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37
Natural Born Nonkillers
A Critique of the Killers-Have-More-Kids Idea
Marta Miklikowska
Åbo Akademi University
Douglas P. Fry
Åbo Akademi University and University of Arizona
There is an oft-voiced proposition within evolutionary psychology that over
the course of evolutionary time, natural selection favored human males who
have killed over those men who have not. The implication is that killing has
been favorably selected as a fitness enhancing strategy. Interestingly, the impe-
tus for this proposition in large part stems from one particular article on the
tribal Yanomamö people of Brazil and Venezuela published in 1988. In this arti-
cle, Chagnon (1988) reports that Yanomamö men who have participated in a
killing out-reproduced their same-aged peers. If a Yanomamö man participates in
a killing, he must undergo a purification ritual and henceforth wears the cultural
label
unokai
. In a series of publications, Chagnon (1990: 95, 1992a: 205, 1992b:
239-240; see also Chagnon, 2010) reiterated that
unokais
average more than
two-and-half times the number of wives and more than three times the number
of offspring as non-
unokais
of the same age
.
Pinker (2002: 116) concludes that
“if that payoff was typical of the pre-state societies in which humans evolved,
the strategic use of violence would have been selected over evolutionary time.”
A careful re-examination of the Yanomamö
unokai
findings and the infer-
ences that have been drawn from them are important because they have been
broadcast far-and-wide and have been uncritically accepted within evolutionary
psychology and other fields. For example, Buss discusses the
unokai
reproduc-
tive success findings in
Evolutionary Psychology
(1999) and again in
The Mur-
derer Next Door
(2005: 35): “Humans have evolved powerful psychological
adaptations that impel us to murder as a means for solving specific problems we
encounter during the evolutionary battles for survival and reproduction.” Harris
relates the killers-have-more-offspring finding in
The Nurture Assumption
. In
U.S. News and World Report
, a journalist proposed that Chagnon’s study
“lends new credence” to the idea that “war arises from individuals struggling for
reproductive success” (Allman, 1988: 57). Pinker reiterates the findings in
How
the Mind Works
(1997) and again in
The Blank Slate
(2002).
38 Nonkilling Psychology
Since Chagnon (1983), Buss (1999), and others view the Yanomamö as a
living diorama of humanity’s ancestral past, then it follows by this reasoning that
humans are descendents of natural born killers. The basic evolutionary logic
runs as follows. There is variability in a population: Some men are killers and
some are not. Certain individuals out-reproduce their neighbors, and, based on
the Yanomamö study, killers appear to have more offspring. Traits, such as kill-
ing, are to some degree heritable and thus can be passed to succeeding genera-
tions. Therefore, humans have evolved to be natural born killers.
In this chapter, we will argue that this dramatic interpretation of human
nature is probably 180 degrees off course and that the killers-have-more-
kids proposal is unfounded for a variety of reasons. First, computer simula-
tions of evolutionary processes suggest that killing as an aggressive strategy
would have been selected against, not favored, by natural selection. Second,
the idea that lethal aggression has been evolutionarily favored in humans
runs counter to a substantial body of contextualizing data on animal behav-
ior that shows intraspecific killing to be the exception, not the rule, in the
animal kingdom. Third, military science and anthropology suggest that hu-
mans have an evolved psychological aversion to killing, not a psychological
adaptation that impels them to kill. Fourth, psycho-social models regarding
the socialization and social learning of values related to killing and nonkilling
reflect the observed cultural variation in these behaviors, whereas the idea
of an evolved propensity for killing is hard-put to account for such variation.
Fifth, the original study (Chagnon, 1988) has multiple analytical flaws that
call into serious doubt the conclusion that Yanomamö killers have over
three times the number of children as nonkillers. Sixth, two other studies,
on the Waorani and Cheyenne (Beckerman, Erickson, Yost, Regalado,
Jaramillo, Sparks, Iromenga and Long, 2009; Moore, 1990), report findings
opposite to those published for the Yanomamö by Chagnon (1988).
Computer Simulations of Evolutionary Processes
Game theory simulations of the evolutionary process provide us with a
hawk-dove
model, which, although simple, offers some tantalizing insights.
Maynard Smith and Price (1973; Maynard Smith, 1974) use computer simu-
lations to model the evolution of aggression by comparing the relative suc-
cess of different fighting strategies. They use the term
evolutionary stable
strategy
for a particular behavioral pattern, that “if most of the members of
a population adopt it, there is no ‘mutant’ strategy that would give higher
Neurobiological and Evolutionary Perspectives on Nonkilling 39
reproductive fitness” (Maynard Smith and Price, 1973: 15). An evolutionary
stable strategy is roughly comparable to a behavioral adaptation.
The researchers discovered that neither belligerent (hawk) nor timid
(dove) strategies are as evolutionarily successful as a strategy they call the
re-
taliator
strategy. This approach to social interaction entails being nonaggressive
unless attacked, at which point a retaliator fights back. In the computer simula-
tions, timid individuals that retreated did not fare very well compared to more
aggressive individuals; however, fighting entails risks of injury and therefore
overly-aggressive individuals also accumulated evolutionary costs. The conclu-
sion from such simulations is that the agonistic strategies that fare the best are
those that are limited and restrained, not lethal ones. Restrained aggression is
more advantageous to fitness than either pure dove or pure hawk strategies
(Archer, 1988; Archer and Huntingford, 1994; Riechert, 1998).
Restrained Patterns of Competition: The Animal Data
In making a cross-species generalization, ethologist Hinde (1974: 268) con-
cludes that among animals, “death and injury are less common than might be
expected.” In fact, most intraspecific aggression in the animal kingdom is
nonlethal (Alcock, 2005; Kokko, 2008; Maynard Smith and Price 1973). None-
theless, escalated fighting can lead to fatal injuries, for example, as has been
reported among chimpanzees, hyenas, and lions (Alcock, 2005; Schaller, 1972;
Wilson, 1975: 246). Also, there are some special cases where the cost-to-
benefit ratio of killing tips the balance in favor of killing. For instance, the mat-
ing system among langur monkeys consists of social groups with a single male
and a harem of females with whom the male mates until he is deposed and re-
placed by a new male (Hrdy, 1977). After a series of fights to gain mating rights
over a harem, a new male often attempts to kill young infants that were sired
by the previous male (Hrdy, 1977). On the cost side, an adult male langur does
not place himself in much risk of injury by attempting to kill an infant, although
the infant’s mother or other female relatives may attempt to protect an infant
from an infanticidal male. On the benefit side, an infanticidal male langur may
be able to reproduce sooner than if a male allows his predecessor’s infants to
live, because the mothers of killed infants will come into estrus and be able to
conceive during matings with the new male sooner than if they had continued
lactating and nursing the infants fathered by the prior male (Hrdy, 1977).
