Rape

[Kelley]

PUBLISHED BY THE NEW YORK ACADEMY OF SCIENCES · JANUARY/FEBRUARY 2000

                                   FEATURE

                             Why Men Rape

             Prevention efforts will founder until they are based on the
understanding that rape evolved as a form of male reproductive behavior 

                    BY RANDY THORNHILL AND CRAIG T. PALMER

                                                               

                              Kiki Smith, Las Animas, 1997


                                INTRODUCTION

    A friend of ours once told us about her rape. The details hardly
matter, but in outline her story is numbingly familiar. After a movie she
returned with her date to his car, which had been left in an
isolated parking lot. She was expecting him to drive her home. Instead, the
man locked the car doors
and physically forced her to have sex with him.  

    Our friend was emotionally scarred by her experience: she became
anxious about dating, and even
about going out in public. She had trouble sleeping, eating and
concentrating on her work. Indeed,
like some war veterans, rape victims often suffer from post-traumatic
stress disorder, in which
symptoms such as anxiety, memory loss, obsessive thoughts and emotional
numbness linger after a
deeply disturbing experience. Yet gruesome ordeals like that of our friend
are all too common: in a
1992 survey of American women aged eighteen and older, 13 percent of the
respondents reported
having been the victim of at least one rape, where rape was defined as
unwelcome oral, anal or
vaginal penetration achieved through the use or threat of force. Surely,
eradicating sexual violence is
an issue that modern society should make a top priority. But first a
perplexing question must be
confronted and answered: Why do men rape? 

The quest for the answer to that question has occupied the two of u s
collectively for more than forty
years. As a purely scientific puzzle, the problem is hard enough. But it is
further roiled by strong
ideological currents. Many social theorists view rape not only as an ugly
crime but as a symptom of
an unhealthy society, in which men fear and disrespect women. In 1975 the
feminist writer Susan
Brownmiller asserted that rape is motivated not by lust but by the urge to
control and dominate. In
the twenty-five years since, Brownmiller’s view has become mainstream. All
men feel sexual desire,
the theory goes, but not all men rape. Rape is viewed as an unnatural
behavior that has nothing to do
with sex, and one that has no corollary in the animal world.  

    Undoubtedly, individual rapists may have a variety of motivations. A
man may rape because, for
instance, he wants to impress his friends by losing his virginity, or
because he wants to avenge himself
against a woman who has spurned him. But social scientists have not
convincingly demonstrated that
rapists are not at least partly motivated by sexual desire as well. Indeed,
how could a rape take place
at all without sexual motivation on the part of the rapist? Isn’t sexual
arousal of the rapist the one
common factor in all rapes, including date rapes, rapes of children, ra pes
of women under anesthetic
and even gang rapes committed by soldiers during war? 

                            CHALLENGING OLD IDEAS

    We want to challenge the dearly held idea that rape is not about sex.
We realize that our
approach and our frankness will rankle some social scientists, including
some serious and
well-intentioned rape investigators. But many facts point to the conclusion
that rape is, in its very
essence, a sexual act. Furthermore, we argue, rape has evolved over
millennia of human history,
along with courtship, sexual attraction and other behaviors related to the
production of offspring. 

Consider the following facts: 

• Most rape victims are women of childbearing age. 

• In many cultures rape is treated as a crime against the victim’s husband. 

• Rape victims suffer less emotional distress when they are subjected to
more violence. 

• Rape takes place not only among human beings but also in a variety of
other animal species. 

• Married women and women of childbearing age experience more psychological
distress after a rape than do girls, single women or women who are past
menopause. 

    As bizarre as some of those facts may seem, they all make sense when
rape is viewed as a natural, biological phenomenon that is a product of the
human evolutionary heritage. 

    Here we must hasten to emphasize that by categorizing a behavior as
"natural" and "biological" we
do not in any way mean to imply that the behavior is justified or even
inevitable. Biological means "of
or pertaining to life," so the word applies to every human feature and
behavior. But to infer from
that—as many of our critics assert that we do—that what is biological is
somehow right or good,
would be to fall into the so-called naturalistic fallacy. That mistake is
obvious enough when one
considers such natural disasters as epidemics, floods and tornadoes. In
those cases it is clear that
what is natural is not always desirable. And of course much can be, and is,
done to protect people
against natural threats—from administering antibiotics to drawing up
emergency evacuation plans. In
other words, the fact that rape is an ancient part of human nature in no
way excuses the rapist 

                           RAPE: NATURE VS. NATURE

    Why, then, have the editors of scholarly journals refused to publish
papers that treat rape from
a Darwinian perspective? Why have pickets and audience protesters caused
public lectures on the
evolutionary basis of rape to be canceled or terminated? Why have
investigators working to discover
the evolutionary causes of rape been denied positions at universities?  

    The reason is the deep schism between many social scientists and
investigators such as ourselves
who are proponents of what is variously called sociobiology or evolutionary
psychology. Social
scientists regard culture— everything from eating habits to language—as an
entirely human invention,
one that develops arbitrarily. According to that view, the desires of men
and women are learned
behaviors. Rape takes place only when men learn to rape, and it can be
eradicated simply by
substituting new lessons. Sociobiologists, by contrast, emphasize that
learned behavior, and indeed all culture, is the result of psychological
adaptations that have evolved over long periods of time. Those adaptations,
like all traits of individual human beings, have both genetic and
environmental
components. We fervently believe that, just as the leopard’s spots and the
giraffe’s elongated neck
are the result of aeons of past Darwinian selection, so also is rape.  

    That conclusion has profound and immediate practical consequences. The
rape-prevention
measures that are being taught to police officers, lawyers, parents,
college students and potential
rapists are based on the prevailing social-science view, and are therefore
doomed to fail. The
Darwinian theory of evolution by natural selection is the most powerful
scientific theory that applies to
living things. As long as efforts to prevent rape remain uninformed by that
theory, they will continue to
be handicapped by ideas about human nature that are fundamentally
inadequate. We believe that only by acknowledging the evolutionary roots of
rape can prevention tactics be devised that really work.  

                             GENDER DIFFERENCES

    From a Darwinian perspective, every kind of animal—whether grasshopper
or gorilla, German
or Ghanaian—has evolved to produce healthy children that will survive to
pass along their parents’
genetic legacy. The mechanics of the phenomenon are simple: animals born
without traits that led to
reproduction died out, whereas the ones that reproduced the most succeeded
in conveying their
genes to posterity. Crudely speaking, sex feels good because over
evolutionary time the animals that
liked having sex created more offspring than the animals that didn’t. 

    As everyone knows all too well, however, sex and the social behaviors
that go with it are endlessly complicated. Their mysterious and tangled
permutations have inspired flights of literary genius throughout the ages,
from Oedipus Rex to Portnoy’s Complaint. And a quick perusal of the
personal-growth section of any bookstore—past such titles as Men Are from
Mars, Women Are
from Venus and You Just Don’t Understand—is enough to show that one reason
sex is so
complicated is that men and women perceive it so differently. Is that the
case only because boys and
girls receive different messages during their upbringing? Or, as we
believe, do those differences
between the sexes go deeper? 

    Over vast periods of evolutionary time, men and women have confronted
quite different
reproductive challenges. Whereas fathers can share the responsibilities of
child rearing, they do not
have to. Like most of their male counterparts in the rest of the animal
kingdom, human males can
reproduce successfully with a minimal expenditure of time and energy ; once
the brief act of sexual
intercourse is completed, their contribution can cease. By contrast, the
minimum effort required for a
woman to reproduce successfully includes nine months of pregnancy and a
painful childbirth.
Typically, ancestral females also had to devote themselves to prolonged
breast-feeding and many
years of child care if they were to ensure the survival of their genes. In
short, a man can have many
children, with little inconvenience to himself; a woman can have only a
few, and with great effort. 

    That difference is the key to understanding the origins of certain
important adaptations—features
that persist because they were favored by natural selection in the past.
Given the low cost in time and
energy that mating entails for the male, selection favored males who mated
frequently. By contrast,
selection favored females who gave careful consideration to their choice of
a mate; that way, the high
costs of mating for the female would be undertaken under circumstances that
were most likely to
produce healthy offspring. The result is that men show greater interest
than women do in having a
variety of sexual partners and in having casual sex without investment or
commitment. That
commonplace observation has been confirmed by many empirical studies. The
evolutionary
psychologist David M. Buss of the University of Texas at Austin, for
instance, has found that women
around the world use wealth, status and earning potential as major criteria
in selecting a mate, and
that they value those attributes in mates more than men do. 

    Remember, none of the foregoing behavioral manifestations of evolution
need be conscious.
People do not necessarily have sex because they want children, and they
certainly do not conduct
thorough cost-benefit analyses before taking a partner to bed. As Darwin
made clear, individual
organisms merely serve as the instruments of evolution. Men today find
young women attractive
because during human evolutionary history the males who preferred
prepubescent girls or women too
old to conceive were outreproduced by the males who were drawn to females
of high reproductive
potential. And women today prefer successful men because the females who
passed on the most
genes, and thereby became our ancestors, were the ones who carefully
selected partners who could
best support their offspring. That is why, as the anthropologist Donald
Symons of the University of
California, Santa Barbara, has observed, people everywhere understand sex
as "something females
have that males want."  

                               THE MATING GAME

    A dozen roses, romantic dinners by candlelight, a Tiffany engagement
ring: the classic
courtship ritual requires lots of time, energy and careful attention to
detail. But people are far from
unique in that regard: the males of most animal species spend much of their
energies attracting,
wooing and securing sexual partners. The male woodcock, for instance,
performs a dramatic display
each spring at mating time, soaring high into the air and then tumbling to
the ground. Male fireflies are
even flashier, blinking like neon signs. The male bowerbird builds a
veritable honeymoon cottage: an
intricate, sculpted nest that he decorates with flowers and other colorful
bric-a-brac. Male deer and
antelope lock antlers in a display of brute strength to compete for females.  

    Once a female’s interest is piqued, the male behaves in various ways to
make her more sexually
receptive. Depending on the species, he dances, fans his feathers or offers
gifts of food. In the
nursery web spider, the food gift is an attempt to distract the female, who
otherwise might literally
devour her partner during the sex act. The common thread that binds nearly
all animal species seems
to be that males are willing to abandon all sense and decorum, even to risk
their lives, in the frantic
quest for sex. 

    But though most male animals expend a great deal of time and energy
enticing females, forced
copulation—rape—also occurs, at least occasionally, in a variety of
insects, birds, fishes, reptiles,
amphibians, marine mammals and nonhuman primates. In some animal species,
moreover, rape is
commonplace. In many scorpionfly species, for instance—insects that one of
us (Thornhill) has
studied in depth—males have two well-formulated strategies for mating.
Either they offer the female a nuptial gift (a mass of hardened saliva they
have produced, or a dead insect) or they chase a female
and take her by force. 

    A remarkable feature of these scorpionflies is an appendage that seems
specially designed for
rape. Called the notal organ, it is a clamp on the top of the male’s
abdomen with which he can grab
on to one of the female’s forewings during mating, to prevent her escape.
Besides rape, the notal
organ does not appear to have any other function. For example, when the
notal organs of males are
experimentally covered with beeswax, to keep them from functioning, the
males cannot rape. Such
males still mate successfully, however, when they are allowed to present
nuptial gifts to females. And
other experiments have shown that the notal organ is not an adaptation for
transferring sperm: in
unforced mating, the organ contributes nothing to insemination. 

    Not surprisingly, females prefer voluntary mating to mating by force:
they will approach a male
bearing a nuptial gift and flee a male that does not have one.
Intriguingly, however, the males, too,
seem to prefer a consensual arrangement: they rape only when they cannot
obtain a nuptial gift.
Experiments have shown that when male scorpionflies possessing nuptial
gifts are removed from an
area, giftless males—typically, the wimpier ones that had failed in
male-male competitions over
prey—quickly shift from attempting rape to guarding a gift that has been
left untended. That
preference for consensual sex makes sense in evolutionary terms, because
when females are willing,
males are much more likely to achieve penetration and sperm transfer. 

    Human males obviously have no external organ specifically designed for
rape. One must therefore
look to the male psyche—to a potential mental rape organ—to discover any
special-purpose
adaptation of the human male to rape. 

                        RAPE AS REPRODUCTIVE STRATEGY

    Since women are choosy, men have been selected for finding a way to be
chosen. One way to
do that is to possess traits that women prefer: men with symmetrical body
features are attractive to
women, presumably because such features are a sign of health. A second way
that men can gain
access to women is by defeating other men in fights or other kinds of
competitions—thereby gaining
power, resources and social status, other qualities that women find
attractive. 

    Rape can be understood as a third kind of sexual strategy: one more way
to gain access to 
females. There are several mechanisms by which such a strategy could
function. For example, men
might resort to rape when they are socially disenfranchised, and thus
unable to gain access to women
through looks, wealth or status. Alternatively, men could have evolved to
practice rape when the
costs seem low—when, for instance, a woman is alone and unprotected (and
thus retaliation seems
unlikely), or when they have physical control over a woman (and so cannot
be injured by her). Over
evolutionary time, some men may have succeeded in passing on their genes
through rape, thus
perpetuating the behavior. It is also possible, however, that rape evolved
not as a reproductive
strategy in itself but merely as a side effect of other adaptations, such
as the strong male sex drive and the male desire to mate with a variety of
women. 

    Take, for instance, the fact that men are able to maintain sexual
arousal and copulate with unwilling
women. That ability invites inquiry, according to the psychologist Margo
Wilson of McMaster
University in Hamilton, Ontario, and her coworkers, because it is not a
trait that is common to the
males of all animal species. Its existence in human males could signal that
they have evolved
psychological mechanisms that specifically enable them to engage in forced
copulation—in short, it
could be a rape adaptation. But that is not the only plausible explanation.
 The psychologist Neil M.
Malamuth of the University of California, Los Angeles, points out that the
ability to copulate with
unwilling women may be simply a by-product of men’s "greater capacity for
impersonal sex." 

                          IS RAPE AN ACT OF VIOLENCE?

    More research is needed to decide the question of whether rape is an
adaptation or merely a
by-product of other sexual adaptations. Both hypotheses are plausible: one
of us (Thornhill) supports
the former, whereas the other (Palmer) endorses the latter. Regardless of
which hypothesis prevails,
however, there is no doubt that rape has evolutionary—and thus
genetic—origins. All traits and
behaviors stem from a complex interplay between genes and the environment.
If rape is an
adaptation, men must possess genes that exist specifically because rape
increased reproductive
success. If rape turns out to be merely a side effect of other adaptations,
then the genes involved exist for reasons that have nothing to do with
rape. Either way, however, the evolutionary perspective explains a number
of otherwise puzzling facts about the persistence of rape among human males.  

    For example, if rape is evolutionary in origin, it should be a threat
mostly to women of childbearing
age. And, in fact, young adult women are vastly overrepresented among rape
victims in the female
population as a whole, and female children and post-reproductive-age women
are greatly
underrepresented.  

    By the same token, if rape has persisted in the human population
through the action of sexual
selection, rapists should not seriously injure their victims—the rapist’s
reproductive success would be
hampered, after all, if he killed his victim or inflicted so much harm that
the potential pregnancy was
compromised. Once again, the evolutionary logic seems to predict reality.
Rapists seldom engage in
gratuitous violence; instead, they usually limit themselves to the force
required to subdue or control
their victims. A survey by one of us (Palmer), of volunteers at rape crisis
centers, found that only 15
percent of the victims whom the volunteers had encountered reported having
been beaten in excess
of what was needed to accomplish the rape. And in a 1979 study of 1,401
rape victims, a team led
by the sociologist Thomas W. McCahill found that most of the victims
reported being pushed or held, but that acts of gratuitous violence, such
as beating, slapping or choking, were reported in only a minority of the
rapes—22 percent or less. A very small number of rape victims are murdered:
about .01 percent (that figure includes unreported as well as reported
rapes). Even in those few cases, it may be that the murder takes place not
because the rapist is motivated by a desire to kill, but because by
removing the only witness to the crime he greatly increases his chance of
escaping
punishment. 

                             PSYCHOLOGICAL PAIN

    Rape is more distressing for women than are other violent crimes, and
evolutionary theory can
help explain that as well. In recent years research on human unhappiness
informed by evolutionary
theory has developed substantial evidence about the functional role of
psychological pain. Such pain
is thought to be an adaptation that helps people guard against
circumstances that reduce their
reproductive success; it does so by spurring behavioral changes aimed at
preventing future pain [see
"What Good Is Feeling Bad?" by Randolph M. Nesse, November/December 1991]
Thus one would expect the greatest psychological pain to be associated with
events that lower one’s reproductive success, and, indeed, emotionally
traumatic events such as the death of a relative, the
loss of social status, desertion by one’s mate and the trauma of being
raped can all be interpreted as
having that effect.  

    Rape reduces female reproductive success in several ways. For one
thing, the victim may be
injured. Moreover, if she becomes pregnant, she is deprived of her chance
to choose the best father
for her children. A rape may also cause a woman to lose the investment of
her long-term partner,
because it calls into question whether the child she later bears is really
his. A variety of studies have
shown that both men and women care more for their genetic offspring than
for stepchildren. 

    One of us (Thornhill), in association with the anthropologist Nancy W.
Thornhill, has conducted a
series of studies on the factors that contribute to the emotional pain that
women experience after a
rape. Those studies confirmed that the more the rape interfered with the
women’s reproductive
interests, the more pain they felt. The data, obtained from the Joseph J.
Peters Institute in
Philadelphia, came from interviews with 790 girls and women who had
reported a sexual assault and
who were subsequently examined at Philadelphia General Hospital between
1973 and 1975. The
subjects, who ranged in age from two months to eighty-eight years, were
asked a variety of questions designed to evaluate their psychological
responses to the rape. Among other
things, they were asked about changes in their sleeping habits, in their
feelings toward known and
unknown men, in their sexual relations with their partners (children were
not asked about sexual
matters), and in their eating habits and social activities. 

    Analysis of the data showed that young women suffered greater distress
after a rape than did
children or women who were past reproductive age. That finding makes
evolutionary sense, because
it is young women who were at risk of being impregnated by an undesirable
mate. Married women,
moreover, were more traumatized than unmarried women, and they were more
likely to feel that their
future had been harmed by the rape. That, too, makes evolutionary sense,
because the doubt a rape
sows about paternity can lead a long-term mate to withdraw his support.  

    Among the women in the study, psychological pain rose inversely to the
violence of the attack. In
other words, when the rapist exerted less force, the victim was more upset
afterward. Those findings,
surprising at first, make sense in the evolutionary context: a victim who
exhibits physical evidence that
sexual access was forced may have less difficulty convincing her husband or
boyfriend that what took
place was rape rather than consensual sex. In evolutionary terms, such
evidence would be reassuring
to a pair-bonded male, because rape is a one-time event, whereas consensual
sex with other partners is likely to be frequent, and thus more threatening
to paternity. 

    Finally, women of reproductive age reported more emotional distress
when the assault involved
sexual intercourse than when it involved other kinds of sexual behavior.
Among young girls and older
women, however, penile-vaginal intercourse was no more upsetting than other
kinds of assaults.
Again, the possibility of an unwanted pregnancy may be a key factor in the
degree of trauma the
victim experiences. 

    For all those reasons, the psychological pain that rape victims suffer
appears to be an evolved
defense against rape. The human females who outreproduced others—and thus
became our
ancestors—were people who were highly distressed about rape. Their distress
presumably served
their interests by motivating them to identify the circumstances that
resulted in the rape, assess the
problems the rape caused, and act to avoid rapes in the future.  

                            IS RAPE AN ACT OF SEX?

    If women today are to protect themselves from rape, and men are to
desist from it, people must
be given advice that is based on knowledge. Insisting that rape is not
about sex misinforms both men
and women about the motivations behind rape—a dangerous error that not only
hinders prevention
efforts but may actually increase the incidence of rape.  

    What we envision is an evolutionarily informed program for young men
that teaches them to
restrain their sexual behavior. Completion of such a course might be
required, say, before a young
man is granted a driver’s license. The program might start by inducing the
young men to acknowledge the power of their sexual impulses, and then
explaining why human males have evolved in that way.  The young men should
learn that past Darwinian selection is the reason that
a man can get an erection just by looking at a photo of a naked woman, why
he may be tempted to
demand sex even if he knows that his date truly doesn’t want it, and why he
may mistake a woman’s
friendly comment or tight blouse as an invitation to sex. Most of all, the
program should stress that a man’s evolved sexual desires offer him no
excuse whatsoever for raping a woman, and that if he
understands and resist s those desires, he may be able to prevent their
manifestation in sexually
coercive behavior. The criminal penalties for rape should also be discussed
in detail. 

    Young women also need a new kind of education. For example, in today’s
rape-prevention
handbooks, women are often told that sexual attractiveness does not
influence rapists. That is
emphatically not true. Because a woman is considered most attractive when
her fertility is at its peak,
from her mid-teens through her twenties, tactics that focus on protecting
women in those age groups
will be most effective in reducing the overall frequency of rape.  

    Young women should be informed that, during the evolution of human
sexuality, the existence of
female choice has favored men who are quickly aroused by signals of a
female’s willingness to grant
sexual access. Furthermore, women need to realize that, because selection
favored males who had
many mates, men tend to read signals of acceptance into a woman’s action s
even when no such
signals are intended. 

                           COMPROMISING POSITIONS

    In spite of protestations to the contrary, women should also be advised
that the way they
dress can put them at risk. In the past, most discussions of female
appearance in the context of rape
have, entirely unfairly, asserted that a victim’s dress and behavior should
affect the degree of
punishment meted out to the rapist: thus if the victim was dressed
provocatively, she "had it coming to
her"—and the rapist would get off lightly. But current attempts to avoid
blaming the victim have led to
false propaganda that dress and behavior have little or no influence on a
woman’s chances of being
raped. As a consequence, important knowledge about how to avoid dangerous
circumstances is
often suppressed. Sure-ly the point that no woman’s behavior gives a man
the right to rape her can
be made with-out encouraging women to overlook the role they themselves may
be playing in
compromising their safety. 

    Until relatively recently in Europe and the United States, strict
social taboos kept young men and
women from spending unsupervised time together, and in many other countries
young women are still
kept cloistered away from men. