses about the kinds of
hunter-gatherers who have characterized human existence for
95% of our time as a species, the degree and form of contact with
30 (2019) 6
non-hunter-gatherers is a crucial issue. Wrangham and Glowacki
(2012) note numerous problems with Fry’s restricted sample (2007) of
peaceful societies. Following the pattern set by Ferguson’s tribal zone
model (1990), they note that among the “21 nomadic hunter-gatherer
societies listed by Fry (2007) as being peaceful, at least 13 (62%) in-
teracted with pastoralist, farming, or state societies in ways suggest-
ing that they were militarily and/or politically subordinate” (Wrang-
ham and Glowacki 2012:21). That is, they were not hunter-gatherers
interacting with other hunter-gatherers in a context resembling the
EEA. In a response to Wrangham and Glowacki (2012), Fry and Söder-
berg (2014) ignore this critique.
I would single out the relatively peaceful Mbuti and Semang as
prime examples of the problem of hunter-gatherer interaction with
settled horticulturalists that casts doubts on their status as hunter-
gatherers. In many studies of comparative violence (e.g., Keeley 1997;
White (1969) in the establishment of the SCSS, and researchers some-
truly hunter-gatherers or are they what Fox (1969) inelegantly calls
“professional primitives”? That is, can and do they exist indepen-
dently of horticulturalists? Nearly all Pygmy peoples (e.g., Aka, Mbuti,
Efe) are associated with settled Bantu agricultural groups. They trade
wild forest products for agricultural crops and metal goods, and Mbuti
alists. Hart and Hart (1986) estimate that 60% of the Mbuti diet is
from traded agricultural crops. Whether these relationships are based
on political dominance of agriculturalists over Pygmies or a more
egalitarian trade symbiosis seems to vary from place to place (Joiris
2003). This sort of economic exchange and agricultural dependence
is also characteristic of the foraging Semang of the Malay Peninsula
(Rambo 1988) as well. Rambo quotes Schebesta (1929:276) (a PAS,
or principal authority source in Fry and Söderberg’s 2013 sample dis-
cussed below) who states: “[the Semang] live in a kind of symbiosis
with [agricultural Malay and Senoi] villages and settlements, for, in
the jungle.” Underlying both the Mbuti and Semang cases is a debate
about whether a pure hunting-and-gathering existence is possible in
30 (2019) 7
African and Southeast Asian rainforests (Bailey et al. 1989), where
both these groups live. This debate need not concern us here. What is
relevant is whether groups such as the Mbuti and Semang were po-
litically and economically independent hunter-gatherers at the time
data on lethal violence was gathered. My read of the sources suggests
they were not.
Denitions of War
Any estimation of the frequency and intensity of warfare requires a
researchers will simply talk past one another and provide statistics
that may be useless for evaluating descriptive generalizations or iden-
tifying the factors that account for variation in warfare. Some Rous-
large-scale societies while classifying forms of coalitionary violence
in small-scale societies as capital punishment or feud. The common
ber and Ember 1992b:172) is as follows:
or aggregates of communities). In the ethnographic record,
such combat usually involves groups on both sides, but a
warfare event could involve the ambush of a single person
of an enemy or group. Thus, the phrase “socially organized”
means that there is a group of combatants on at least one of
use by other comparative warfare researchers (e.g., Bowles 2009; Ot-
terbein 2004). To make matters a bit more complex, if we turn to an-
other well-known comparative scholar of warfare, Keith Otterbein
(1968:281), we have something called “feud” that appears as a form
of coalitionary violence within a community: “Warfare and feuding
30 (2019) 8
within a political community and warfare as armed combat occurring
tionary groups which are most often families or kinship groups. Nev-
ertheless, feuding, regardless of the motive, is clearly a form of within-
group coalitionary violence.
Fry (2006:88, 172–74) does not consider feuding between commu-
A group activity, carried on by members of one community
against members of another community, in which it is the
which the primary purpose makes it highly likely that seri-
members of that community in the accomplishment of that
substitutability,” in which anyone in a neighboring community is a le-
gitimate target of lethal violence even though the attacking party may
community kills or harms someone in another, members of the com-
trator’s community. Consequently, co-residents are responsible for the
deeds of their community members and are legitimate targets of re-
prisal should one of their own community wrong someone from an-
other community. Clearly, this is a characteristic of the kind of war-
fare found in large-scale societies.
One must ask, what is the utility of distinguishing between various
forms of coalitionary killing and declaring that one type is “true” war,
as do Fry and Raymond Kelly (see Roscoe 2014 for an extended cri-
from war, Kelly does so as to distinguish war from capital punishment.
