[Paleopsych] Meme 050: Skeptic: David J. Buller: Sex, Jealousy & Violence
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Mon Nov 28 00:45:19 UTC 2005
Meme 050: Skeptic: David J. Buller: Sex, Jealousy & Violence
Frank Miele's response, "Evolutionary Psychology is Here to Stay,"
appended below, is very good. But what's extraordinary about this exchange
is that Buller, for all his reservations about specific conclusions of
evolutionary psychology is one himself, unlike Steven Jay Gould. It's just
that Buller is more inclined to see our Stone Age brains mediated and
moderated by specific learning in specific cultures.
Gould's exaggerated attacks on sociobiology stemmed from two 20th century
leftist preoccupations, central planning and egalitarianism. Central
planning is, of course, in the interests of central planners (professors
most especially), and they hate the idea that our biology limits what
these planners can achieve.
I will not say that Buller's, or even Gould's, criticisms are without
merit. The one I like the most is that sociobiological explanations are ad
hoc, circular, and unverifiable. A sociobiologist claims some
psychological factor in our makeup is due to its adaptiveness during
(where else?) the Era of Evolutionary Adaptiveness. He can't actually go
back to the Stone Age and see what was really adaptive there, so he just
presumes that it was in fact adaptive.
This kind of attack is good clean fun and should serve as a warning to us
all, which it has. But what counts is not whether sociobiology offers
perfect explanations but how well it stacks up against earlier,
non-biological social explanations. (We economists do look at
competition.) Just think about the concepts that are used to explain
events and historical developments in history and the social sciences.
"Peer pressure," does this have anything like an exact definition? Do
studies ever try to quantify it? Do the variables that do, if they do, get
used to measure it stack up against routine criticisms?
Ditto for utility in economics (economists do know the standard
objections), the Industrial "Revolution" in history, and so on through
every concept used. Religion, culture, society, are these defined? No they
are not. Religions are more like medical diagnoses (or what Wittgenstein
called "family resemblances."): if four of six criteria are present, then
you've got a religion, although no one criterion is essential. (By the
way, those who say there are no races, since anthropologists come up with
different counts, should give us a count of the number of cultures in the
world or stop using the concept.)
And so if you have four of six criteria for a certain disease, the
physician now *understands* what is the matter with you and gives you a
certain pill. And a candidate for a religion meets four of six criteria,
the scholar now *understands* what's afoot and then can say or predict a
lot more about this now-certified religion.
This is how our Stone Age minds work, by this *feeling* of supposed
understanding. How it could be otherwise, I do cannot imagine, not in a
world that is not neatly divided up into neat, discrete categories and not
the continuous mess we see, and certainly not in a world where our brains
are only so big and where extracting facts is costly and where making
theories out of the facts is costlier. (Overarching theme of mine: the
world partakes of both the discrete and the continuous.)
The moral is that sociobiology works just as well as fields that eschew
the biological and pretend a kind of Creationism, that evolutionary
processes have stopped and that men might as well have been created.
I said above that Gould attacked sociobiology, not only on 20th
century-leftist central planning grounds but on (later) 20th
century-leftist egalitarian grounds. Dangerously, sociobiology might just
wander into human differences! What's decidedly remarkable is what Buller
says of evolutionary psychology:
A second problem concerns the doctrine that our minds are adapted to
the Stone Age. First, this idea greatly underestimates the rate at
which natural and sexual selection can drive evolutionary change.
Recent studies have demonstrated that selection can overhaul a
species' adaptations in as few as eighteen generations (for humans,
roughly 450 years).
This leaves wide open the possibility of racial differences in
intelligence!^ Indeed, evolutionary psychology is a field that split off
from sociobiology precisely for its inegalitarian possibilities and
studiously avoids studying anything that smacks of individual differences,
with the lone exception of sex.
[^Old timers will remember when "Ashley Montagu" would insist that human
races could not be more than 35,000 years old and that *therefore* racial
differences in intelligence could not have emerged, contradicting the
"racist" Carleton Coon, who claimed a period ten times as long. The good
(AntiRacist) guys were the "young earth creationists." Similarly, the
conservative Fundamentalists insist on early dates for the books of the
New Testament as we know them and that *therefore* there was not enough
time for them to have been tampered with by early Christians. The less
literalist liberals say the Gospels as we have them came late, after much
tampering to carry them away from the plain message of Jesus (which just
happens to be what liberals want to hear). Neither side has any idea how
long it takes to alter sacred documents! And my friend at the Nuclear
Regulatory Commission has no idea how likely a nuclear accident is and,
therefore, whether safety standards are not much to high already: he's
just a good liberal wanted to crack down on corporate greed. He honestly
admitted this charge! As far as the NT goes, I was much impressed that
J.A.T. Robinson, a liberal, would argue in _Redating the New Testament_
(1976) that all the NT books, in draft at least, antedate the destruction
of the Jewish Temple in 70 AD. Update to 2000 and the publication of
Dennis R. MacDonald (Claremont School of Theology), 1946- , _The Homeric
Epics and the Gospel of Mark_ (New Haven: Yale University Press) and I'm
convinced that there probably was little or no tampering, early or late,
but that this Gospel is a deliberate literary creation out of a collection
of sayings of the actual Jesus railing against the hypocrisy of his day
and merged to be compatible with resurrection account that appeared the
suppression of competition (killing by the Roman government) at the urging
of rent-seekers (Jewish religious establishment). Mark used Old Testament
prophecies and added lots of details about Jesus' life by way of numerous
dense and sequential parallels with the Homeric epics, all altered to hint
to the reader that Jesus is superior to Odysseus. It's the documentation
of the parallels, a typical literary form at the time called mimesis, that
is MacDonald's contribution. And so the best argument in my mind for
Christianity (as opposed to arguments for God in general), namely the
uncanny unity of the Bible, has been resolved to my satisfaction.]
The expected attacks on 20th century-leftist egalitarian grounds
are quite absent in Buller's article. This backs up my thesis that
egalitarianism, as the 21st century rolls on, is becoming less and less
the major preoccupation of politics. I'd have to reread Buller to horn it
into my idea that pluralism is becoming the major preoccupation of
politics in the current century, but I'm not going to stretch my thesis.
Just quite possibly, Buller's article, refreshingly, is just about the
scientific merits and demerits of evolutionary psychology and that
politics drives his thinking very little, compared to Steven Jay Gould.
P.S. Could someone give me a good précis about the modularity debates? It
makes no evolutionary sense to have hundreds or thousands of these
modules, as Buller claimed. And there's nothing incompatible with these
separate modules and submodules and an overall brain efficiency, which in
intelligence is called *g*. When getting Jensen to autograph a copy of
the 1969 Winter issue of the _Ha'va'd Educational Review_ at an AAAS
meeting on 1991.2.17, I asked him if his notions were incompatible with
those of Howard Gardner. He said no, and I asked him if his idea was that
intelligence is quick wit at the neuronal level, and he said that was a
David J. Buller: Sex, Jealousy & Violence
(from Skeptic magazine Vol. 12, No 1)
This quarter, Skeptic.com presents an article excerpted from Adapting
Minds: Evolutionary Psychology and the Persistent Quest for Human
Nature, by David J. Buller.
A Skeptical Look at Evolutionary Psychology
In nearly every newspaper or magazine these days you can find
evolutionary explanations for a variety of human behaviors -- for what
we seek in mates, why we are sometimes unfaithful, why we love our
children (but not our stepchildren), why men and women differ, and
even why husbands kill their wives. All of these explanations are
offered in the name of evolutionary psychology. But what is
There are actually two different answers to this question, and it is
useful to clearly distinguish them. On the one hand, many behavioral
scientists define evolutionary psychology simply as "the evolutionary
study of mind and behavior."1 So conceived, evolutionary psychology is
a field of inquiry, akin to mechanics, which is defined not by any
specific theories about human psychology, but by the questions it
investigates. And these questions cover a broad spectrum. Why do males
in some hunter-gatherer populations hunt, which offers highly variable
caloric returns, when they could reliably provide their families with
equivalent calories by gathering? Why do women in some hunter-gatherer
populations wait an average of four years between pregnancies? What
evolutionary forces drove cortical expansion in humans? How and why
did altruism, or language, evolve?
On the other hand, several prominent and influential behavioral
scientists -- led on the popular front by Steven Pinker (The Blank
Slate) and David Buss (The Evolution of Desire and The Murderer Next
Door) and on the academic front by Leda Cosmides and John Tooby (The
Adapted Mind) -- define evolutionary psychology as a specific set of
doctrines concerning the evolutionary history and current nature of
the human mind. In this sense, evolutionary psychology as a field of
inquiry has been elevated by its practitioners to an all encompassing
paradigm of Evolutionary Psychology (EP).
A defining doctrine of EP is that the human mind is massively modular,
containing "hundreds or thousands" of "special-purpose minicomputers"
called "modules," each of which evolved during the Pleistocene to
solve a problem of survival or reproduction faced by our
hunter-gatherer ancestors.2 Endowed with substantial innate knowledge,
yet a very narrow range of expertise, each module is dedicated
exclusively to solving a single problem -- for example, detecting
cheaters in social exchanges. A second defining doctrine of EP is that
our minds remain adapted to a Pleistocene hunter-gatherer lifestyle --
that, psychologically, we are living fossils of our Stone Age
ancestors.3 Accordingly, the evolved nature of the human mind is
allegedly discoverable by "reverse engineering" the mind from the
vantage of our Pleistocene past -- figuring out the adaptive problems
our ancestors faced and then hypothesizing the modules that evolved to
Despite being an ardent fan of evolutionary psychology, I'm deeply
skeptical about the Evolutionary Psychology paradigm. One problem
concerns EP's claim that the human mind is massively modular. Our best
evidence indicates, instead, that the human mind is adapted to adapt
to highly variable and often rapidly changing environments.5 Our
species' great cognitive achievement was not the evolution of a legion
of idiots savants, but the evolution of cortical plasticity, which
enables the brain to reorganize itself in response to changing
epistemic demands. In this respect, the brain is very similar to the
immune system, which manufactures antibodies as needed in response to
changing pathogenic demands.6
A second problem concerns the doctrine that our minds are adapted to
the Stone Age. First, this idea greatly underestimates the rate at
which natural and sexual selection can drive evolutionary change.
Recent studies have demonstrated that selection can overhaul a
species' adaptations in as few as eighteen generations (for humans,
roughly 450 years). Second, the principal driving forces in human
psychological evolution have been the demands of competition and
cooperation with fellow humans. This created an arms race in human
psychological evolution, in which every bit of evolution in human
psychology changed the competitive and cooperative environments to
which human psychology needed to adapt. And this arms race accelerated
the rate of human psychological evolution. So there has undoubtedly
been significant human psychological evolution since the Pleistocene.
We're not simply Pleistocene hunter-gatherers, like Fred and Wilma
Flintstone, struggling to survive and reproduce in evolutionarily
novel suburban habitats.7
But this is all highly theoretical stuff. Nothing persuades quite like
sound empirical results. And on this score EP has appeared very
persuasive. Indeed, EPists boast a number of impressive discoveries,
including a sex difference in mate preferences (that males prefer
nubility, while females prefer nobility), evolved strategies of
infidelity, a sex difference in jealousy, and the reason why
stepchildren suffer a high risk of maltreatment. All of these claims
have received tremendous media attention, and the coverage has made it
appear that these "discoveries" have unassailable evidence in their
favor. But a closer look at the evidence reveals ample grounds for
skepticism regarding EP's claims about the nature of the mind. Indeed,
there isn't unequivocal evidence to support EP's most highly
publicized "discoveries." In what follows, I will focus on three of
the most widely cited claims (presented in much greater detail in my
recently published book, Adapting Minds).
Her Cheating Mind
In Alfred Kinsey's classic sex surveys, 50% of married men, and 26% of
married women, reported having had extramarital sex.8 Why? According
to EP, since a man's maximum potential lifetime reproductive output is
limited only by the number of pregnancies he can cause, every
extramarital encounter represents another potential offspring. But a
woman's maximum potential lifetime reproductive output is limited by
the number of pregnancies she can carry to term, and a single mate can
provide a woman with all the sperm she needs for those pregnancies.
So, EPists ask, what reproductive benefits do women gain from
David Buss claims to have the answer: while women can't increase the
quantity of their offspring through extramarital affairs, as men can,
they can increase the quality of their offspring. A woman can harvest
"good genes" from an extramarital sex partner, and those good genes
can provide her offspring with better health, superior disease
resistance, and greater attractiveness to the opposite sex. Moreover,
as long as she keeps the affair concealed, a woman who has an
extramarital affair with a male with good genes gets the reproductive
benefits of both worlds: She obtains superior genes for a child who
can then be reared on the resources provided by her cuckolded
long-term mate with inferior genes. "Some women pursue a `mixed'
mating strategy," says Buss, "ensuring devotion and investment from
one man while acquiring good genes from another."9
Because of the reproductive payoffs of this "mixed" mating strategy,
women evolved a "psychology of infidelity,"10 or "a psychological
mechanism in women specifically designed to promote short-term mating"
when resources have already been secured from a long-term mate, the
short-term extrapair sex is likely to go undetected, and the extrapair
partner has better genes than the long-term mate.11 The mechanism that
promotes extrapair sex under these conditions is, according to Buss, a
female psychological adaptation.
Three findings provide the core evidence for Buss's claim that female
short-term infidelity is an adaptation. First, an interesting study
found that, on average, the more symmetrical a male, the higher his
attractiveness rating by female panelists.12 This is significant
because many biologists believe symmetry (in which the two sides of
the body are mirror images of one another) is a sign of developmental
stability, an ability to resist the harmful effects of pathogens and
minor mutations. The study also found that highly symmetrical men, on
average, reported having been chosen by women as an extrapair sexual
partner more often than less symmetrical men. And this, Buss claims,
shows that women prefer extrapair partners with good genes.
In another experiment, T-shirts were washed in unscented laundry
detergent and issued to male participants who were required to sleep
in them for two consecutive nights.13 During the two-day period, the
males were to refrain from using scented soaps, eating spicy foods,
drinking alcohol, smoking, and having sex. After the two days, female
subjects smelled the T-shirts both during ovulation and during the
infertile phase of their menstrual cycles, and they rated each T-shirt
for "pleasantness" and "sexiness" of smell. The scents of the T-shirts
of highly symmetrical men were rated highest -- but only by women who
were ovulating. Buss concludes that "women detect the scent of
symmetry, prefer that scent when ovulating, and choose more
symmetrical men as affair partners."14
Third, in a British study, women who reported extrapair involvements
also reported that approximately 60% of their copulations during the
fertile phase of their menstrual cycles took place with their
extrapair partners, whereas about 60% of their copulations during the
infertile phase of their cycles took place with their in-pair
partners.15 So, when women have affairs, the majority of their sexual
activity when they are fertile occurs with their affair partners,
which tips the odds of paternity in favor of the extrapair partner.
Buss argues that these findings provide rather definitive support for
the following picture: women have a long-term mating psychology, which
leads them to seek a long-term mate who will provide resources. But,
once they've landed such a mate, women can become motivated by a
psychological mechanism that is "specifically designed to promote
short-term mating," and this will motivate extramarital affairs with
males with good genes.
However, the claim that women have a psychological adaptation
"specifically designed to promote short-term" infidelity goes well
beyond the evidence. In fact, the pattern of female short-term
infidelity described by Buss is best explained as a byproduct of other
psychological and physiological adaptations, rather than as a direct
result of an adaptation specifically for short-term infidelity.
Let's begin with the question of why women cheat at all. A number of
studies, conducted over decades, have consistently found that sexual
dissatisfaction in marriage is the leading factor in causing women to
engage in short-term extramarital sexual affairs,16 and these results
have recently been corroborated by EPists.17 Indeed, although women
who are emotionally dissatisfied in marriage seek extramarital
emotional involvements, they are not more likely than satisfied women
to have extramarital sexual affairs; only sexually dissatisfied women
are more likely to have extramarital sexual involvements.18 Moreover,
women who are sexually dissatisfied in marriage have been found to be
over twice as likely as sexually satisfied women to have extramarital
sex.19 Accordingly, the fact that women engage in short-term
extramarital affairs can be explained simply as resulting from a
frustrated "sex drive" (for lack of a better term). When the "sex
drive" is going unsatisfied in marriage, women sometimes seek sexual
satisfaction outside marriage. This may have reproductive benefits,
but it is explicable without appeal to a mechanism specifically
designed to harvest "good genes" from an extrapair partner.
Of course, while this may explain why women take extramarital sex
partners, it doesn't explain why their sexual activity with their
extrapair partners increases during the fertile phase of their
menstrual cycles. But several studies have consistently found a peak
in the levels of female desire for sex, fantasy about sex,
masturbation, and initiation of sex during the fertile phase of the
menstrual cycle.20 The rise in female desire and female-initiated
sexual activity during the fertile phase is probably an adaptation,
since it is too well designed for reproduction to be an accident or
byproduct of something else. So, the increase in sexual activity with
extrapair partners during the fertile phase of the menstrual cycle is
really just a byproduct of a generalized increase in female-initiated
sexual activity during that period.
Buss is aware of this research, but argues that it can't explain the
facts about female short-term infidelity, since it was only sexual
activity with extrapair partners, not sexual activity in general, that
was found to increase during the fertile phase. But the reason for
this extrapair bias is relatively mundane. First, the large majority
of women who have extramarital sexual affairs are sexually
dissatisfied in their marriages. Second, if a sexually dissatisfied
married woman is seeking sexual satisfaction through an extrapair
involvement, she will be unlikely to repeat extrapair sexual
encounters with men who fail to satisfy, since there are potential
costs to getting caught in an infidelity. So, any male who is a
regular extrapair partner of a married woman is very likely a man with
whom sex is gratifying in a way it is not with her husband. Therefore,
when a woman experiences an increased desire for sex during the
fertile phase of her cycle, she is far more likely to arrange to have
satisfying sex with her extrapair partner than to have unsatisfying
sex with her husband.
Still, EPists will argue, none of this explains why women tend to
choose symmetrical men as their extrapair partners. But, again, this
is merely a byproduct of more general mate preferences. By Buss's
theory, symmetry is one of the things that women seek in a long-term
mate because it supposedly signals "good genes." Even if women have an
evolved preference for symmetrical men, this preference may be part of
a single set of mate preferences, which is operative in choosing both
long-term and short-term mates. To illustrate, suppose that women seek
long-term mates who have only two qualities -- symmetry and a
willingness to provide resources. When a woman seeks a partner for a
short-term infidelity, the same preference structure could be
operative, but resources become irrelevant. When resources drop out of
the equation, only the preference for symmetry remains.
Here, then, is the byproduct explanation of female short-term
infidelity. Suppose that women possess the following three
adaptations, among others: the "sex drive" (the desire for a regular
and fulfilling sex life, together with the patterns of planning and
acting so as to ensure the satisfaction of that desire), a peak in
sexual desire during the fertile phase of the menstrual cycle (with
its attendant increase in female-initiated sexual activity), and a
preference for symmetrical males (which is one of several mate
preferences). When a woman is sexually dissatisfied in her marriage,
she is more likely to begin an extramarital sexual involvement
(because of the "sex drive"). In selecting an extrapair partner, the
same preferences that were operative in choosing a long-term mate will
also be operative, but some of them (for example, a willingness to
provide resources) will be irrelevant to the specifically sexual role
for which the extrapair partner is being selected. As irrelevant
preferences drop out of the selection process, the preference for
symmetry comes to loom large, so women will tend to choose symmetrical
men as extrapair partners. Then, once a woman begins an extramarital
affair, her peaking desire for sex during the fertile phase of her
menstrual cycle causes an increase in the number of sexual encounters
that she initiates. And, because sex with her husband is less
gratifying than sex with her affair partner, the sexual encounters she
initiates will be almost exclusively with her extrapair partner, so
that sex with her highly symmetrical affair partner will be
concentrated during the fertile phase of her menstrual cycle. In this
way, the above three adaptations can conspire under circumstances of
sexual dissatisfaction in marriage to produce a pattern of behavior
that appears to be the direct result of an adaptation specifically for
short-term infidelity. So the available evidence doesn't provide
convincing support for the claim that women have an evolved
psychological mechanism specifically for strategic infidelity.
His Sexual Jealousy
According to Buss, jealousy is a psychological adaptation, an
emotional alarm that is designed to go off whenever we detect signs of
a partner's potential infidelity and to mobilize us to avoid or
minimize our reproductive losses. I believe that this hypothesis is
one of EP's significant contributions to our understanding of the
human mind. But Buss doesn't stop here. He further argues that, since
men and women faced different threats to reproductive interests
throughout human evolutionary history, the sexes have evolved distinct
jealousy mechanisms, which "contain dedicated design features, each
corresponding to the specific sex-linked adaptive problems that have
recurred over thousands of generations of human evolutionary history"
(Buss et al., 1999, p. 126). It is a woman's sexual infidelity, Buss
argues, that threatens a man's reproductive interests by undermining
his confidence in paternity and putting him at risk of investing his
resources in another man's offspring. A woman's reproductive
interests, in contrast, are threatened by a male's emotional
involvement with another woman, since that potentially entails a loss
of his resources. Thus, Buss hypothesizes, women's jealousy "is
triggered by cues to the possible diversion of their mate's investment
to another woman, whereas men's jealousy is triggered primarily by
cues to the possible diversions of their mate's sexual favors to
To test for a sex difference in jealousy, Buss and his colleagues
(1992) designed the following questionnaire. This questionnaire, or a
minor variant of it, was then administered to subjects in six
Instructions: Please think of a serious committed romantic
relationship that you have had in the past, that you currently
have, or that you would like to have. Imagine that you discover
that the person with whom you've been seriously involved became
interested in someone else. What would distress or upset you more
(please circle only one):
(A) Imagining your partner forming a deep emotional attachment to that
person [emotional infidelity].
(B) Imagining your partner enjoying passionate sexual intercourse with
that other person [sexual infidelity].
(A) Imagining your partner trying different sexual positions with that
other person [sexual infidelity].
(B) Imagining your partner falling in love with that other person
The principal data that Buss cites in support of this theory are
responses to forced-choice questionnaires that have been administered
in six cultures (Box 1). These data show that significantly more men
than women report that the thought of a partner's sexual infidelity is
more distressing than the thought of a partner's extrapair emotional
involvement. In no study did more women than men report sexual
infidelity to be more upsetting than emotional infidelity. Indeed, on
average, across all studies, many more men than women reported sexual
infidelity to be more upsetting than emotional infidelity -- 51% of
the men versus 22% of the women in response to Dilemma 1 (Table 1),
and 38% of the men versus 13% of the women in response to Dilemma 2
table 1. percentage choosing (B) sexual infidelity as more upsetting in
Dilemma 1 (by survey sample)
USA USA USA USA USA USA
(Buss et al.1992)28 (Buss et al. 1999)22 (Buunk et al. 1996)31
(DeSteno & Salovey 1996a)29 (Geary et al. 1995)54 (Pietrzak et al.
Male 60 76 61 55 53 73
Female 17 32 18 32 23 4
China Netherlands Germany Korea Japan Average
(Geary et al. 1995)54 (Buunk et al. 1996)31 (Buunk et al. 1996)31
(Buss et al.1999)22 (Buss et al. 1999)22
Male 21 51 28 59 38 51
Female 5 31 16 18 13 22
But these results don't actually confirm Buss's theory. Buss claims
that male jealousy will "focus on cues to sexual infidelity because a
long-term partner's sexual infidelity jeopardizes his certainty of
paternity," whereas female jealousy will focus on cues to emotional
infidelity because of potential loss of parental resources.22 To
confirm Buss's theory, it's necessary to confirm these predictions --
to confirm, for example, that males care more about sexual infidelity
than they do about emotional infidelity, not simply that they care
more about sexual infidelity than females do. But the data do not show
this. Indeed, on average, only half of male subjects chose sexual
infidelity as more distressing than emotional infidelity in response
to Dilemma 1 (Table 1), and a full 62% chose emotional infidelity over
sexual infidelity in response to Dilemma 2 (Table 2).
table 2. percentage choosing (A) sexual infidelity as more upsetting in
Dilemma 2 (by survey sample)
USA USA USA USA
(Buss et al. 1992)28 (Buss et al. 1999)22 (Buunk et al. 1996)31
(Harris & Christenfeld 1996a)29
Male 44 43 44 47
Female 12 11 12 12
Netherlands Germany Korea Japan Average
(Buunk et al. 1996)31 (Buunk et al. 1996)31 (Buss et al. 1999)22 (Buss
et al. 1999)22
Male 23 30 53 32 38
Female 12 8 22 15 13
Moreover, there are some anomalous data for which Buss's theory can't
easily account. First, there is significant cultural variation in the
questionnaire results. While the percentages of males reporting sexual
infidelity to be more upsetting than emotional infidelity in response
to Dilemma 1 are as high as 76% in a U.S. sample and 59% in the Korean
sample, they are as low as 21% in the Chinese sample and 28% in the
German sample (Table 1). Similarly, although the percentages of males
selecting sexual infidelity in response to Dilemma 2 are as high as
47% in a U.S. sample and 53% in the Korean sample, they are as low as
23% in the Dutch sample and 30% in the German sample (Table 2). These
low-side outliers hardly support Buss' claim that male jealousy is
focused on cues of sexual infidelity and that this is true "across
Second, the results of three studies in which the infidelity dilemmas
were administered to homosexual men are difficult to reconcile with
Buss's claim that there is a sex difference in the evolved "design
features" of the psychological mechanisms of jealousy. In one study,
only 24% of homosexual men chose sexual infidelity as more upsetting
than emotional infidelity in Dilemma 1, and only 5% chose sexual
infidelity as more upsetting in Dilemma 2.24 Another study
administered only Dilemma 2 to a sample of homosexual men, of whom
only 13% chose sexual infidelity as more upsetting than emotional
infidelity.25 Finally, when both dilemmas were administered to both
homosexual and heterosexual men and women, it was found that
homosexual men were even less upset by sexual infidelity than were
Third, the psychologist Christine Harris found that, although
heterosexual males who were asked to imagine their partners' having
sex with another male showed greater physiological arousal than those
who were asked to imagine their partners' forming an emotional
attachment to another man, males who were asked to imagine having sex
with their own partners showed just as great a physiological arousal
as those imagining being cuckolded.27 Indeed, Harris found that there
was no significant difference between the one group's physiological
arousal in response to imagined sexual infidelity and the other
group's physiological arousal in response to imagined sexual
intercourse. This indicates that the results obtained by Buss and his
colleagues are confounded by the fact that males become more aroused
by imagining events with sexual content, in general, than by imagining
events with emotional content. And this is something that Buss himself
has admitted would undermine his theory.28
I believe that a more minimal hypothesis concerning the nature of our
evolved jealousy mechanism can better account for the data. I call it
the relationship jeopardy hypothesis, according to which both sexes
have the same evolved capacity to learn to distinguish threatening
from nonthreatening extrapair involvements and to experience jealousy
to a degree that is proportional to the perceived threat to a
relationship in which one has invested mating effort. This same
capacity leads to a common sex difference in how infidelities are
viewed, however, because the sexes acquire different beliefs about
opposite-sex sexual strategies. So the standard sex difference is a
product of typical differences in the information believed by the
sexes, not of a sex difference in the design of the mechanisms that
process that information.
Consider how the relationship jeopardy hypothesis accounts for the
data. According to the relationship jeopardy hypothesis, the sexes
differ in their acquired beliefs about infidelity, and a series of
studies found precisely that.29 These studies found that men believe
that, for women, sex implies love more than love implies sex and that
women believe that, for men, love implies sex more than sex implies
love. The most dramatic finding was that women believe that it is not
that likely that a man's having sex with a woman implies any kind of
emotional involvement with her. Given these beliefs, men should find
sexual infidelities more distressing than women because a female's
sexual infidelity signals a potential threat to a relationship (via
the likely combination with an emotional involvement) that is greater
than the potential threat signaled by a male's sexual infidelity
(which is likely not accompanied by an emotional involvement).
Moreover, as we saw earlier, women having extramarital sex are far
more likely to be dissatisfied in their marriages than unfaithful
men.30 So, even in the absence of an accompanying emotional
involvement, a woman's sexual infidelity is threatening because it
signals dissatisfaction in the relationship in a way that a man's
sexual infidelity does not. Thus, if both sexes have the same evolved
capacity to distinguish threatening from nonthreatening infidelities
and respond accordingly, we should expect men to find emotional
infidelities very threatening, but we should also expect men to find
sexual infidelities more threatening to a relationship than women find
them. And Buss's questionnaire results show both effects.
In addition, if the relationship jeopardy hypothesis is correct, if
there are cultural differences in the degree to which sexual
infidelity is correlated with desertion, then the members of a culture
in which there is a weaker correlation between sexual infidelity and
desertion should be less bothered by sexual infidelity than the
members of a culture in which the correlation is stronger.
Interestingly, Buss and his colleagues noted that the German and Dutch
"cultures have more relaxed attitudes about sexuality, including
extramarital sex, than does the American culture," and that in the
Netherlands "a majority feels extramarital sexual relationships are
acceptable under certain circumstances."31 Accordingly, German and
Dutch males should be less likely than American males to assume that a
female partner's sexual infidelity portends desertion, and
consequently they should be less distressed by sexual infidelity than
American males. And, on average, 61% of American males chose sexual
infidelity as more distressing than emotional infidelity in response
to Dilemma 1 (Table 1), and 44% chose sexual infidelity in Dilemma 2
(Table 2). In contrast, on average, only 40% of German and Dutch males
chose sexual infidelity in Dilemma 1 (Table 1), and only 26% chose
sexual infidelity in Dilemma 2 (Table 2).
Finally, when homosexual and heterosexual men and women were asked
their beliefs about relationships and infidelity, the only significant
correlation that emerged was between degree of distress over sexual
infidelity and the belief that sexual infidelity indicated likely
abandonment.32 All subjects -- whether men or women, whether
homosexual or heterosexual -- were far more likely to be distressed by
an imagined sexual infidelity if they believed that sexual infidelity
portends the end of a relationship. Further, heterosexual males were
by far the most likely to believe that a sexual infidelity is a likely
precursor to abandonment. Women, both homosexual and heterosexual,
were far more likely than heterosexual men to "discount" a sexual
infidelity as nonthreatening to a relationship, and homosexual men
were even more likely than women to discount a sexual infidelity as
nonthreatening. If these beliefs were processed by the mechanism
postulated by the relationship jeopardy hypothesis, it would generate
precisely the pattern of questionnaire responses from heterosexual men
and women Buss found, but also the responses of homosexual men
Thus, not only is there not good evidence of Buss's hypothesized sex
difference in the "design features" of the jealous mind, but Buss's
hypothesis doesn't easily account for a variety of data. In contrast,
a simpler hypothesis, according to which there is no sex difference in
the "design features" of the mind, but only in the beliefs typically
acquired by the sexes, better explains all the data.
His Abuse of Her Children
One of the "discoveries" that Pinker and Buss frequently tout as a
signature achievement of EP is the finding, by Martin Daly and Margo
Wilson, that children who live with stepparents are at a greater risk
of maltreatment than children who live with both genetic parents.33 An
evolutionary perspective on human psychology should lead us to expect
this, Daly and Wilson argue, because "parental investment is a
precious resource, and selection must favor those parental psyches
that do not squander it on nonrelatives."34
Daly and Wilson hypothesize that motivational mechanisms of parental
love have evolved to be triggered by (genetic) offspring during a
"critical period." Once triggered, parental love serves as "inhibition
against the use of dangerous tactics in conflict with the child."35
Since these evolved mechanisms of parental love, which inhibit
violence, aren't triggered in substitute (nongenetic) parents, "angry
lapses of parental solicitude" in conflictual situations more
frequently elicit "the use of dangerous tactics" from substitute
parents than from genetic parents.36 This leads Daly and Wilson to
what they call "the most obvious prediction from a Darwinian view of
parental motives": "Substitute parents will generally tend to care
less profoundly for children than natural parents, with the result
that children reared by people other than their natural parents will
be more often exploited and otherwise at risk."37 In particular, since
stepparenthood is the most common form of substitute parenthood, Daly
and Wilson expect stepchildren to be at greater risk than genetic
children. Even more particularly, since at least 80% of children
living in stepfamilies live with a stepfather and a genetic mother,38
Daly and Wilson expect that this elevated risk to stepchildren is due
to maltreatment at the hands of stepfathers.39
Daly and Wilson cite several studies as confirmation of this
prediction, but most provide only indirect evidence, since they lacked
important controls. The best direct evidence for this prediction is
Daly and Wilson's landmark 1985 study of 99 cases of child
maltreatment in the municipality of Hamilton-Wentworth in Ontario,
Canada, during a one-year period from 1982 to 1983.40 Daly and Wilson
found that children under the age of five who lived with a genetic
parent and a stepparent were 40.1 times more likely to be victims of
maltreatment than same-aged children who lived with both genetic
parents (Table 3). The relative risk to stepchildren aged five and up
dropped sharply, and even sharper for stepchildren aged eleven and up,
but in all age groups children living with a genetic parent and a
stepparent were at a significantly greater risk of becoming victims of
maltreatment than children living with both genetic parents.
table 3. maltreatment risk for children living with a stepparent and a
genetic parent, relative to children living with both genetic parents, by
child's age (Hamilton-Wentworth, 1982-1983).
Child's age when maltreated 0-4 yrs. 5-10 yrs. 11-17 yrs.
Times a child with one stepparent is more likely to be maltreated
compared to those with both genetic parents 40.1 19.4 9.8
There are, however, three shortcomings of Daly and Wilson's study.
First, Daly and Wilson's sample consisted of 99 cases of maltreatment,
which included not only physical abuse (inflicted injury), but 21
cases of sexual abuse and an unreported number of "unintentional
omissions" considered neglect by a child welfare professional. But
sexual abuse and physical abuse appear to be distinct phenomena with
distinct etiologies. Indeed, intrafamilial child sexual abuse is
rarely accompanied by physical abuse,41 so it doesn't consist in "the
use of dangerous tactics in conflict with the child." Moreover, in the
U.S., the class of "unintentional omissions" often includes allowing
truancy and failing to secure a child with a seat belt.42 These also
don't involve "the use of dangerous tactics in conflict" situations.
Since Daly and Wilson claim that stepchildren are at greater risk
because the "inhibition against the use of dangerous tactics in
conflict" is not triggered in stepparents, cases of maltreatment that
don't involve the use of dangerous tactics in conflict don't belong in
the sample against which to test their prediction. If we want to
understand the "lapses of parental love" that result in "the use of
dangerous tactics in conflict with the child," as Daly and Wilson
claim, we should explore data regarding physical abuse, rather than
the amorphous category of maltreatment, to test whether substitute
parents are more physically abusive than genetic parents.
In order to test Daly and Wilson's prediction against a much larger
and far more representative sample of cases of physical abuse, Elliott
Smith, the Associate Director of the National Data Archive on Child
Abuse and Neglect, and I analyzed child abuse data compiled in the
Third National Incidence Study of Child Abuse and Neglect (NIS-3). We
found that children under the age of five living in a stepfamily were
8.2 times more likely to be physically abused than same-aged children
living with both genetic parents (Table 4), which is drastically lower
than the 40-times-greater risk of maltreatment that Daly and Wilson
found. And children aged five and above who lived in a stepfamily were
only 3.3 times more likely to be physically abused than same-aged
children living with both genetic parents.
table 4. rates of physical abuse (per thousand children) by household
composition, NIS-3 (United States, 1993)
Child's age when maltreated 0-4 yrs. 5-10 yrs. 11-17 yrs. Overall
Rate of abuse per 1,000 for two genetic parents 1.7 3.2 3.1 2.7
Rate of abuse per 1,000 for one genetic parent plus one stepparent
13.9 10.2 10.5 10.7
While not as dramatic as Daly and Wilson's findings, these results
nonetheless appear to confirm Daly and Wilson's prediction. But this
brings us to the second methodological shortcoming of Daly and
Wilson's study. Daly and Wilson's data concern the risk of
maltreatment to children living in households of varying parental
composition, rather than a child's risk of being maltreated by a
stepparent or genetic parent. That is, Daly and Wilson's data don't
identify the perpetrators of maltreatment, even though their
hypothesis predicts that stepfathers will be disproportionately
represented among perpetrators. Since the NIS-3 data identified
perpetrators, they allow a more direct test of Daly and Wilson's
prediction, and those data yield two surprises. First, in a clear
anomaly for Daly and Wilson's hypothesis, single genetic fathers were
actually 1.7 times more likely than stepfathers to physically abuse
their children (Table 5). Second, the data on physical abuse of
children living with a genetic mother and a stepfather show that
genetic mothers are involved in a significant portion of that abuse,
either acting alone or in concert with the stepfather (Table 6).
table 5. rates of physical abuse (per thousand children) by a father acting
alone, NIS-3 (United States, 1993)
Child's age when maltreated 0-4 yrs. 5-10 yrs. 11-17 yrs. Overall
Parents in household genetic father only 19.8 9.8 10.1 11.4
Parents in household genetic mother plus stepfather 11.1 7.1 6.1 6.8
table 6. rates of physical abuse (per thousand children) in genetic
mother-stepfather households, NIS-3 (United States, 1993)
Child's age when maltreated 0-4 yrs. 5-10 yrs. 11-17 yrs. Overall
Perpetrator: genetic mother acting alone 1.6 0.8 1.91.5
Perpetrator: stepfather acting alone 11.1 7.1 6.16.8
Perpetrator: both parents4.8 1.9 3.83.2
Nonetheless, children who were abused by a parent acting alone were
4.5 times more likely to be abused by their stepfather than by their
genetic mother (Table 6), and this does appear to confirm Daly and
Wilson's prediction. But this brings us to the third of the
methodological shortcomings of Daly and Wilson's study, which is a
shortcoming of our NIS-3 study as well. Daly and Wilson's sample and
the NIS-3 sample consisted entirely of officially reported cases of
child maltreatment -- that is, cases of maltreatment that were brought
to the attention of a professional who worked in a capacity concerned
with child welfare, were investigated in some way by that professional
or others to whom the cases were referred, and were determined to be
genuine cases of child maltreatment by the investigators. But some
family violence researchers have pointed out that child welfare
professionals sometimes take the presence of a stepparent in the
household into consideration in deciding whether a bruise or broken
bone resulted from an accident or abuse.43 That is, many child welfare
professionals take the presence of a stepparent in a household to be
partly diagnostic of maltreatment. So, Gelles and Harrop argue,
"injuries to children with non-genetic parents are more likely to be
diagnosed and reported as abuse."44 As a result, official case reports
of child maltreatment may contain a bias against stepparents, which
distorts the facts concerning the relative rates of maltreatment by
stepparents and genetic parents.
Daly and Wilson are fully aware of the potentially confounding effects
of diagnostic bias on their studies, but they dismiss it with the
following single argument: "If reporting or detection biases were
responsible for the overrepresentation of stepparents among child
abusers, then we would expect the bias, and hence the
overrepresentation, to diminish as we focused upon increasingly severe
and unequivocal maltreatment up to the extreme of fatal batterings."45
"At the limit," they argue, "we can be reasonably confident that child
murders are usually detected and recorded."46 When Daly and Wilson
examined "validated" cases of child homicide in America47 and cases of
child homicide in Canada that were "known to Canadian police,"48 they
found that stepchildren were far more likely to be victims of fatal
maltreatment than children living with both genetic parents. Thus,
Daly and Wilson conclude that comparable findings regarding non-fatal
maltreatment are not confounded by a reporting bias against
There is substantial evidence, however, that "validated" child
homicides and those "known to police" are but a partial record of
child maltreatment fatalities in the United States, and there is
little reason for doubting that Canada is similar in this regard.
Indeed, when review boards undertook comprehensive studies of up to
nine sources of information about each child fatality in four U.S.
states, they consistently found that only 40-50% of all identifiable
child maltreatment fatalities, including inflicted injury fatalities,
were coded as maltreatment fatalities on death certificates or in
police records.49 The remainder were coded as accidental deaths or,
more commonly, deaths due to an "undetermined manner."
More importantly, analysis of Colorado records revealed direct
evidence of a potential diagnostic bias against "stepfathers."50 For
maltreatment fatalities at the hands of "other relatives," which
included legally married stepfathers, were 1.37 times more likely to
be recorded as maltreatment fatalities on death certificates than were
maltreatment fatalities perpetrated by genetic parents. Moreover,
maltreatment fatalities at the hands of "other unrelated" individuals,
which included "live-in boyfriends" of victims' mothers, were 8.71
times more likely to be recorded as such on death certificates than
maltreatment fatalities at the hands of genetic parents. This last
fact is particularly important for two reasons. First, Daly and Wilson
classified "live-in boyfriends" as stepfathers (as did Smith and I).51
Second, in the Canadian filicide data mentioned above, Daly and Wilson
found that "common-law" stepfathers accounted for a full 89% of the
filicides that were attributed to stepfathers in police records.52
Thus, "common-law" stepfathers, who almost single-handedly accounted
for the higher rate of filicide among stepfathers in Daly and Wilson's
study, were in a group that is 8.71 times more likely than genetic
parents to have a perpetrated child maltreatment fatality actually
identified as a maltreatment fatality in official records.
If, as Daly and Wilson argue, the effects of any reporting bias should
be less in cases of fatal maltreatment than in cases of non-fatal
abuse, this degree of reporting bias in U.S. cases of fatal
maltreatment implies a higher degree of reporting bias in cases of
non-fatal abuse, which is then more than sufficient to account for the
overrepresentation of stepchildren in the NIS-3 data (Table 4). So,
available evidence indicates that American physical abuse data are
sufficiently confounded by reporting bias that they can't confirm Daly
and Wilson's hypothesis, and there is little reason to think that the
Canadian records are immune to this problem. Since all of our evidence
to date concerning stepparental abuse derives from official case
reports, we simply don't know whether stepparents are more likely than
genetic parents to abuse their children. Daly and Wilson's claim that
stepparents are more likely than genetic parents to abuse their
children goes beyond the available reliable evidence.
I've argued that some of the principal pieces of evidence cited in
support of three of Evolutionary Psychology's highly publicized
"discoveries" in fact fail to establish EP's claims. And I argue in
Adapting Minds that other evidence cited in support of these
"discoveries" suffers similar evidentiary problems. EP's other
"discoveries" enjoy no better empirical support. For example, I argue
in Adapting Minds that the evidence fails to establish Buss's claims
about evolved mate preferences (that males are fixated on nubility,
while females are fixated on nobility) and Cosmides' claim that we
have an evolved module for detecting cheaters in social exchanges.53
Although EP is a bold and innovative explanatory paradigm, it has not
provided convincing evidence for its claims about the nature and
evolution of human psychology. We really don't yet know how to
understand human psychology from an evolutionary perspective. Perhaps
some day we will achieve that understanding, but that day is not at
hand. Coming to terms with the shortcomings of Evolutionary
Psychology, however, may help us eventually achieve a new and improved
1. Caporael, Linnda R. 2001. "Evolutionary Psychology: Toward a
Unifying Theory and a Hybrid Science." Annual Review of Psychology
2. Cosmides, Leda, and John Tooby (1997). The Modular Nature of Human
Intelligence. In A. B. Scheibel and J. W. Schopf (Eds.), The
Origin and Evolution of Intelligence (pp. 71-101). Sudbury, MA:
Jones and Bartlett.;
Pinker, Steven. 1997. How the Mind Works. New York: W. W. Norton.;
Tooby, John, and Leda Cosmides (2000). Toward Mapping the Evolved
Functional Organization of the Mind and Brain. In M. S. Gazzaniga
(Ed.), The New Cognitive Neuro-sciences (second ed., pp.
1167-1178). Cam-bridge, MA: MIT Press.
3. Tooby, John, and Leda Cosmides. 1990. "The Past Explains the
Present: Emotional Adaptations and the Structure of Ancestral
Environments." Ethology and Sociobiology 11: 375-424.
4. Tooby, John, and Leda Cosmides. 1992. "The Psychological
Foundations of Culture." In J. H. Barkow, L. Cosmides and J. Tooby
(Eds.), The Adapted Mind: Evolutionary Psychology and the
Generation of Culture (pp. 19-136). New York: Oxford University
5. Sterelny, Kim. 2003. Thought in a Hostile World: The Evolution of
Human Cognition. Malden, MA: Blackwell.
6. Buller, David J. 2005. Adapting Minds: Evolutionary Psychology and
the Persistent Quest for Human Nature. Cambridge, MA: MIT Press,
7. Buller, 2005, chapter 3.
8. Kinsey, Alfred C., Wardell B. Pomeroy, and Clyde E. Martin. 1948.
Sexual Behavior in the Human Male. Philadelphia: W. B. Saunders.;
Kinsey, Alfred C., Wardell B. Pomeroy, Clyde E. Martin, and Paul
H. Gebhard. 1953. Sexual Behavior in the Human Female.
Philadelphia: W. B. Saunders.
9. Buss, David M. 2000. The Dangerous Passion: Why Jealousy Is as
Necessary as Love and Sex. New York: Free Press, 162.
10. Buss 2000, 159.
11. Greiling, Heide, and David M. Buss. 2000. "Women's Sexual
Strategies: The Hidden Dimension of Extra-Pair Mating."
Personality and Individual Differences 28: 929-963, 960.
12. Gangestad, Steven W., and Randy Thornhill. 1997. "The Evolutionary
Psychology of Extrapair Sex: The Role of Fluctuating Asymmetry."
Evolution and Human Behavior 18: 69-88.
13. Thornhill, Randy, and Steven W. Gangestad. 1999. "The Scent of
Symmetry: A Human Sex Pheromone That Signals Fitness?" Evolution
and Human Behavior 20: 175-201.
14. Buss 2000, 162.
15. Baker, R. Robin, and Mark A. Bellis. 1993. "Human Sperm
Competition: Ejaculate Manipulation by Females and a Function for
the Female Orgasm." Animal Behaviour 46: 887-909.
16. Terman, Lewis M. 1938. Psychological Factors in Marital Happiness.
New York: McGraw-Hill.;
Chesser, Eustace. 1956. The Sexual, Marital and Family
Relationships of the English Woman. London: Hutchinson's Medical
Bell, Robert R., and Dorthyann Peltz. 1974. "Extramarital Sex
among Women." Medical Aspects of Human Sexuality 8: 10-31.;
Tavris, Carol, and Susan Sadd. 1975. The Redbook Report on Female
Sexuality. New York: Delacorte.;
Glass, Shirley P., and Thomas L. Wright. 1985. "Sex Differences in
Type of Extramarital Involvement and Marital Dissatisfaction." Sex
Roles 12: 1101-1120.;
Glass, Shirley P., and Thomas L. Wright. 1992. "Justifications for
Extramarital Relationships: The Association between Attitudes,
Behaviors, and Gender." Journal of Sex Research 29: 361-387.;
17. Greiling and Buss 2000.
18. Glass and Wright 1985, 1992.
19. Bell and Peltz 1974; Tavris and Sadd 1975.
20. Adams, David B., Alice Ross Gold, and Anne D. Burt. 1978. "Rise in
Female-Initiated Sexual Activity at Ovulation and Its Suppression
by Oral Contraceptives." New England Journal of Medicine 299:
Hill, Elizabeth M. 1988. "The Menstrual Cycle and Components of
Human Female Sexual Behaviour." Journal of Social and Biological
Structures 11: 443-455.;
Stanislaw, Harold, and Frank J. Rice. 1988. "Correlation between
Sexual Desire and Menstrual Cycle Characteristics." Archives of
Sexual Behavior 17: 499-508.;
Regan, Pamela C. 1996. "Rhythms of Desire: The Association between
Menstrual Cycle Phases and Female Sexual Desire." Canadian Journal
of Human Sexuality 5: 145-156.
21. Buss, David M. 1994. The Evolution of Desire: Strategies of Human
Mating. New York: Basic Books, 128.
22. Buss, David M., Todd K. Shackelford, Lee A. Kirkpatrick, Jae C.
Choe, Hang K. Lim, Mariko Hasegawa, et al. 1999. "Jealousy and the
Nature of Beliefs About Infidelity: Tests of Competing Hypotheses
About Sex Differences in the United States, Korea, and Japan."
Personal Relationships 6: 125-150, 125.
23. Buss, David M. 1999. Evolutionary Psychology: The New Science of
the Mind. Boston: Allyn and Bacon, 326.
24. Sheets, Virgil L., and Marlow D. Wolfe. 2001. "Sexual Jealousy in
Heterosexuals, Lesbians, and Gays." Sex Roles 44: 255-276.
25. Harris, Christine R. 2002. "Sexual and Romantic Jealousy in
Heterosexual and Homosexual Adults." Psychological Science 13:
26. Bailey, J. Michael, Steven Gaulin, Yvonne Agyei, and Brian A.
Gladue. 1994. "Effects of Gender and Sexual Orientation on
Evolutionarily Relevant Aspects of Human Mating Psychology."
Journal of Personality and Social Psychology 66: 1081-1093.
27. Harris, Christine R. 2000. "Psychophysiological Responses to
Imagined Infidelity: The Specific Innate Modular View of Jealousy
Reconsidered." Journal of Personality and Social Psychology 78:
28. Buss, David M., Randy J. Larsen, Drew Westen, and Jennifer
Semmelroth. 1992. "Sex Differences in Jealousy: Evolution,
Physiology, and Psychology." Psychological Science 3: 251-255,
29. DeSteno, David A., and Peter Salovey. 1996a. "Evolutionary Origins
of Sex Differences in Jealousy?" Psychological Science 7:
DeSteno, David A., and Peter Salovey. 1996b. "Genes, Jealousy, and
the Replication of Misspecified Models." Psychological Science 7:
Harris, Christine R., and Nicholas Christenfeld. 1996a. "Gender,
Jealousy, and Reason." Psychological Science 7: 364-366.;
Harris, Christine R., and Nicholas Christenfeld. 1996b. "Jealousy
and Rational Responses to Infidelity across Gender and Culture."
Psychological Science 7: 378-379.
30. Glass and Wright 1985, 1992.
31. Buunk, Bram P., Alois Angleitner, Viktor Oubaid, and David M.
Buss. 1996. "Sex Differences in Jealousy in Evolutionary and
Cultural Perspective: Tests from the Netherlands, Germany, and the
United States." Psychological Science 7: 359-363.
32. Sheets and Wolfe 2001.
33. Daly, Martin, and Margo Wilson. 1985. "Child Abuse and Other Risks
of Not Living with Both Parents." Ethology and Sociobiology 6:
34. Daly, Martin, and Margo Wilson. 1988. Homicide. New York: Aldine
de Gruyter, 83.
35. Ibid., 75.
37. Ibid., 83.
38. Daly, Martin, and Margo Wilson. 1994. "Some Differential
Attributes of Lethal Assaults on Small Children by Stepfathers
Versus Genetic Fathers." Ethology and Sociobiology 15: 207-217,
Buller, 2005, 389.
39. Daly, Martin, and Margo Wilson. 1999. The Truth About Cinderella:
A Darwinian View of Parental Love. New Haven, CT: Yale University
40. Daly and Wilson, 1985.
41. Parker, Hilda, and Seymour Parker. 1986. "Father-Daughter Sexual
Abuse: An Emerging Perspective." American Journal of
Orthopsychiatry 56: 531-549.
42. Christoffel, Katherine Kaufer, Peter C. Scheidt, Phyllis F. Agran,
Jess F. Kraus, Elizabeth McLoughlin, and Jerome A. Paulson. 1992.
"Standard Definitions for Childhood Injury Research: Excerpts of a
Conference Report." Pediatrics 89: 1027-1034.
43. Gelles, Richard J., and John W. Harrop. 1991. "The Risk of Abusive
Violence among Children with Non-Genetic Caretakers." Family
Relations 40: 78-83.;
Giles-Sims, Jean. 1997. "Current Knowledge About Child Abuse in
Stepfamilies." Marriage and Family Review 26: 215-230.;
Giles-Sims, Jean, and David Finkelhor. 1984. "Child Abuse in
Stepfamilies." Family Relations 33: 407-413.
44. Gelles, 1991, 79.
45. Daly and Wilson, 1988, 88.
46. Daly and Wilson, 1999, 31.
47. Daly and Wilson, 1988, 88-89.
48. Daly, Martin, and Margo Wilson. 2001. "An Assessment of Some
Proposed Exceptions to the Phenomenon of Nepotistic Discrimination
against Stepchildren." Annales Zoologici Fennici 38: 287-296, 291.
49. Christoffel, Katherine K., Nora K. Anzinger, and David A. Merrill.
1989. "Age-Related Patterns of Violent Death," Cook County,
Illinois, 1977 through 1982. American Journal of Diseases of
Children 143: 1403-1409.;
Ewigman, Bernard, Coleen Kivlahan, and Garland Land. 1993. "The
Missouri Child Fatality Study: Underreporting of Maltreatment
Fatalities among Children Younger Than Five Years of Age," 1983
through 1986. Pediatrics 91: 330-337.;
Herman-Giddens, Marcia E., Gail Brown, Sarah Verbiest, Pamela J.
Carlson, Elizabeth G. Hooten, Eleanor Howell, et al. 1999.
"Underascertainment of Child Abuse Mortality in the United
States." Journal of the American Medical Association 282(5):
Crume, Tessa L., Carolyn DiGuiseppi, Tim Byers, Andrew P.
Sirotnak, and Carol J. Garrett. 2002. "Underascertainment of Child
Maltreatment Fatalities by Death Certificates," 1990-1998.
Pediatrics 110(2): e18.
50. Crume et al. 2002.
51. Daly and Wilson, 1985.
52. Daly and Wilson, 2001, 291.
53. Cosmides, Leda. 1989. "The Logic of Social Exchange: Has Natural
Selection Shaped How Humans Reason? Studies with the Wason
Selection Task." Cognition 31: 187-276.
54. Geary, David C., Michael Rumsey, C. Christine Bow-Thomas, and Mary
K. Hoard. 1995. "Sexual Jealousy as a Facultative Trait: Evidence
from the Pattern of Sex Differences in Adults from China and the
United States." Ethology and Sociobiology 16: 355-383.
55. Pietrzak, Robert H., James D. Laird, David A. Stevens, and
Nicholas S. Thompson. 2002. "Sex Differences in Human Jealousy: A
Coordinated Study of Forced-Choice, Continuous Rating-Scale, and
Physiological Responses on the Same Subjects." Evolution and Human
Behavior 23: 83-94.
Frank Miele: Evolutionary Psychology is Here to Stay
(from Skeptic magazine Vol. 12, No 1)
A Response to Buller
"Adaptationism pervades every level of biological inquiry, and
always has, because at every level descriptions of relevant
phenomena are almost invariably functional descriptions. The only
scientifically coherent account of the origin of adaptations, and
hence the only scientifically coherent account of `function', is
evolution by selection."
-- Donald Symons
The opening motions in philosopher David J. Buller's case against
Evolutionary Psychology (EP) appeared on his web site,1 followed by
the major argument in his book, Adapting Minds.2 More recently, Buller
argued against leading evolutionary psychologists John Tooby and Leda
Cosmides, Martin Daly and Margot Wilson, and David Buss in the journal
Trends in Cognitive Science (TCS), which allowed them to respond to
Buller's critique.3 In his Skeptic article in this issue, Buller takes
his case to a more popular jurisdiction. His brief against EP has two
1. A general critique of the concept of the modular ("Swiss Army
Knife") model of the mind, which he describes as a core dogma of
EP. If this foundation crumbles, the entire edifice of
Evolutionary Psychology will fall.
2. A specific critique of the data used to support two "signature
achievements" of EP: Martin Daly and Margot Wilson's Cinderella
Effect; and David Buss's studies of male-female differences in
This article reviews the arguments and data for and against
Evolutionary Psychology, Buller's criticisms, and the responses to
How Modular is the Mind? Debate, Not Dogma
David Buller is "deeply skeptical" of what he calls EP's two "defining
doctrines." First, that the human mind is "massively modular,"
composed of a myriad of independent, special purpose
("domain-specific") modules, each evolved to help our ancestors
survive and reproduce during the hunter-gather period of human
evolution. Second, that no subsequent cognitive adaptations to novel
environments have occurred. According to Buller, evolutionary
psychologists think that we are "a legion of idiots savants" who
struggle to get by like "Fred and Wilma Flintstone" dumped out of a
time machine into modern suburbia.
Modularity and adaptation to novel environments are two of the central
debates, not dogmas, in EP. They are described in the textbook by
David Buss, one of the evolutionary psychologists whose work Buller
claims to have refuted. Interestingly, Buller cites Buss's first
edition, but not the second (2004), which updates the coverage of
The view that "humans must possess a large number of specialized
psychological mechanisms, each dedicated to solving specific adaptive
problems," Buss summarizes, is "widely accepted within the field of
evolutionary psychology and indeed lies at the foundation of
evolutionary approaches." However, he then quotes several evolutionary
psychologists who have "recently argued that in addition to these
specific mechanisms humans also have evolved several domain-general
mechanisms." His list of such general purpose processes includes:
"intelligence, concept formation, analogical reasoning, working
memory, and classical conditioning." Finally, Buss notes that we
"routinely solve ancient adaptive problems in highly novel ways" and
that "everyone recognizes that humans have been able to flourish in an
environment very different from that in which we evolved."
While he concludes that the specificity-generality debate remains an
open question, Buss emphasizes that no evolutionary psychologist has
ever claimed that domain-specific modules are hermetically sealed off
from each other by any neurocognitive firewalls. Rather, discovering
"the precise nature of information sharing" between modules lies at
the cutting edge of research.4
CSI Cinderella -- Buller's Critique of Daly & Wilson
Evolutionary psychologists Martin Daly and Margot Wilson have spent
over two decades studying the nature of nurturing from an evolutionary
viewpoint. Based on Darwinian theory they hypothesized the "Cinderella
Effect" -- children living with stepparents would be far more likely
to be abused than would children living with both genetic parents.
They reasoned that in species like ours that provide substantial
parental care, evolution would select for nurturing behavior that was
directed toward genetic, rather than non-genetic, children in order to
increase their odds of reaching maturity and reproducing. In the cold
evolutionary calculus of Richard Dawkins' proverbial selfish gene,
"Why invest in a competitor's product?" All other things being equal,
the greater the degree of genetic relatedness, the greater probability
of helping and the lesser the probability of hurting someone else.
Neither Daly and Wilson nor any other evolutionary psychologists have
ever argued that this is the only factor causing child abuse. Rather,
they say it is the major factor in explaining human parenting. Nor
have they denied the role played by socioeconomic or cultural factors,
but instead have documented them.
The Cinderella Effect for lethal, non-lethal, and sexual abuse has
been verified not only by Daly and Wilson and their students, but by
other researchers as well, working in different countries, applying
various statistical methods and experimental designs, to a number of
independent datasets. On the flip side, selective caregiving to
genetic children over stepchildren has been documented as well. Daly
and Wilson have summarized just some of the research supporting the
Cinderella Effect in their responses to Buller, which I recapitulate
1. From infancy on, stepchildren suffer higher lethal and nonlethal
accident and injury rates, probably because they are less watched
over and protected.
2. Stepchildren leave home at a higher rate, at a younger age, and
more often give family conflict as their reason.
3. Parents were five times more likely to provide their genetic
children with money for college than their stepchildren.
4. In Britain, both mothers and stepfathers expressed even lower
aspirations for their stepchildren's education than did poorer
5. Stepchildren in Dominica suffer reduced growth and higher stress
hormone levels than age mates living with their genetic parents in
the same village and material conditions.
6. In Trinidad, village stepfathers spend significantly less time
with their children than genetic fathers and many more of their
interactions are nasty.
7. Hunter-gatherer stepfathers in Tanzania watch over their
stepchildren in camp, but unlike genetic fathers, never play with
Buller lists three "serious shortcomings" in the research by Daly and
Wilson. Together, he says, they "conspire to cast doubt" on the
reality of the Cinderella Effect.
First, Buller states that while the best evidence for the Cinderella
Effect comes from their "landmark 1985 study," Daly and Wilson went
wrong by lumping physical abuse, sexual abuse, and neglect together
into a single category of abuse. He counters their results with those
from his own analysis of the Third National Incidence Study of Child
Abuse and Neglect (NIS-3). While Daly and Wilson found that children
under five who lived with a genetic parent and a stepparent were 40
times more likely to suffer abuse than those living with both genetic
parents, his NIS-3 data show that they were only 3.3 times more likely
to be abused. Buller concedes that this still shows a Cinderella
Effect, but a much smaller one. (Note, however, Daly and Wilson's data
are from Canada, Buller's from the U.S. Reporting procedures and
protocols are quite different in the two countries.)
Next, Buller criticizes the fact that Daly and Wilson analyzed their
data by households, not by identity of the perpetrator. The NIS-3 data
do. How can we be sure that the abuse in the Canadian studies was
really committed by the stepfathers and not the genetic mothers? (It's
much less common for children to live with their genetic fathers and
stepmothers). This allows Buller to expose what he says is "a clear
anomaly for Daly and Wilson's hypothesis, single genetic fathers were
1.7 times more likely than stepfathers to physically abuse their
children." (Rightmost column in Buller's Table 5: 11.4/6.8 ~= 1.7).
Were Daly and Wilson unaware of the issue of failing to ID the perps
or the increased risk of abuse for children living with only one
genetic parent? Have they avoided them in order to bolster the
Cinderella Effect? Clearly not. Both are spelled out in an article
that Daly and Wilson published as far back as 1981!6
First they explain that:
We present the data in terms of household composition rather than
perpetrator for several reasons. While stepparents are relatively
frequent perpetrators of abuse, so to a lesser extent are natural
parents with stepparent spouses. The labelled "perpetrator" is not
necessarily the instigator, and moreover, one party may assume
responsibility to protect another. In the case of neglect,
identification of a single perpetrator seems inappropriate. For
these reasons, household composition is the more reliable datum.7
In this 1981 article, Figure 24-1 clearly shows that "Father-only is
much the riskiest situation."8 To my knowledge, Daly and Wilson were
the first to document this. As they state in their abstract, while
socioeconomic, psycho-pathological, and developmental factors all play
a role in explaining child abuse, "an evolutionary perspective may
provide a more encompassing view of circumstances exacerbating the
risk of abuse and neglect and of the ultimate rational for variations
in parental solicitude and negligence."9
While conceding that his own analysis of the NIS-3 data "does appear
to confirm" (emphasis added) the Cinderella Effect, Buller's third
criticism is that the officials who investigate abuse cases are biased
in attributing blame to stepparents while tending to dismiss charges
against biological parents. He supports this argument with the results
of a Colorado study, which showed that child fatalities caused by
abuse at the hands of "other relatives" (including stepfathers legally
married to the genetic mothers) were "1.37 times more likely to be
recorded as the result of maltreatment on death certificates" than
were those for genetic parents. This bias in reporting, Buller argues,
is sufficient to account for the mild Cinderella Effect that appears
to be present in the NIS-3 data.
Then where are the dead bodies? Daly and Wilson reply that if
stepfathers were always caught while genetic fathers usually get away
with it, "there would have to have been more than 500 undiscovered
paternal murders [in Canada] each year," above the average of 4 that
are detected, to make the two rates equal. In fact, "fewer than 400
Canadian children under 5 years of age died annually in 1974-1990 from
all causes other than diseases and congenital abnormalities."10
In his response to Daly and Wilson's defense, Buller falls back on
saying that his argument "was not that bias in U.S. data accounts for
overrepresentation in Canadian or other data, but that
overrepresentation in those data may be found to be an artifact of
recording if empirical research into bias, such as that of the
Colorado study, were conducted."11 However, the amount of bias
required in the Canadian data would have to be enormous.
Other lines of evidence provide additional support for the Cinderella
Effect. Victim self report studies show a higher percentage of abuse
attributed to stepparents than to genetic parents. And stepparents
themselves report that they experience less parental love toward
stepchildren than they do toward genetic children. For Buller's
critique to hold up, all of these lines of independent evidence would
have to be similarly biased. This is possible, but not probable.
The Case of the Green-Eyed Monster(s): Buller's Critique of Buss
David Buss and his colleagues have studied the Darwinian basis of
mating, conflict between the sexes, social status, homicide, and
jealousy.12 Buller concentrates his attack on jealousy.
Buss predicted that "because reproductive consequences of infertility
and partner loss for males and females are parallel in some respects,
and asymmetric in others,"13 they would be similar in some respects,
but different where evolution presented them with different problems.
They would differ because, "males risk both lowered paternity
probability and investment in rival gametes if their mates have sexual
contact with other males," while females "do not risk lowered
maternity probability through partner infidelity, but they do risk the
diversion of their mate's commitment and resources to rival
For a male, being a cad isn't so bad, but being cuckolded definitely
is. "It is a wise father who knows his own child." For a female,
however, "maternity is a certainty," so being left holding the baby by
a deadbeat dad is definitely bad, especially if his resources are
being squandered dallying with Dolly.
In their TCS response to Buller, Buss and co-author Martie Haselton
list four ways males and females were predicted to be similar, and 13
ways in which they were predicted to be different. Derived from
Darwinian theory, they have all been tested and confirmed.15
Boxes 1 and 2 in Buller's article here summarize the critical
male-female difference -- the response to sexual versus emotional
infidelity. In every case, males were more upset than females by the
sexual scenario. Buller does not question the data, only Buss's
conclusion. Confirming the evolutionary explanation requires evidence
that males become more upset about sexual infidelity than they do
about the emotional unfaithfulness.
In his TCS reply, Buss notes that he and his colleagues "were careful
to state the prediction not in terms of absolute levels of jealousy,
which are affected by many factors external to the hypothesis, but
rather in sex differences in sensitivities to different forms of
infidelity."16 Buller retorts that this is "retrofitting their
predictions to the data."17 Is it?
In 1992, Buss et al. wrote that their "central hypothesis" derived
from Darwinian theory was that both sexes should be distressed over
both sexual and emotional infidelity but that the "two kinds of
infidelity should be weighted differently by men and women."18
(Emphasis added.) In 1999, Buss emphasized the point that, "Both
sexes, of course, are distressed by both forms of infidelity, and the
evolutionary hypothesis suggests that they should be, given their
correlated nature in everyday life....The hypothesis, rather, is about
sex differences in the emotional weighting of the aspects of
infidelity."19 (Emphasis added.) Buss's original reasoning may not
satisfy Buller, but his response is hardly "retrofitting."
Buller cites a study that shows that males are more physiologically
aroused than females by sexual content generally which, he says, "Buss
himself had admitted would undermine his theory." What Buss actually
wrote is that future research "could profitably explore" their
correlation."20 And what, if not adaptation, explains the greater male
arousal? While cultural factors play some part, Buss and his
colleagues have not denied them, but documented them.21
Buller offers an alternative to the evolutionary explanation, which he
dubs "the relationship jeopardy hypothesis." It says the sex
difference is "a product of typical differences in the information
believed by the sexes, not of a sex difference in the design of the
mechanisms that process that information." This "belief hypothesis" is
based on the research of DeSteno and Salovey.22 Evolutionary
psychologists are hardly ignorant of it. The 1999 paper by Buss et
al., which Buller cites, addresses their methodological critique of
the evolutionary hypothesis and details the conceptual difficulties
with the belief hypothesis. Finally, it describes the results of four
experiments that pitted the two against each other and found "the
belief hypothesis is not well supported."23 Like the Cinderella
Effect, the sex difference in jealousy has been confirmed by other
researchers, in different countries, applying various experimental
designs and statistical methods to a number of independent datasets.
Conclusion: Cased Dismissed
In his case against Evolutionary Psychology, Buller misses -- or
skillfully avoids -- the big picture. The interesting, though by no
means novel, points he makes fit Richard Dawkins' description of
earlier such criticisms as "a catalogue of methodological shortcomings
of particular studies."24
Buller fashions his arguments like a defense attorney in a criminal
case. He attempts to sow doubt regarding this or that piece of
evidence, or to offer alternative interpretations as to what might
have happened. The scientific method, however, is like a civil case,
where the standard is not "beyond a reasonable doubt" but rather "the
preponderance of evidence." Moreover, a civil case does not require an
either-or verdict of "guilty" or "not guilty;" rather, liability can
be apportioned. Likewise, in the behavioral sciences especially, a
good theory or hypothesis need not explain everything, but only
provide the simplest and most coherent explanation.
Evolutionary psychology satisfies philosopher Imre Lakatos' criterion
that true science is "progressive." It has proven able "to `digest'
(successfully account for) apparent anomalies and generate novel
predictions and explanations" and therefore has "the hallmarks of a
currently progressive research program capable of providing us with
new knowledge of how the mind works."25 A glance at the recently
published Handbook of Evolutionary Psychology26 (edited by David Buss)
shows just how vigorous and productive the field is.
Important challenges remain, however. The most important are
determining the role of domain-specific versus domain-general
processes27 and integrating evolutionary psychology, behavior
genetics, neurosciences, and psychometrics.28
The critics notwithstanding, Evolutionary Psychology is here to stay.
2. Buller, D. J. 2005. Adapting Minds: Evolutionary Psychology and
the Persistent Quest for Human Nature. Cambridge, MA: MIT Press.
3. In addition to Buller's web site see
http://www.psych.ucsb.edu/research/cep/buller.htm for the TCS
responses by Tooby & Cosmides, Daly & Wilson, and Buss.
4. Buss, D. M. 2004. Evolutionary Psychology: The New Science of the
Mind. pp. 56-57. NY: Pearson.
5. For detailed descriptions of the original studies and citations to
them see Daly & Wilson's web page
(http://psych.mcmaster.ca/dalywilson/research.html) that also
contains their classic article, "The `Cinderella Effect': Elevated
Mistreatment of Stepchildren in Comparison of Those Living with
Genetic Parents" as well one of their replies to Buller. Another
reply by Daly & Wilson appears in the journal, Trends in Cognitive
Sciences in November 2005.
6. Daly, M. and M. I. Wilson. 1981. "Abuse and Neglect of Children in
Evolutionary Perspective." In Alexander, R. D. and D. W. Tinkle.
(Eds.). Natural Selection and Social Behavior. NY: Chiron Press,
7. Ibid. p. 408.
8. Ibid. p. 409.
9. Ibid. p. 405.
10. Daly, M. and Wilson, M. 2005. Reply to David Buller.
http://psych.mcmaster.ca/dalywilson/research.html, p. 1
11. Buller, D. J., J. Fodor, and T. Crume. 2005. "The Emperor is Still
Under-Dressed." Trends in Cognitive Science. (forthcoming), p. 2.
13. Buss, D. M. and M. Haselton. 2005. "The Evolution of Jealousy: A
Reply to Buller." Trends in Cognitive Science. November. p. 1.
14. Buss, D.M., R. J. Larsen, W. Westen, and J. Semmelroth. 1992. "Sex
Difference in Jealousy: Evolution, Physiology, and Psychology."
Psychological Science. Vol. 3 No. 4. p. 251.
15. Buss and Haselton, 2005, pp. 1-2.
16. Ibid., p. 3.
17. Buller, Fodor, and Crume, 2005, p. 1.
18. Buss et al., 1992, p. 251.
19. Buss D. M., T. K. Shackelford, L. A. Kirkpatrick, J. C. Choe, H.
K. Lim, M. Hasegawa, T. Hasegawa, and K. Bennett. 1999. "Jealousy
and the Nature of Beliefs about Infidelity: Test of competing
Hypotheses about Sex Differences in the United States, Korea, and
Japan." Personal Relationships. Vol. 6 No. 4, pp. 125-126.
20. Buss et al., 1992, p. 255.
21. Buss et al., 1999, pp. 139-146.
22. DeSteno, D. A., and P. Salovey. 1996. "Evolutionary Origins of Sex
Differences in Jealousy?" Psychological Science Vol. 7, pp.
367-372. DeSteno, D. A., and P. Salovey. 1996. "Genes, Jealousy,
and the Replication of Misspecified Models." Psychological Science
Vol. 7, pp. 376-377.
23. Buss et al., 1999, p. 148.
24. Dawkins, R. 2005. "Afterword." In Buss, D. M. The Handbook of
Evolutionary Psychology. NY: Wiley, pp. 977-978.
25. Ketellar, T., and Ellis, B. J. 2000. "Are Evolutionary
Explanations Unfalsifiable? Evolutionary Psychology and the
Lakatosian Philosophy of Science." Psychological Inquiry. Vol. 11.
No. 1. p. 2.
26. Buss, D. M. 2005. The Handbook of Evolutionary Psychology. NY:
27. Buss, D. M. 2004, pp. 56-57.
28. Bailey, J. M. 1997. "Are Genetically Based Individual Differences
Compatible With Species-Wide Adaptations?" In Segal, N. L., G. E.
Weisfeld, and C. C. Weisfeld. (Eds.) Uniting Psychology and
Biology. Washington, D.C.: American Psychological Association, pp.
81-100. Segal, N. L., and K. B. MacDonald. 1998. "Behavior
Genetics and Evolutionary Psychology: A Unified Perspective on
Personality Research." Human Biology. Vol. 70, pp. 159-184.
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