So in some special cases, like langur infanticide, killing does occur in the
animal kingdom and conveys evolutionary benefits. However, such cases are
exceptional and represent situations where the fitness pay-offs to the killer
40 Nonkilling Psychology
outweigh the risks to the killer. For the most part, however, animal studies
show a recurring pattern wherein aggression against conspecific rivals is limited,
restrained, and rarely lethal (Archer and Huntingford, 1994; Eibl-Eibesfeldt,
1961, 1979: 37-40; Fry, 1980; Fry, Schober and Björkqvist, 2010; Hinde, 1974:
269; Maynard Smith and Price, 1973; Riechert, 1998; Schaller, 1972: 55).
Most of this restrained intraspecific aggression in the animal kingdom
occurs between males who are competing directly or indirectly for mates
(Fry et al, 2010). For example, male mule deer “fight furiously but harm-
lessly by crashing or pushing antlers against antlers, while they refrain from
attacking when an opponent turns away, exposing the unprotected side of
its body” (Maynard Smith and Price, 1973: 15). It is in the survival interests
of both contestants to follow the rules of restrained, ritualized fighting so
that they minimize the risk of injury and reduce energy expenditure. This
point is illustrated by the fact that out of 1,314 sparring matches between
pairs of male caribou only six escalated fights were observed (Alcock 2005).
This is a ratio of one serious fight to every 218 ritualized contests.
Blanchard and Blanchard (1989: 104) explain: “In evolutionary
terms…successful individuals will be those with techniques which enable them
to avoid agonistic situations involving serious possibilities of defeat or injury,
while leaving them to continue in more promising situations.” The aggressive
behavior of a given species can then be seen as the outcome of natural selection
operating over many generations, refining behavioral patterns so as to maximize
fitness benefits and minimize fitness costs. This idea is summarized by Bernstein
(2008: 60): “The potential costs of fighting are such that natural selection has fa-
vored individuals that avoid taking risks when the cost to themselves is likely to
exceed the benefits of anything obtained by engaging in that interaction.”
Noncontact agonistic displays, ritualized competitions (as opposed to se-
rious fighting), and submission signals used to end a fight prior to serious in-
jury are widespread among animals because over evolutionary time, such be-
haviors have conveyed fitness benefits on those individuals who have prac-
ticed them over those who did not (Archer and Huntingford, 1994: 3-4;
Aureli and de Waal, 2000; Fry, 1980; Fry et al., 2010; Hinde, 1974: 270, 272;
Maynard Smith and Price, 1973). Generally speaking, the evolutionary “logic
of animal conflict,” as Maynard Smith and Price (1973) title their classic paper,
means that natural selection as a recurring pattern rewards the limited use of
force over “no holds barred” fighting. The widespread appearance in species
after species of restrained aggression between conspecific rivals instead of le-
thal tactics provides an important contextualizing precedent against which to
formulate hypotheses about human aggression. Based on numerous studies of
Neurobiological and Evolutionary Perspectives on Nonkilling 41
animal aggression, the logical hypothesis would be that humans also have
evolved restraint against killing, not a predilection for it.
Aversion to Killing: Military Science and Nomadic Forager Studies
A wealth of knowledge has been accumulated in military science and
thoroughly reviewed by Grossman (1995) and Grossman and Siddle (2008)
that supports the conclusion that humans have an aversion to killing. The
resistance of soldiers to kill other human beings has been documented
across diverse wars and societies from U.S. troops in World War II, French
officers in the 1860s, Argentine soldiers during the Falkland Islands War, the
battle of Gettysburg during the American Civil War, and more generally
throughout history (Grossman and Siddle, 2008: 1802).
One of the most intriguing examples of the unwillingness on the part of
soldiers in combat to actually fire at their fellow human beings comes from an
analysis of 27,574 muskets recovered from the Civil War battlefield at Get-
tysburg, Pennsylvania. Nearly 90 percent of the muskets were loaded. Addi-
tionally, about 12,000 (44 percent) of the weapons were loaded more than
once with some 6,000 having between three-to-ten rounds packed into the
unfired gun barrel. Grossman (1995) points out that if soldiers were desper-
ately firing their weapons as soon as they had loaded them, only some five
percent of the guns, not nearly 90 percent, would have been loaded, and cer-
tainly not loaded two or more times. Clearly, a huge number of soldiers un-
der close range combat at Gettysburg were spending their time loading and
reloading their guns rather than firing them to kill enemy soldiers.
A classic study of weapon firing rates was conducted during World War
II by U.S. Army historian Brigadier General S. L. A. Marshall. After conduct-
ing extensive post-combat interviews with soldiers, Marshall concluded that
only 15-to-20 percent of the men fired their weapons at a human target
(Grossman and Siddle, 2008: 1802). Others fired without aiming, or into
the air, or did not fire at all. The phenomenon is also reflected in statistics
on aerial “dog fights” of World War II: Less than one percent of U.S. fighter
pilots accounted for 30-to-40 percent of the enemy aircraft shot-down in
the air whereas the majority of combat pilots did not shoot down a single
enemy plane, and many never even tried to do so (Grossman, 1995). Gen-
eral Marshall wrote that “the average and healthy individual…has such an
inner and usually unrealized resistance towards killing a fellow man that he
will not of his own volition take a life if it is possible to turn away from that
responsibility” (Marshall quoted in Grossman, 1995: 29).
42 Nonkilling Psychology
This resistance towards killing is reflected in the greater amount of psychi-
atric symptoms in the soldiers who were involved in killing in comparison with
military personal who were not expected to kill but who still faced high risks of
being killed, such as medical personnel or soldiers on reconnaissance missions
behind enemy lines (Grossman and Siddle, 2008). In light of the “problem” of
getting men to kill, it is not surprising that combat training has been re-
designed since World War II to overcome the inhibitions towards killing on the
part of typical soldiers that cause them “to posture, submit, or flee, rather than
fight” (Grossman, 1995: 28). Another argument in favor of the human resis-
tance towards killing are high rates of depression, PTSD, suicide, domestic vio-
lence, and a host of other problems faced by war veterans which show that
participation in killing is psychologically very costly and traumatic. Only one-to-
two percent of the men in combat lack the typical inhibitions toward killing,
and they exhibit sociopathic tendencies (Grossman and Siddle, 2008).
Turning to data from nomadic forager societies, Fry et al. (2010) have
suggested that at least three kinds of natural selection pressures have favored
nonkilling over killing in humans. First, in the previous section, nonlethal, ag-
gression is the rule, not the exception, in the animal kingdom. This observa-
tion is important because it reflects numerous naturalistic experiments during
evolutionary history that have resulted in the same outcome time and again:
Attempting to kill conspecifics is rarely favored by natural selection. This cor-
pus of evidence provides an important precedent for proposing that evolu-
tionary selection pressures have favored restrained forms of aggression over
lethal patterns in humans also. Given the amount of violence in today’s world,
this argument may seem to be counterintuitive. However, today’s world is
dramatically different from the conditions under which the human species has
evolved and if we are discussing proclivities for killing as part of an evolved
human nature, we must focus attention on environment of evolutionary
adaptedness and the selection pressures that have operated on humankind.
A second selection force favoring nonlethality in humans as well as in
other animals involves inclusive fitness. The concept of inclusive fitness
holds that since relatives have alleles in common, then selection should fa-
vor the good treatment of one’s relatives (Fry et al., 2010; Fry, 1980, 2006).
In extant foraging band societies, a huge amount of daily social interaction
takes place among genetic relatives and this was almost certainly the case in
the ancestral past as well. Killing and injuring relatives has a negative effect
on inclusive fitness and therefore should have been selected against.
The third possible selection pressure against killing involves the observed
tendency for the close family members of a homicide victim in nomadic fora-
Neurobiological and Evolutionary Perspectives on Nonkilling 43
ger societies to avenge the death of their relative by killing the killer (Fry et
al., 2010). Thus, by committing a homicide, a killer often signs his own death
warrant and consequently lowers his own fitness. Revenge was found to be
the most common motive for committing homicide among the sample of 21
nomadic forager societies in an ethnographic database called the Standard
Cross-Cultural Sample (Fry, in press a, in press b). The typical pattern is that,
motivated by feelings of revenge, a homicide victim’s family may attempt to
kill the killer. If they succeed, this payback killing typically ends the matter be-
cause the two killings cancel each other (Fry, 2006: 230). This tendency is il-
lustrated by the Micmac belief that “If thou killest, thou shalt be killed” (Le
Clercq, 1910: 286), as well as in the observation for the Chukchee of Siberia
that “a murder rarely remains unavenged” (Bogoras, 1975: 663). This re-
venge pattern also is apparent among the Montagnais-Naskapi of Canada’s
Labrador Peninsula (Lips, 1947: 470), the Ingalik of western Canada (Osgood,
1958, p. 54), and the Yukaghir of Siberia. (Jochelson, 1926), the Ju/’hoansi of
the African Kalahari Desert (Lee, 1979: 391), and other nomadic forager so-
cieties. Given that the nomadic band social organization is the social type un-
der which humans evolved, the fitness ramifications favoring nonkilling may
have been significant (Fry, 2006, in press a, in press b).
To sum-up, computer simulations, data on animal behavior, evidence for
an aversion for killing from military sciences, and the insights we can glean by
analogy from an examination of extant nomadic forager societies converge to
suggest that natural selection has not favored killing over the course of human
evolution. In fact, these diverse bodies of knowledge converge to suggest an
alternative hypothesis: Killers probably have been selected against in the ances-
tral evolutionary environment due to the same types of cost-benefit selection
forces that have acted against escalated aggression in other species, due to
humans having evolved in small groups consisting largely of relatives, and due
to the tendency in nomadic band society for the family of a homicide victim to
attempt to kill the killer in revenge for the loss of their loved-one.
A Psycho-Social Model Explains More than an Evolutionary
Psychology “We-Are-Evolved-Killers” Proposition
If the goal is to understand killing and nonkilling, then we must begin by not-
ing the variation in these behaviors across time and space. First, not all societies
engage in war (Fry, 2006). The existence of countries that have successfully
avoided wars for long periods of time such as Costa Rica, Sweden, Switzerland,
and Iceland offer a challenge to the idea that humans have an evolved predilec-
44 Nonkilling Psychology
tion for killing. Second, although homicide rates vary tremendously from one
society to the next and also change over time within the same society, the vast
majority of people never kill or attempt to kill anyone. It is difficult to see how
the proposition that natural selection has favored males that kill over those who
do not explains this inter-societal and intra-societal variation in killing and the
fact that most humans do not ever kill. On the other hand, a number of proxi-
mate psychological, social, and economic factors offer more promising explana-
tions of these phenomena (Nisbett and Cohen, 1996). We will illustrate this
point by focusing on the importance of values in affecting behavior.
Values are conscious, trans-situational expressions of basic human needs
which serve as guiding principles in a person or a social entity (Schwartz,
1992, 1994). Schwartz proposes an integrated system that is structured by
ten value types (
Hedonism, Stimulation, Self-Direction, Universalism, Benevo-
lence, Tradition, Conformity, Security, Power
, and
Achievement
), each char-
acterized by its own motivational goal. According to Schwartz (1992) the
value system is organized by two dimensions: a Self-Transcendence vs. Self-
Enhancement dimension and an openness to change vs. conservatism dimen-
sion. These two dimensions underlie motivations: The value types Universal-
ism and Benevolence both involve concern for others whereas Achievement
and Power both emphasize concern for the self; Self-Direction and Stimula-
tion involve openness to change whereas Tradition, Conformity, and Security
emphasize resistance to change (Schwartz, 1992, 1994).
Conceptualization of values as goals to aspire to implies that values can
motivate individuals to behave in certain ways by guiding their judgment re-
garding which actions are considered as more justified or more desirable
than alternatives (Ajzen, 2001; Ball-Rokeach and Loges, 1996; Feather,
1992, 1995; Schwartz, 1994; Verplanken and Holland, 2002). Values are
connected to selfhood (Smith, 1991; Feather, 1992), constitute a core of
one’s personal identity (Bilsky and Schwartz, 1994; Hitlin, 2003), and hence
can be viewed as distal determinants of attitudes and decisions (Hitlin,
2003;
Hitlin and Piliavin, 2004; Lönnqvist, Leikas, Paunonen, Nissinen and
Verkasalo, 2006; Rohan, 2000; Verplanken and Holland, 2002).
A consideration of cultural beliefs, attitudes, norms, and values is crucial
for understanding why certain social groups favor nonviolent methods of
resolving conflicts whereas other societies are more open to the use of vio-
lence (Bonta and Fry, 2006; Fry, 2009; Miklikowska and Fry, 2010). Re-
search shows that value priorities constitute a motivational context within
which violence and warfare are perceived as either legitimate or illegiti-
mate. According to Basabe and Valencia (2007) and UNESCO (1995), the
Neurobiological and Evolutionary Perspectives on Nonkilling 45
structural bases for a culture of peace are related to values of egalitarianism,
harmony, and tolerance within a society all of which correspond with the
Self-Transcendence dimension of basic human values (Schwartz, 1994).
Consequently, the values constituting the Self-Transcendence dimension
have been found to be antithetical to violence, whereas the values from the
Self-Enhancement dimension correlate with aggressive ways of behaving.
Specifically, values representing the Self-Transcendence dimension have been
found to be positively linked with cooperative behaviors (Sagiv, Sverdlik and
Schwartz, 2010), altruistic behaviors (Bardi and Schwartz, 2003; Lönnqvist et
al., 2006; Omoto and Snyder, 1995), internal and external peacefulness of
groups (Miklikowska and Fry, 2010) as well as with prosocial views such as
positive perceptions towards immigration, support for an inclusive moral uni-
verse (Schwartz, 2007), “macro worry”
(a concern about the state of the
world and society) (Schwartz, Sagiv and Boehnke, 2000), and readiness for
contact with members of an out-group (Sagiv & Schwartz, 1995; Biernat,
Vescio, Theno and Crandall, 1996). Consequently, Self-Transcendence values
correlate negatively with violent behavior and bullying (Knafo, 2003; Knafo,
Daniel and Khoury-Kassabri, 2008), authoritarianism (Altemeyer, 1998;
Cohrs, Moschner, Maes and Kielmann, 2005a), attitudes favoring war (Cohrs,
Moschner, Maes and Kielmann, 2005b), noninclusive moral universe
(Schwartz, 2007), and social dominance orientation (Cohrs at al., 2005b). On
the other hand, values congruent with the Self-Enhancement value dimension
are negatively related to the expression of empathy for others, altruism, and
cooperation (Bardi and Schwartz, 2003; Myyry and Helkama, 2001; Sagiv et
al., 2010), and positively related to violent behavior and bullying (Knafo,
2003; Knafo et al., 2008), authoritarianism (Cohrs et al., 2005a),
and “micro
worry” (concern for one’s self) (Schwartz et al., 2000).
Clearly human beings have a potential for competition, aggression, and
killing (Fry, 2004, 2006). Yet, whether this potential becomes an enacted real-
ity depends on the specific cultural setting (Howell and Willis, 1989). Close
observation of peaceful and nonwarring societies draws attention to the role
of values in maintaining social tranquility (Bonta and Fry, 2006; Dentan, 1978;
Fry, 2009; Huesmann, 1988; Miklikowska and Fry, 2010). Cultural settings
wherein Self-Transcendence values dominate seem to pattern social behavior
in a peaceful way (Staub, 1996). To illustrate this, we will consider briefly the
Semai of Malaysia, the Paliyan of India, and the Ifaluk of the Pacific.
Semai daily life is characterized by nonviolence. The Semai neither war nor
feud. They rarely use any form of aggression to deal with conflict and, in fact,
“usually tolerate annoyances and sacrifice personal interests rather than precipi-
46 Nonkilling Psychology
tate an open confrontation”
(Robarchek, 1997: 54). Spousal quarrels rarely oc-
cur, children are not corporally punished, neighbors seldom argue, even fighting
among children is a rarity, and homicides are virtually nonexistent (Robarchek,
1977; Robarchek and Dentan, 1987; Robarchek and Robarchek, 1992). Even
when faced with slave-raiding, “the Semai response was always a disorganized
and headlong flight into the forest” (Gregor and Robarchek, 1996; 161).
Two paramount Semai values are affiliation (harmonious interpersonal
relationships within the band, agreeing, not fighting, not getting angry, not
causing trouble) and nurturance (giving both emotional and material sup-
port to others, helping, cherishing, feeding) (Robarchek, 1979, 1980). The
importance of affiliation and nurturance leads naturally to consideration for
the needs of other people--to Self-Transcendence values. The Semai hold
an ideal image of their social group as benevolent and
nurturing, “we are all
siblings here, we take care of one another,” and “when I couldn’t hunt, you
took care of me; when you were sick, I took care of you” (Robarchek,
1989b: 911). The importance of affiliation is also a direct reason for the Se-
mai tremendous fear of conflict (Robarchek, 1980).
Adopting a social learning perspective, it can readily be seen that raising
children in an environment that emphasizes the cultural values of nurturance
and affiliation means that the youngest members of Semai society have few
opportunities to learn physical aggression (Moss, 1997). In the Semai nonvio-
lent social setting, the learning though observation and imitation of aggression
is nearly impossible. As Dentan (1978: 132) remarks, “even if a child wanted
to become violent, it would have no very clear idea of how to proceed.”
In summary, the values of affiliation, nurturance, tolerance, egalitarian-
ism, peace, and conflict avoidance (representing the Self-Transcendence
value dimension) provide a foundation for nonviolent Semai behavior.
Physical aggression is incompatible with Semai values and the image they
hold of themselves (Robarchek, 1979).
The Paliyan place great value on equality, respect, and nonviolence.