According to Kelly, capital punishment is a form of socially approved
killing (therefore not murder), targeting a transgressor who has bro-
ken some sort of social norm regardless of whether the malefactor is
30 (2019) 9
a member of one’s community. Whether or not the killing is coalition-
ary is irrelevant. However, “true war” occurs when an entire commu-
nity is found to be liable and therefore worthy of killing because one
of their group has harmed a member of aggrieved group. It repre-
sents collective responsibility that focuses on the corporate nature of
that war was rare or absent among a large number of what he calls
non-segmentary hunter-gatherers even though coalitionary killings
between groups occur. Non-segmentary hunter-gatherers are those
who lack, among other things, descent groups and preferential mar-
riage rules. Kelly (2002:123) without explanation, even goes so far
as to deny that war occurs between chimpanzee bands, even though
chimps target any individual in a neighboring band, when he states,
“pongicide (apes killing one another) is an analogue of homicide and
both are undoubtedly ancient. However, chimpanzees lack both capi-
tal punishment and war.”
the case of capital punishment or group responsibility in the case of
damental in any evolutionary analysis. We do not know much about
chimpanzee culture or what is going on inside the mind of a chim-
panzee or any other species that we might compare with humans. Al-
though we can infer function or motivation for chimpanzee warfare
in terms of group residence and coalitionary lethal interactions be-
war used by Ember and Ember and followed by most cross-cultural
researchers, including archaeologists, motivation or social acceptabil-
ply that coalitionary killing has become more complex and organized
through time. Humans and chimps engage in between-group coalition-
ary killing by targeting individuals who are members of other residen-
tial groups. As groups become more corporate, often through descent
group organization, members cooperate and share rights and duties
in the political arena (Fried 1957). They jointly defend one another
and take lethal action on other groups. They become more strongly
30 (2019) 10
united for certain purposes, including collective responsibilities for
their members. Such groups also have the ability to stop war by us-
by Kelly allows them to claim war is relatively new and more com-
mon today than in the past, even though between-group coalitionary
killings are an ancient human practice shared with chimpanzees, our
last common ancestor, and hominins (Kissel and Kim 2019). What
Kelly (2002:52, Table 4) has documented in his distinction between
segmentary and nonsegmentary bands is that some hunter-gatherer
bands are more corporately organized in their pursuit of war.
Censoring Ethnographic Reports and Lethal Events
As part of a special edition of journal Science entitled “Human Con-
of lethal aggression events among mobile foraging bands. The main
results of their analysis are portrayed in their Fig. 1, a bar chart show-
ing counts of individual and collective acts of lethal violence in a sam-
ple of 21 mobile foraging bands winnowed, as noted earlier, from the
SCCS. Their Table 1 provides a breakdown of these events by “Reason.”
of lethal aggression among MFBS [mobile foraging band societies]
as war” (Fry and Söderberg 2013:270). To some extent, this is a use-
ful approach because previous comparative data did not distinguish
between homicides and warfare in causes of death (e.g., Keeley 1997;
Knauft 1987). The goal of these earlier surveys was to measure the
probability of being killed by another human whether through homi-
cide or war to assess the demographic impact of lethal violence. With-
war was more common than homicide. Comparative research on ho-
micide and warfare shows a positive correlation between frequency
of homicide and assault on one hand and the frequency of warfare in
sures were rank-ordered and referred to frequency (e.g., common ver-
sus uncommon) and not to intensity (e.g., deaths per 100,000/year).
30 (2019) 11
This being said, the statistical and methodological problems with Fry
and Söderberg’s generation of the descriptive data sharply limit their
generalizations and conclusions. I will deal with the methodological
Methodologically, the data sources used in the survey are censored
through the use of Principal Authority Sources (PAS) in their sample
of 21 hunting and gathering societies from the SCCS. These sources, as
determined by Douglas White (1989), who created the standard, are
argued to be the earliest reliable ethnographic sources for societies
in the SCSS. Researchers use the SCCS as a sampling frame because
it contains a common set of preindustrial societies scattered about
the globe in an attempt to come close to an independent sample. This
sampling frame has been the source of hundreds of comparative stud-
ies. Nevertheless, one is not required to use PAS sources when doing
comparative research. Fry and Söderberg did so:
To circumvent sampling bias, rather than self-selecting cases,
we derived the sample of MFBS based on the published rat-
ing criteria of other researchers. During data collection, we
used only the principal authority sources (PAS) as the ear-
liest, high-quality ethnographic descriptions available (Fry
and Söderberg 2013:279).
This selection criterion poses a problem that leads to their results
being an artifact of this restrictive set of sources by censoring po-
tentially reliable non-PAS sources in their sample. The problem with
some early, high-quality PAS sources is that some may contain little
rich and extensive information on standard ethnological topics, such
as family, marriage, and religion. Another problem with their strict
reliance on PAS is that some of their sources describe lethal events
that are clearly a post-contact phenomena. Their PAS sources include
cases of “execution of outsiders (such as missionaries, explorers, cast-
aways, and colonists)” (in their online Table S3:23). If their goal is
to evaluate claims that that “chronic raiding and feuding character-
ize life in a state of nature,” or that hunter-gatherer “war deaths are
substantial in recent millennia and in the Pleistocene” (Fry and Söder-
berg 2013:272), then documentation of lethal events of or by modern
30 (2019) 12
deaths. Ironically, Fry (2013:13) strongly criticizes Bowles’s (2009) use
of Hiwi and Ache deaths from warfare because nearly all those deaths
were at the hands of modern ranchers and other colonists.
The case study approach used by Fry and Söderberg may also hide
the overall assessment of the frequency of violence. If a PAS ethnog-
warfare is frequent, exacts a heavy toll on human life, and talks about
displacement with only a few case studies, then a society can be shown
to have few lethal events. Of course, the strength of the case study ap-
proach of Fry and Söderberg is that one can gain rich details on the
causes and consequences of lethal violence. In the end, it is up to a re-
searcher to select those sources she or he believes to be reliable and
accurate, and by citing those sources in requisite detail to allow oth-
ers to evaluate the quality of those sources. I will use examples of the
Andaman Islanders and the !Kung in Fry and Söderberg’s sample to
illustrate the problem of censoring.
In “Warless Societies and the Origins of War” (2002), ethnologist
Raymond Kelly details lethal violence among hunter-gatherers in the
Andaman Islands. Therein he notes 13 lethal raids between Bea and
Jarawa (Kelly 2002:100), with the Jarawa geographically displacing
the Bea through warfare. In doing so, he relies on what he believes to
be reliable historical accounts of British colonial authorities, such as
Portman (1899). The two instances of lethal events for the Andaman
Islanders in Fry and Söderberg’s Fig. 1 (2013) is clearly discrepant.
A further example of the problematic use of PAS sources is seen
in Richard B. Lee’s masterful work on the !Kung (1979) wherein he
describes 22 case studies of homicide, yet Fry and Söderberg’s data
(2013:271, displayed in their Fig. 1) show but four cases because Lee’s
work was not in the PAS. However, D. White in his PAS article clas-
was increased to 84 (Wiessner 2016), although many of the newly
recorded deaths are clearly the consequence of alcoholism and other
better characterize the nature and causes of! Kung interpersonal vi-
olence, that information is not represented in their Fig. 1 from which
their major conclusions on mobile foragers’ lethal events are drawn.
30 (2019) 13
The two statistical problems involve demographically uncontextu-
alized events and using “lethal events” as a measure without count-
ing the number of deaths in each lethal event. The data shown in their
Fig. 1 and Table 1 (2013:272) are raw counts of lethal events without
cult to interpret within their sample or cross-culturally. That is, the
counts have no denominator to control for time frame or population.
In comparing rates of violence the standard is to provide deaths per
100,000 per year or proportion of causes of deaths as a consequence
of violence (e.g., Bowles 2009), allowing a population-based compar-
ative perspective. The earliest tally of deaths through violence from
Knauft (1987) through Keeley (1997) to more recent tallies combining
a variety of sources (Roser 2018) use these contextualized measures.
The second statistical problem involves counting lethal events with-
out counting the number who died in those events. Fry and Söder-
berg’s measure of violence as a “lethal aggression event” is useful
for gaining a sense of how common various types of lethal events oc-
cur, such as “intergroup events” or “interpersonal events,” and rep-
resents a noteworthy contribution to the literature. In their Table 1
used by comparative researchers. However, the number of events does
not fully measure the impact of violence. Evolutionary theorists argue
(e.g., Bowles 2009) that the demographic impact of war measured as
the proportion of violent deaths is the critical measure of the impor-
tance of war from an evolutionary perspective. Even those who do not
take an evolutionary perspective, such as Keeley (1997:88), regard this
measure as fundamental for understanding the demographic impor-
tance of warfare. Using lethal events would be like a biogeographer
using number of rain events to predict biomass patterns across land-
scapes instead of centimeters of rain per year.
Fortunately, Fry and Söderberg (2013) provide data on number of
deaths for each “lethal aggression event.” I reanalyzed the data pro-
vided in their online supplementary data (Table S4), where “number
killed” was associated with “relationship” between “Killer(s)” and
“Victim(s).” Unfortunately, in the “relationship” column for 18 of the
30 (2019) 14
of within- or between-group killings. I then grouped number killed,
as best I could into within-group and between-group deaths: within-
group deaths mean that the killing took place within the same resi-
dential group and between-group deaths were killings that occurred
between residential groups. Of the useable 116 cases of lethal events,
59 deaths (or 50.8%) were between-group deaths and 57 (or 49.1%)
were within-group deaths. Note that a massacre among the Vedda ac-
counted for 25 of these killings (Fry and Söderberg estimate between
20 and 30 deaths, so I took the middle value of 25 in my reanalysis).
Although Fry and Söderberg show that within-group lethal events are
more common than between-group lethal events (66% vs. 33%, re-
spectively), death counts from warfare and within-group homicides
were nearly equal in terms of total killed.
It is perhaps more important to point out that Fry and Söderberg’s
search. Ember and Ember (1997:7, Fig. 1.1), using the SCCS, show
that on average, hunter-gatherers have the lowest frequency of war
(“war occurs once every two years or so”) compared with horticultur-
alists, intensive agriculturalists, and pastoralists, among whom war,
on average, occurs “every year in a season.” This result generally co-
ing the intensity of violent death is lower among hunter-gatherers (at
200 per 100,000/year) than “farmers” (at 600 per 100,000/year). It
is possible that the hunter-gatherer estimates may be higher prior to
existential terms can be calculated in terms of the proportion of all
deaths as a consequence of war. For hunter-gatherers, Bowles (2009),
using a sample of 8 ethnographically described hunter-gatherers and
15 from the archaeological record, found that the fractions of adult
mortality resulting from warfare were approximately equal at 14%.
Max Roser (2018) has assembled a very comprehensive online lethal
violence data base of anthropological and archaeological studies using
published sources that began to accumulate after Knauft (1987) made
his path-breaking start. I downloaded his “Share of violent deaths for
warfare and other forms of lethal violence for an ethnographic sam-
ple that I divided into 7 hunter-gatherers and 18 horticulturalists. The
30 (2019) 15
adult violence mortality percentages were 12% for hunter-gatherers
t p = 0.016; see Fig. 1).
Trends in Lethal Violence
The general trend documented by Keeley is that the demographic im-
pact of war declined with the evolution of the state. Percent of popu-
lation killed per annum is much lower (5 to 40 times lower) in state
societies (1995:89, Fig. 6.1) than in non-state societies. The same pat-
tern emerges in warfare deaths as a percentage of all causes of death
(1995:90, Fig. 6.2). Within that range of social and economic com-
and here (Fig. 1) indicates a doubling or tripling of warfare intensity
among “farmers” relative to hunter-gatherers even though these rates
sharply decline in state-level societies (Keeley 1995). Closer inspec-
tion of the societies in the Wrangham et al. data set and here indi-
cates two things. First, the so-called farmers in Fig. 1 range from sim-
ple slash-and-burn horticulturalists to rainfall agriculturalists, all of
whom lack draft animals, the plow, and other means of technological
Fig. 1. Percent mortality from lethal violence by subsistence type
30 (2019) 16
these societies, especially those in Amazonia, depend heavily on for-
aged resources (Hames 1989). Second, these “farmers” are associated
with headman (or big-man) political organization and not chiefdom-
level societies governed by hereditary chiefs. At this point we do not
understand the causes of this now well-documented uptick in war in
subsistence regimes moving from hunter-gatherers to simple horti-
culturalists and/or how war intensity may have changed from egali-
tarian societies to more hierarchically organized big man societies to
centralized chiefdom and early state-level societies.
Tribal Zone Theory
Tribal zone theory is a historical approach that focuses on how the
frequency, and nature of warfare in small-scale societies. As colonial
forces moved into indigenous tribal areas they engaged in territorial
appropriation, trade, warfare, slaving, resource extraction, and intro-
duced devastating diseases. In the process they also displaced groups,
oftentimes forcing them into areas occupied by other tribal peoples
and leading to an initiation or increase in intertribal warfare (Fergu-
son and Whitehead 1991). A classic example of this approach is found
Secoy’s (1953) account of historical warfare on the Great Plains in
North America. Access to horses and guns through the fur trade along
with colonial displacement led to a dramatic increase in warfare in
the North American Plains as well as in the Southwest. Colonists also
sometimes employed indigenous peoples as mercenaries against other
indigenous peoples. Tribal zone theorists do not claim that warfare
and other forms of violence did not exist prior to colonization (Fergu-
son and Whitehead 1991). Ferguson emphasizes that accounts of tribal
warfare by explorers, colonial administrators, early ethnographers,
and traders have been used by ethnologists in comparative studies of
the intensity and frequency of warfare without placing these accounts
in their proper historical perspective.
In a series of publications, Ember and Ember (1992a, 1997, 2001)
have put the tribal zone hypothesis to test by examining warfare
30 (2019) 17
the time at which external powers imposed administrative control
on the people they invaded (Ember and Ember 1992b:169–71). They
then compared the frequency of warfare combining all sources (be-
warfare coded as “absent or rare” went from 27.6% in the overall
end, warfare coded as “constant or any time” went from 38% in the
1997:5). One of the reasons they used this division was to “distin-
guish the truly more peaceful societies from the societies that had
had peace imposed upon them” (Ember and Ember 1992b:169). We
aligns with Ferguson’s emphasis on historical context, is that his-
tribal war by increasing its frequency and intensity. Second, colo-
nial contact much more generally decreases the frequency of war-
fare, which is the opposite of Ferguson’s historical perspective that
contact tends to increase the frequency of warfare.
As noted above, the perspective in tribal zone theory is similar to
Power’s (2005) claim that chimpanzee violence is a consequence of
trade, and agricultural intrusions and is not adaptive. Comparative
data from 22 chimpanzee study sites by 30 researchers (Wilson et al.
2014), however, provides clear evidence that chimpanzee violence is
not caused by human contact or other unnatural conditions. As might
be expected, Ferguson, the leading proponent of tribal zone theory, is
developing a critique of the comparative research on chimpanzee war-
fare in all its historical complexity currently entitled “Chimpanzees,
War, and History: Are Men Born to Kill?” (https://www.researchgate.
; also see Ferguson 2014). Note the sub-
title suggests that he may claim that Hobbesians believe human kill-
ing is coded in genes and is inevitable. (For an examination of Fer-
guson’s shifting position see Gat 2015:113, and see Wilson 2014 for a
point-by-point rebuttal of Ferguson’s critique.)
30 (2019) 18
Archaeology, Agriculture, and Warfare
Based on archaeological evidence, Haas (2001; Haas and Piscitelli
2013) makes two arguments about the antiquity of war: (1) prior
to the invention of agriculture 10,000 years ago there is scant evi-
dence of warfare in the archaeological record and (2) contemporary
or ethnographic accounts of warfare among hunter-gatherers can-
not be used to inform the past history of violence because expansion
by farmers and later colonial empires disrupted hunter-gatherer so-
ciety. It is quite true that there is little evidence of warfare prior to
the 10,000-year date of the transition to agriculture (but see Wen-
dorf 1968 and Mirazón Lahr et al. 2016 on archaeological evidence of
hunter-gatherer war prior to this date). To a great extent this lack of
archaeology of hunter-gatherers and farmers (Wilson 2013). As de-
tailed by Bamforth (2018) and many others, compared with hunter-
gatherers, agriculturalists are more sedentary; exist at higher den-
create larger middens; and oftentimes have cemeteries near their set-
tlements. Finally, the older the site, the more likely that taphonomic
processes (e.g., erosion) will destroy, obscure, or dramatically alter a
site. Consequently, more recent archaeological remains of sedentary
people are much more likely to be preserved and encountered by ar-
chaeologists than those of earlier hunter-gatherers who leave a light
imprint on the landscape.
More to the point, the use of the “prior to 10,000 year mark” by
Haas and Piscitelli (2013) is deceptive for a number of reasons. It
is true that agriculture originated in the Middle East about 10,000
years ago (Bar-Yosef 2017), but it developed much later in other
parts of the world, and never developed in other places, such as Aus-
tralia, prior to recent European colonization. At the base of their
argument is the general claim that ethnographic and historical ac-
counts of hunter-gatherers are tainted by contact with agricultural-
ists. This contact led to an increase in warfare as a consequence of
agricultural expansion into hunter-gatherer lands and is consonant
with the tribal zone perspective of Ferguson (1990). Although ag-
riculturalists can dominate the political and social lives of hunter-
gatherers through trade and intermarriage (e.g., Headland and Bailey
30 (2019) 19
1991), this position lacks archaeological and historic credibility out-
side of Europe and the Middle East (but see Gat 2015 on Old World
warfare). More to the point, it is a red herring. There is considerable
archaeological evidence of high levels of lethal violence and war-
fare among hunter-gatherers in Native North America (Schwitalla
et al. 2014) without contact with agriculturalists. In Australia (Par-
doe 2014), agriculture was completely absent until 1788 when the
by Allen and Jones (2014) provides archaeological surveys and case
studies of intense warfare among North American and Australian
hunter-gatherers in the absence of contact with agriculturalists (see
also Lambert 2002 for a classic survey of North America). Research
of the tremendous amount of skeletal evidence of lethal trauma in
areas far from agricultural centers (Allen et al. 2016). And in Aus-
tralia, archaeological evidence as well as historical and ethnohistoric
evidence document frequent warfare from ecologically rich drain-
ages such as the Murray River as well as resource- poor desert ar-
eas as well (Allen 2014b). Although Haas’s 10,000- year mark may
be relevant in certain Old World contexts, it is completely irrelevant
for other parts of the world.
War Is a Chimpanzee Invention and Peace Is a Human Invention
A key element in the distinctive evolution of human society is the de-
velopment of peaceful relations between residential groups (Rodseth
and Wrangham 2004; Rodseth et al. 1991), or what Chapais (2010:41–
1940, Margaret Mead claimed that “Warfare Is Only an Invention—
Not a Biological Necessity” (cited in Gat 2015:123). Whether or not
war is a cultural invention boils down to unproductive semantics. The
subtext of Mead’s statement is that war is simply an arbitrary cul-
tural invention and not a part of human nature. Consequently, there
is hope for an end to war. From an evolutionary biological perspec-
tive, war and peace are simply human capacities that are elicited un-
to promote peace.
30 (2019) 20
What is lost in this semantic debate is that from a phylogenetic per-
spective it is clear that peaceful relations between human residential
from chimpanzees and perhaps our last common ancestor. Chapais
(2009:232–33) in Primeval Kinship traces the evolution of phylogenet-
ically derived human social characteristics such as relatively durable
pair bonds in the context of multi-male mixed-sex groups. He recog-
nizes that “peace prevailed at the intratribal level (between bands), but
not at the intertribal level” and hence that “the tribe did not eliminate
intergroup hostility but brought about a major change in the level of
social structure at which hostility was taking place.” This fact is typ-
ically ignored in the discussion of the evolution of human warfare by
both camps. Unlike chimps, hunter-gatherers can have peaceful rela-
tionships with neighboring bands that include prolonged visits by fami-
lies, marriage, trade, and resource sharing in times of need. For the past
century and in various ways this wholly distinctive human feature has
been recognized by major social theorists such as Edward Tylor, Leslie
White, and Claude Lévi-Strauss (Rodseth et al. 1991) in studies of inter-
band marriages. Among chimpanzees, neighboring groups are territorial
and between-group encounters range from avoidance with occasional
lone individuals or small groups who are numerically outnumbered by
mented by Goodall (1986), one group may exterminate another and take
over its territory. However, among bonobos relations between neigh-
boring groups are generally benign. Despite long-term observation at
many sites, there is no sure evidence of intragroup or intergroup kill-
ings. When bonobo bands meet in border areas, interactions range from
noisy agonistic displays to relatively tense but peaceful minglings, in-
cluding co-nesting (Pisor and Surbeck 2017), and even food sharing
along with a high degree of social tolerance between groups (Fruth and
Hohmann 2018). However, nearly all these interactions last no longer
than a day or so and groups part with no exchange of individuals. Upon
sexual maturity, chimp and bonobo females, but not males, join neigh-
boring groups; they lose contact with their natal band and they do not
return. It is fair to say that bonobos have peaceful inter-band interac-
tions but they lack systematic social intercourse and partial, relatively
long-term fusions among neighboring bands or band members.
30 (2019) 21
Chimp and bonobo separatism is in sharp contrast to humans. Hu-
man bands typically have peaceful relations with their neighbors even
though war may occur. The hunter-gatherer literature abundantly de-
scribes intergroup visiting between members of distinct residential
some instances individuals or families may take up semi-permanent
to permanent residence in neighboring bands. These interactions en-
compass trade, visiting relatives, ceremonies, and aggregations around
dense seasonal resources (Layton et al. 2012). For example, among the
Gwi Bushmen “Not only do individual families visit neighboring res-
idential bands but an entire band may move into the territory of an-
other during times of plenty for festive purposes and may also tem-
porarily join another when local resources are scarce so long as they
have the permission of their neighbors” (Silberbauer 1972:296–97).
Both Layton et al. (2012) and Chapais (2010) characterize hunter-
gatherer social organization as multilevel such that local residential
bands are linked to other bands through a variety of ties, creating a re-
gional band structure (see also Wilson and Glowacki 2017:486). This
settlement pattern has been recognized using terms such as macro
band, ethnolinguistic unit, and regional band to encompass entities
within which marriage, trade, and so on, can peaceably occur (e.g.,
Damas 1969). Following Helm (1965), I use the term “band” or “local
band” to characterize an entity that lives together most of the year
ilies or task groups separate during the year only to reaggregate on
a regular basis. A regional band is composed of local bands who of-
ten interact peaceably and speak a common language. Layton et al.
(2012:1217–19, Table 1) provide demographic characteristics for 26
hunter-gatherer societies that comprise local and regional bands (or
gregation of bands between which individuals can move with a mini-
mum of formality, within which most marriages take place and that is
frequently characterized by a distinct dialect or language (2012:1221).
bands, and total regional band size is about 250–500. Using a larger
sample, Binford (2002) uses the term “ethnolinguistic unit” instead of
regional band, and with a much larger data base he calculates a mean
of 839 inhabitants for regional bands and a mean local band size of 54.
30 (2019) 22
This is not to say that local bands within a regional band do not en-
gage in internal warfare. They do, and how often this occurs is a mat-
ter for empirical research. It is also probable that relations between
regional bands tend to be more hostile, and external war (war be-
(e.g., Burch 1974, 2005). Comparative research by Walker and Bailey
(2013) using a combination of hunter-gatherers and foraging horti-
culturalists from lowland South America shows that although internal
war is more frequent than external war, external war is more deadly.
friendly relations through various forms of peaceful social intercourse.
From a phylogenetic perspective, between-band coalitionary vi-
olence or warfare may be a primitive or ancestral trait in humans
shared with chimpanzees and perhaps our last common ancestor,
whereas variable peaceful relations between human bands in a re-
gion is a derived trait. Other primitive traits we share with chimps
may include reconciliation, sympathy, consolation, kin altruism, and
perhaps reciprocal altruism (de Waal 2010; Silk and Boyd 2010). In
a number of publications, Boehm (e.g., 1993) sketches the evolution
of primitive and derived traits in humans and chimps that relate to
use coalitions to battle for dominance (de Waal 2010) and later rec-
als and coalitions. Boehm’s (2012) so-called reverse dominance hier-
archies arose in humans to check the dominance of alpha males and
their allies leading to a lower reproductive skew. How this arose is
didate (Gintis et al. 2015).
The ability of hunter-gatherer bands to peacefully coexist with
be an elaboration of bonobo intergroup relations. This is something
that Rousseauians and Hobbesians ought to recognize in their debates
about the nature of coalitionary violence. This derived trait may have
been crucial for the spread and elaboration of culture (Hill et al. 2014).
30 (2019) 23
For example, Layton et al. (2012) estimate that human communities
panzee bands. Peaceful and regular interaction between local bands
permits the sharing of important discoveries vital to survival, such as
food processing techniques, tool innovations, and traditional ecologi-
cal knowledge (Henrich 2004). For example, primatologists have ar-
gued that the impoverished tool repertoire of orangutans relative to
chimps (Fox et al. 2004) is a consequence of social group size that af-
fects the rate of adaptive innovations.
Is War Adaptive?
Rousseauians argue that warfare is not evolutionarily adaptive for em-
pirical and apparently political reasons. Denial of the antiquity and
tion it will either condemn us to perpetual violence or diminish our
attempts to prevent war (Fry 2006:234–38; Sussman and Marshack
2010; see Wrangham 2013b for a response). This sort of political ar-
gument is irrelevant: the answer to the question of whether war is
adaptive can only be answered with empirical research and not moral
alarm about the consequences of such knowledge.
ing, and the observation that killing is an exceptional event in hu-
man societies leads to the counterhypothesis that lethal behavior has
been strongly selected against, not favored, in comparison to more re-
or not a certain kind of behavior is common or exceptional is much
havior. Fig. 1 shows human violence is a major cause of death in small
scale societies, especially for males even though it may be “an ex-
ceptional event.” At the individual level of selection, Chagnon (1988)
demonstrated that Yanomamö warriors known as unokais (those who
had killed enemies) had greater reproductive success than those who
had not. Among Nyangatom herders on the Ethiopian-Sudan border,
Glowacki and Wrangham (2015) provide evidence that elders who
30 (2019) 24
eight Yanomamö villages, Chagnon reports that 11–17% of all mar-
ried women were forcibly abducted from neighboring villages by mil-
itarily more powerful groups (Chagnon 1997:88, Table 2.1). In their
survey of warfare in the 186-society SCCS sample, Ember and Em-
ber (1992a) show that, in 73% of cases, victors sometimes drove van-
quished from their lands, and in 90% of the cases, victors took trans-
portable resources (e.g., domesticated animals and crop stores). In
contrast, Beckerman and colleagues’ (Beckerman et al. 2009) research
on the Waorani, an Ecuadorian group much like the Yanomamö, found
a negative relationship between zealous (those who frequently raided)
and non-zealous warriors in terms of reproductive success. Impor-
tantly, Beckerman et al. argued that the Waorani were warring them-
selves into demographic decline because a large fraction of deaths
were women. Clearly much more work is needed in this area that may
A unique characteristic of human warfare meriting better under-
standing is revenge, a phenomenon noted by many (see Gat 2000 for
an evolutionary analysis of revenge and Beckerman and Valentine
2008 for case studies in Amazonia). Walker and Bailey (2013) sur-
veyed warfare and homicides in 11 pre-contact lowland South Ameri-
can societies totaling 1281 deaths. Revenge was the motivation in 70%
of these killings. Furthermore, they concluded, “The average percent
of violent deaths across all 11 studies is 30% indicating that violence
was probably a potent selective pressure for many traditional societ-
ies” (2013:31). In standard evolutionary approaches to violence the fo-
cus is on reproductive advantage through acquisition of food-related
resources or mates. How revenge may be explained with evolution-
ary logic is a major challenge. It is perhaps the case that a posture
for revenge, for previous attacks or supernatural depredations (e.g.,
sorcery accusations), may lead to deterrence or motivate resource or
I have argued that Rousseauians have used a variety of tactics to di-
30 (2019) 25
evidence of war among hunter-gatherers, censoring sources, and fo-
cusing on the frequency of warfare while ignoring the demographic
consequences of warfare. Researchers who take an evolutionary ap-
proach to human warfare generally take a Hobbesian approach by
arguing that warfare has a deep human history and has played a
empirically established that war is less frequent among hunter-gather-
ers than among more intensive economic formations (Ember and Em-
ber 1997) and the mortality rate for violence among hunter-gatherers
is lower relative to that of agriculturalists (Wrangham et al. 2006). In
response to tribal zone theorists and others, Ember shows that even
erers and equestrian hunter-gatherers, warfare is rare or absent in
only 12% of her sample of mobile hunter-gatherers (Ember 1978:443).
There are at least two outstanding problem in the evolution of war-
fare we ought to address. How do we account for the tremendous up-
surge in war deaths, on a per capita basis as we move from egalitar-
ian to semi-egalitarian horticultural groups, only to decrease sharply
with the advent of the state? Another issue is how to make sense of
revenge as a cause of war, which seems to be absent in chimpanzees
but common in humans.
At this point, the positions taken by Wiessner and Robert Kelly are
the ones we ought to follow. In an interview by Culotta (2013:224)
accompanying the Fry and Söderberg (2013) piece in Science, Wiess-
ing what promotes and what inhibits warfare” and “We should be ask-
ing how coalitionary aggression, which does appear in our phylog-
eny, was harnessed among our successful ancestors.” A similar view
is stated by Robert Kelly: “the better question is: when do foragers re-
sort to war?” (2013:158).
We have made some progress in understanding war for both hu-
mans and Pan
Likewise, to understand variation in warfare among hunter-gatherers
we have cross-cultural statistical analyses that point to resource com-
petition, such as Ember and Ember’s (1992b) resource unpredictabil-
ity and Kelly (2013) on population density. Manson and Wrangham
30 (2019) 26
(1991) point to the presence or absence of alienable resources as de-
termining whether resources or mates will be targets in warfare. One
of the problems faced by comparative researchers is an overreliance
on the 35 hunter-gatherers societies in the SCCS or Fry and Söder-
berg’s (2013) exclusions to reduce the sample to 21. Use of the SCCS
as a sampling frame was designed to overcome what is known as Gal-
2008). One way around this problem is to use phylogenetic compar-
ative methods (e.g., Mace et al. 1994) to control for common ances-
try in order to test for functional relationships on the causes of war-
fare. This method is gaining acceptance in cross-cultural research.
Using this method would allow us to take advantage of a much larger
data base, such as Binford’s Constructing Frames of Reference (2002),
which contains information on more than 300 hunter-gatherer soci-
eties. Finally, archaeological data on recent hunter-gatherers largely
isolated from non-hunter-gatherer societies, such as the Central Cal-
ifornia Bioarchaeological Database (Pilloud et al. 2014), may lead to
new insights. By following these avenues we would then be in a much
better position to identify the factors that promote war and peace
Acknowledgments — I thank Phil Geib, Azar Gat, Bernard Chapais, three
anonymous reviewers and especially Michael Wilson for their careful read-
ing and useful comments on the manuscript. I also would like to thank my
research assistant Victoria Salinas for her tabulations of the SOI data in Fry
and Söderberg (2013).
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Raymond Hames is a professor of anthropology at the Univer-
sity of Nebraska–Lincoln. He received doctorate in anthropol-
ogy from the University of California-Santa Barbara in 1978. His
zon (Yanomamö and Ye’kwana) with funding from the NSF, LSB
Leakey Foundation, and Harry Frank Guggenheim Foundation. His
research interests are in behavioral ecology, food and labor ex-
change, human ecology and conservation, marriage, kinship, and