They believe that “everyone merits equal respect by virtue of being a hu-
man being” (Gardner, 2000b: 85). To Paliyan thinking, if a person interferes
with the freedom of another, then he or she is acting disrespectfully. This
set of values is incompatible with using aggression as a means of dealing
with conflicts. For the most part, the Paliyan use effective nonviolent tech-
niques such as third party conciliation, avoidance of conflict situations, and
self-restraint, as reflected in the nonviolent ethos, “If one strikes, the struck
man keeps still. It is our main motto” (Gardner, 1999: 263),
Neurobiological and Evolutionary Perspectives on Nonkilling 47
Gardner (2000a: 225) recorded a mere 20 examples of
disrespect
over
a four-and-a-half month period in one Paliyan band. Most instances of disre-
spect were very mild, for instance, when adults lightly slapped youngsters,
or when a person with bruised feelings got up and left in complete silence.
Even the most serious instances of disrespect, generally those involving
marital jealousy, were very mild if viewed from a culturally comparative
perspective. The vast majority involved no physical contact at all, and some-
times no words were exchanged, as when a person simply left the band
(Gardner, 1972: 439). Gardner (1999) failed to uncover any cases of homi-
cide. The Paliyan do not engage in feuds or war and respond to threats of
violence from outsiders by moving away (2004, 2010).
The nonviolent, nonwarring Semai and Paliyan provide a poignant illus-
tration of the human capacity for living in peace and at the same time raise
questions against the notion that killing has been selected over evolutionary
time to become a natural attribute of humanity. The Ifaluk of Micronesia is
another society that contradicts the idea that human nature includes an
evolutionary predilection to kill other people. The Ifaluk have been studied
by Burrows (1952) and Spiro (1952) following WWII and by Lutz (1988)
some 30 years later. The lack of physical aggression on Ifaluk caught the at-
tention of all three anthropologists. Burrows (1952: 25) writes:
What is striking about Ifaluk…is the fact that there is no discrepancy be-
tween its cultural values (the ideal culture) and its actual behavioral pat-
terns (the real culture). Not one individual could remember a single case
of murder, rape, robbery, or fighting; nor did the ethnographer witness
such behavior in his seven-month study. It was almost impossible to con-
vey to the people the concept of murder, the thought of wantonly killing
another person is so completely alien to their thinking.
In a cross-cultural study of rape, Minturn and her colleagues (1969) rated
Ifaluk as a society where rape does not take place.
Lutz (1988: 199) explains
that in the view of the people of Ifaluk, violence was almost inconceivable:
“The horror that the idea of violence evokes for the Ifaluk was evident in
their discussions of the rumored aggressive tendencies of Americans and
some other groups. Several people checked with me to see if the stories they
had heard about the existence of murder in the United States were in fact
true.” This represents an interesting turn-around to some theorists who have
trouble imagining that war and violence are not manifested in every human
society (e.g., Wrangham and Peterson, 1996). Lutz (1988) also recounts that
when the people of Ifaluk watched American movies that the U.S. Navy
48 Nonkilling Psychology
brought to the atoll and saw the characters in the films being shot and beaten
they were terrified and sickened for days. The case of Ifaluk runs counter to
assumptions that humans have evolved predilections towards killing,
The Ifaluk—like the Semai, Paliyans, and many other peaceful peoples
around the world—have a Self-Transcendence value orientation that inhibits
physical aggression. Anthropological research shows that Self-Transcendence
values may contribute to peace in three ways: by directly discouraging violent
behavior; by favoring nonviolent responses to conflicts such as discussion,
avoidance, and tolerance; and by encouraging self-control and restraint
(Baszarkiewicz and Fry, 2008; Gardner, 2010; Miklikowska and Fry, 2010).
Although it is possible that the simple forms of social organization provide
more certain conditions for the translation of values into practice the com-
parisons of communities that differ in terms of values but are close geographi-
cally illustrate the power of values in contributing to differences in violence
(Bonta, 1996; Fry, 1994, 2004, 2006, 2007; Fry and Fry 1997; O’Nell, 1989;
Robarchek and Robarchek, 1992; Staub, 1996).
Methodological Problems with the Yanomamö
Unokai
Study
Ferguson (1989) wrote a commentary on Chagnon’s (1988) findings and
raised the question whether
unokais
and non-
unokais
were really of com-
parable ages, suggesting instead that some of the difference in reproductive
success between the two groups actually was related to age differences be-
tween the groups. Chagnon (1989) simply ignored Ferguson’s age question
and in subsequent publications continued to state that
unokais
had over
three times the number of offspring as non-
unokais
of the same age
(Chagnon 1990: 95; Chagnon 1992a: 205; Chagnon 1992b: 239-240;
Chagnon, 2010). Years later, Chagnon continues to sidestep the age issue as
evidenced by his unwillingness to provide the actual means and standard de-
viations for the ages of the
unokais
and the non-
unokais
(see the Appendix).
However, some simple mathematics applied to the Chagnon’s published data
shows unequivocally that the majority of the
unokais
are over 41-years of age,
whereas the majority of non-
unokais
are 30-years of age or younger. Fry
(2006) estimates the age difference between the two groups of men to be at
least 10.4 years. Obviously, the age distributions are very different for these
two groups of men and therefore, before any claim can be made that one
group averages more than three times as many offspring as the other
group, this substantial age difference must be taken into consideration.
Neurobiological and Evolutionary Perspectives on Nonkilling 49
A second complication that makes the interpretation of Chagnon’s
(1988)
unokai
finding problematic is that headmen generally tend to have
more wives and children than other men (Ferguson, 1989; see also
Chagnon, Flinn and Melancon, 1979: 318). Using data published by
Chagnon, Fry (2006) presents calculations that correct simultaneously for
the effects of headmanship and age. The results show that if any
unokai
re-
productive advantage exists at all, then such an advantage is nowhere near
the three-fold figure that has proliferated in the literature.
There are two more issues worth mentioning. First, Chagnon (1988) in-
cluded in his study only Yanomamö men that were alive at the time of his re-
search. Ferguson (1989) points out that this procedure could bias the results
because the ethnographic data on the Yanomamö suggest that
unokais
are at
greater risk of being targeted in revenge-killings than are non-
unokais
(see also
Lizot, 1994: 855). Chagnon’s inclusion of solely men that were alive at the time
of his study is questionable because it implicitly presumes that
unokais
and
non-
unokais
have an equal chance of being killed, whereas ethnographic data
suggest that killers have a higher chance of meeting a violent end than do
nonkillers. Chagnon (1988: 986, emphasis added) explains that “Raiders may
inflict deaths on their enemies, but by so doing
make themselves and kin prime
targets for retaliation
.” Second, Chagnon (1988) conflates the Yanomamö cul-
tural concept of
unokai
with actual, physical killers (Albert, 1989). Chagnon
(1988) takes an entire population of living men and classifies them dichoto-
mously as either
unokais
or non-
unokais
. A person can undergo the purifica-
tion ceremony, however, for various reasons: A man may directly, physically
kill another man; A man may go along on a raid and, take part in shooting a
volley of arrows blindly into a village, perhaps killing someone in the process; A
man may shoot an arrow into a corpse; A man may kill someone through sor-
cery, shamanism, or by destroying the victim’s animal alter ego (Albert, 1989).
Thus the Yanomamö undergo the purification ceremony for multiple reasons
and there are multiple paths to attaining the label of
unokai
. Chagnon (1988),
however, explains that all the so-called
unokais
in his sample directly, physically
participated in killing. If that is the case, what happened to the other types of
unokais
in Chagnon’s dichotomous classification? Since no men are left out of
the comparison, then either some men who are
unokais
in the eyes of the
Yanomamö (for killing via supernatural means, for example) are included in
Chagnon’s non-
unokai
group, or else Chagnon’s
unokai
group in fact includes
some men who have undergone the purification ritual for “killing” corpses,
practicing sorcery, and so on, but have not actually, physically killed anyone.
Finally, it is problematic to gloss
unokai
as warrior, as many writers have done,
50 Nonkilling Psychology
because some men have undergone the purification ceremony after commit-
ting homicide within their own village (Chagnon, 1988).
In conclusion, there are multiple reasons for doubting that
unokais
have
any real reproductive advantage over non-
unokais
at all. If any such advantage
does exist, it clearly is only a fraction of the amount reported by Chagnon.
The
unokais
as a group are substantially older than the non-
unokais
. “Even
the most conservative calculation (age alone) cuts the originally reported
unokai
advantage by 56 percent, whereas the most liberal (yet plausible) cal-
culation combining corrections for age and headman effects totally eliminates
any
unokai
advantage” (Fry, 2006: 198). But correcting for age and headman
effects does not fix all the problems. Comparing samples of living men is
problematic because it obscures an almost certain higher mortality rate for
unokais
than for non-
unokais
. Finally, although the term
unokai
is an indige-
nous concept that results from multiple types of killing, Chagnon (1988) con-
flates its meaning with a Western focus on physical killing. These various
methodological and analytical issues are cumulative and obviously far from
trivial. In light of these multiple concerns, any assertion that
unokais
have
more offspring and wives than non-
unokais
is problematic.
Two Other Studies Show the Opposite of the Yanomamö Study
Using the findings from one study to generalize to “all social groups on
Earth” (Ghiglieri, 1999: 194) is scientifically unsupportable. And making such
a generalization is even more problematic when other studies show the
opposite. Moore (1990) examined ethnohistorical and census data for the
warlike Cheyenne and discovered that Cheyenne war chiefs had
lower
re-
productive success and shorter lives than did Cheyenne peace chiefs.
The Waorani of Ecuador had a very high rate of killing before foreign mis-
sionaries assisted the Waorani in making peace with each other (Beckerman
et al., 2009; Robarchek and Robarchek, 1998). Beckerman and colleagues
(2009) interviewed and gathered genealogical data for over 100 Waorani eld-
ers of both sexes to investigate possible relationships between participation in
lethal raiding and reproductive success. Beckerman et al. (2009) explain: “To
avoid some of the methodological objections raised to Chagnon’s work, we
included in our sample of warriors both living and dead men; we ranked their
aggression by the number of raids they participated in and not by a local term
of contested meaning with which they are labeled. Our analysis is free of the
problem caused by the inherent correlation of the warrior’s age with both
participation in raids and reproductive success.” The research team analyzed
Neurobiological and Evolutionary Perspectives on Nonkilling 51
whether the amount of raiding was associated with the survivorship of the
raiders, survivorship of their wives, number of wives, number of children
born, and survivorship of offspring to the age of 15 years, in other words, “life
history features presumably linked to individual fitness” (Beckerman et al.,
2009). They operationally defined
zealous warriors
in three ways: As those
Waorani men whose lifetime rate of raiding exceeded the average for all men,
exceeded the average for all men plus 0.5 standard deviations, and exceeded
the average for all men plus 1.0 standard deviation.
The key finding was that the zealous warriors had lower, not higher, life-
time reproductive success. Beckerman et al. (2009) conclude that: “More ag-
gressive men (i.e., zealous warriors) no matter how defined, do not acquire
more wives than milder men, nor do they have more children, nor do their
wives and children survive longer. In fact, the most statistically significant dif-
ference revealed by our analysis is in the other direction: Bellicose men have
fewer children who survive to reproductive age, a finding that strongly sug-
gests that they have lower individual fitness than less aggressive males.”
Finally, Beckerman and his colleagues point out that since their repro-
ductive success findings for the Waorani are the opposite of the findings re-
ported by Chagnon (1988), clearly the Yanomamö findings do not apply to
tribal societies in general. In our opinion, because the Waorani study in con-
trast to the Yanomamö study controlled for the spurious effects of age,
considered the reproductive life histories of both living and dead men, and
did not attempt to use cultural labels (i.e.,
unokai
) but instead counted ac-
tual numbers of raids undertaken, the Waorani results carry much more
weight than do the Yanomamö findings.
An evolutionary model of human killing/nonkilling should be consistent
with an accumulated knowledge base, not merely the results of one particu-
lar study. Especially because findings on two other societies, the Cheyenne
and Waorani, show the opposite, any claims that Chagnon’s (1988) findings
are pivotal to understanding the evolution or human aggression overstep
the bounds of reasonable scientific inference.
Conclusions
History has its quirks. Sometimes a single event has enormous conse-
quences, setting in place a cascade of subsequent developments. As the
young discipline of evolutionary psychology has evolved over the last two-
to-three decades, Chagnon’s (1988) report that killers-have-more-kids has
taken a central place in the evolutionary psychology hall of fame having had
52 Nonkilling Psychology
a tremendous impact on publications within evolutionary psychology that
deal with homicide, violence, and warfare.
Evidence for the substantial impact of this one article is twofold. First, the
finding that killers have more wives and children has been widely broadcast
across academic disciplines including psychology, economics, anthropology,
primatology, political science, biology, and medicine, as well as in the popular
press (e.g., Allman, 1988; Barash, 2001: 165-174; Burnham and Phelan, 2000:
88; Buss, 1999: 304-305, 2005: 210; Campbell, 1999: 212; Cronk, 1999: 80;
Daly and Wilson, 1994: 274; Gat, 2000b: 75, 76, 87 note 4, 2006: 58; Geary,
1998: 317-318; Ghiglieri, 1999: 144, 193-194; Konner, 2006: 5; Low, 1993:
21, 26, 31; Manson and Wrangham, 1991: 369, 374; McCarthy, 1994: 107;
Pinker 1997: 510, 2002: 116; Potts and Hayden, 2008: 162; Symons, 1990:
436-437; Thayer, 2004: 131; Wrangham and Peterson, 1996: 64-74). Second,
many discussions of warfare from an evolutionary perspective uncritically re-
count the finding and then advance variations of the interpretation that killing
probably paid fitness dividends over the evolutionary history of the human
species (e.g., Buss 2005; Gat, 2006; Konner, 2006; Pinker, 1997, 2002; Thayer,
2004; Wrangham and Peterson, 1996). For example, Potts and Hayden (2008:
162, 164, emphasis in original) follow-up a retelling of the
unokai
findings with
the statement: “The Yanomamö…are not only like us—they
are
us.”
It is pretty unusual in science for findings from a problematic study to be
reiterated uncritically across many fields. Playing up one sole finding as reveal-
ing larger evolutionary truths about human nature and a propensity for killing
is not exactly good science. To be taken seriously, evolutionary explanations
of killing and human nature should be grounded in evolutionary theory, con-
struct realistic models that can generate testable hypotheses, and rest on
solid bodies of data. A series of methodological and analytical issues render
Chagnon’s (1988) killers-have-more-kids finding difficult to interpret. We
have noted how age, headmanship, exclusion of deceased men from the
sample, and ambiguous group membership issues combine to call the verac-
ity of the findings into question. Additional methodological concerns about
Chagnon’s (1988) findings also have been voiced by others (e.g., Albert,
1989; Lizot, 1994; Ferguson, 1989, 1995; Sponsel, 2010) but tend to be ig-
nored in favor of touting the original finding. The fact that the findings have
not been replicated by studies on the Waorani and Cheyenne (Beckerman
et al., 2009; Moore, 1990) at the very least should discourage the type of
over-zealous generalizing that has been done on the basis of this one study.
We suggest that the idea that humans have evolved an inclination for
killing is actually 180 degrees off course and encounters various stumbling
Neurobiological and Evolutionary Perspectives on Nonkilling 53
blocks. For example, how are nonwarring, nonfeuding, and nonviolent so-
cieties such as the Semai, Paliyan, and Ifaluk to be explained? Why is the
supposed inclination toward killing not manifested in such cases? Buss’s
(2005) answer is that the inclination toward killing is triggered in particular
social situations and thus is not always and everywhere active. In the ab-
sence of convincing evidence that any such inclination to kill exists at all, we
suggest that a more parsimonious explanation is that the amount of killing in
a given society reflects proximate psycho-social influences, which result in
variable rates of killing within and across societies.
We presented multiple reasons why an interpretation exactly opposite to
the now famous killers-have-more-kids idea actually makes more evolutionary
sense. First, at the theoretical level, the evolutionary models and game theory
simulations of animal conflict indicate that limited aggression is a better fitness
enhancing strategy than escalated aggression. Second, data on animal competi-
tion across a great number of species suggest the natural selection tends to
disfavor lethal aggression against conspecifics under most circumstances. And
in correspondence with the corpus of animal studies, the findings on the
Waorani and the Cheyenne show that the men who killed the most had
lower
fitness that their compatriots (Beckerman et al., 2009; Moore, 1990). Third,
evidence from military science suggests that humans may well have a strong
inhibition against killing other humans. Interestingly, Chagnon (1988: 987) ex-
plains that “many raiding parties turn back”, that individual Yanomamö raiders
“drop out for reasons such as being ‘sick’ or ‘stepping on a thorn,” and that a
majority of the
unokais
have participated in a killing only once in a lifetime. Do
these facts suggest, ironically, a reluctance to kill on the part of the very
Yanomamö men whose bellicosity so many authors have touted? Fourth, an
examination of extant nomadic forager societies suggests that killing may well
have been selected against, not favored, in this type of social organization.
Three types of possible selection pressures against killing were discussed.
As an overall conclusion, bountiful theoretical and empirical reasons ex-
ist for making the prediction that killers will be found to average
less
off-
spring than nonkillers across a variety of social circumstances. This predic-
tion stems from an application of evolutionary theory and observations of
animal and human behavior. We suggest that this alternative prediction to
the killers-have-more-kids idea merits further examination.
54 Nonkilling Psychology
Acknowledgment
Some of the data reported in this chapter were collected during research
funded by the National Science Foundation (Grant number 03-13670), whose
financial support is gratefully acknowledged. Any opinions, findings, and conclu-
sions or recommendations expressed in this material are those of the author
and do not necessarily reflect the views of the National Science Foundation.
Appendix
This Appendix contains excerpts from an online discussion between Napo-
leon Chagnon and Douglas P. Fry regarding the
unokai
and non-
unokai
age is-
sue. This series of posts appeared on the Evolutionary Psychology list at ya-
hoogroups.com between March 30, 2008 and April 5, 2008. Additional parts of
this discussion are online.
1
The mathematical calculations and discussion re-
ferred to in this Appendix can be found in Fry (2006: 184-199, 288-305).
On March 30, 2008, Napoleon Chagnon posted
:
…Ultimately, what is really at issue behind much of the criticism of my
work are two nearly ‘sacred’ Anthropological Truths, given down from
above to the anthropological laity by self-appointed Ayatollahs like
Sahlins. The first one is that warfare is rare to nonexistent in the pristine
primitive world of hunters and gatherers because Original Man is basically a
nice critter, a Noble Savage. Many of my anthropological critics seem to be
upset to the point of suggesting that my data on Yanomamö warfare and
violence is ‘suspect,’ ‘exaggerated,’ ‘cooked,’ ‘controversial,’ etc. and might
my data might possibly cause people to question this Noble Savage view
because my empirical findings are plausible, meticulously documented and
have become widely known. …The second issue is the question of whether
or not anthropology is a “science” and whether or not it can be “scientific”
if the humans in human behavior can be “factored out.”
On April 1, 2008, Douglas P. Fry posted
:
…Most striking is the fact that Chagnon’s own data show that
unokais
as a
group are substantially older than non-
unokais
. Despite his claims that
unokais
and non-
unokais
are of comparable ages, mathematics show that they are not.
From carefully examining Chagnon’s own published data, it can be determined
that 55% of the
unokais
are over 41 years of age, whereas 56% of the non-
1
<http://naturalbornnonkillers.blogspot.com>.
Neurobiological and Evolutionary Perspectives on Nonkilling 55
unokais
are younger than age 31. I calculate, again using Chagnon’s own pub-
lished data, that the age differences between these two groups of men is at
least 10.4 years. Older Yanomamö men have more offspring than younger
Yanomamö men, whether or not they are
unokais
. Chagnon’s published data
show this clearly. What this means is that huge age differences between
unokais
and non-
unokais
throw the whole finding that ‘killers have more kids’ into seri-
ous doubt, because older men have more kids than younger men.
On April 1, 2008, Napoleon Chagnon posted
:
…I carefully read the lengthy endnote in Fry’s 2006 publication at about
the time it appeared and concluded that with some shaky but creative as-
sumptions about my age estimates for the Yanomamö males in my study—
both
unokai
and non-
unokai
—one could try to make the case Fry just
posted today on the Ev-Psych list.
…I have never published data that would enable someone to determine
who specifically was a ‘killer,’ his name, his village, his age, how many wives
he had, and how many offspring. In short, the data needed to make the
criticisms that Fry makes can not be gleaned from my published data.
On April 2, 2008, Douglas P. Fry posted
:
…Either the math is correct or not. I have explained in detail what I am
doing at every step, cite the sources of Chagnon’s data I am using, present
explicitly what assumptions I am making and why, and present all the calcu-
lations in black and white. Even more details are in the book, such as how
the demographic data published in one of Chagnon’s 1979 sources provide
the Yanomamö population age pyramid for use in my calculations.
…If Napoleon Chagnon thinks that my calculation of age interval averages
is wrong, well let’s not forget the obvious. He is the guy that holds the indi-
vidual age data for each man in this own sample. All Chagnon has to do is to
tell us readers the actual age averages for the
unokais
and non-
unokais
. He
collected this data, so if he thinks my estimates are “shaky,” then let’s hear
what the actual age figures are. We will then see how accurate my estimate is
of at least 10.4 years in age difference between the
unokais
and non-
unokais
.
At the same time we will also see if Chagnon is correct in his assertions that
the
unokais
and non-
unokais
are of comparable ages. We both can’t be right.
Instead of taking pot-shots at my estimates, why not come up with the actual
figures? We will then have actual numbers regarding the age differences be-
tween
unokais
and non-
unokais
for the first time.
56 Nonkilling Psychology
On April 3, 2008, Napoleon Chagnon posted
:
…A. Fry’s method for re-calculating ages from my data assumes that ages
are relatively evenly distributed within each of my four age groupings. This is
probably not true. The Yanomamö are illiterate and have no idea of their ages
in years and I have to estimate their ages by “on-site inspection”—looking them
over in person (and taking a photograph of them). Estimating ages is easier for
the youngest people but difficult for adults. Consequently when I first census a
village many people are estimated to be 20, 30, 40; a few are estimated be 25,
35, 45, etc. and none are estimated to be 22, 29, 33, etc. Also, some age esti-
mates of individuals might be off more than others—I might estimate someone
to be 25 when he might be in fact be 33—if that could be known.
…B. I have not claimed that
unokais
and non-
unokais
are of compara-
ble ages in general: I put them into four different age groups and said that
men within each of these groups were of comparable age. It is unlikely that
there are ‘huge’ age differences within these categories.
On April 3, 2008, Douglas P. Fry posted
:
…Chagnon has never published the actual average ages for the
unokais
(n
= 137) and the non-
unokais
(n = 243), but he has claimed repeatedly that
the
unokais
and non-
unokais
he compares are the same age (e.g., Chagnon,
1990: 95; Chagnon, 1992a: 205; Chagnon 1992b: 239-240; see Fry 2006:
289, note 11.) Mathematically, the
unokais
and the non-
unokais
cannot be the
same age when they have these extremely different age distributions.
Chagnon’s four age categories does not adequately control for age distribu-
tions that are really different from each other. In my previous posting, I in-
vited Napoleon Chagnon to share with us the actual average ages for the 137
unokais
and the 243 non-
unokais
. Presenting the means and standard devia-
tions for these two groups would help to clarify the situation. (By the way,
sharing the mean ages for these two groups of men does not compromise
confidentiality, an important ethical concern previously mentioned by
Chagnon, but not applicable to the publication of aggregate statistics such as
means and standard deviations for groups of men.)
On April 4, 2008, Douglas P. Fry posted
:
…I hope that Dr. Chagnon will be forthcoming with the actual mean ages
and standard deviations for the 137
unokais
and the 243 non-
unokais
in his
sample.
Neurobiological and Evolutionary Perspectives on Nonkilling 57
On April 5, 2008, Napoleon Chagnon posted
[Fry’s] somewhat glowing accounts of ethnographies on various hunt-
ers/gatherers that show how they reportedly manage to constrain and re-
strain violence is supplemented with lessons from animal species which do
the same. He ends with the hopeful suggestion that “This type of data pre-
sents us with a very different evolutionary model of aggression than does
the
unokais
model that focuses on killing as a path to reproductive success.”
I get the feeling that my 1988
Science
article MUST be repudiated in cul-
tural anthropology lest it remain a viable ‘model’ of aggression, which I did
not suggest it was, but a possibility that seems to bother Fry.
Unfortunately, this is my last post on this topic. I’m trying to finish a
book and I don’t have time to re-explain basic Yanomamö ethnography—
nor is this the forum in which to do it. I also do not want to be confused
with, as Mark Hubey put it in one of in his posting on 4/3, those anthro-
pologists who ‘....prefer doing fourth grade arithmetic and fighting for dec-
ades over a problem that can be solved by undergrads.’
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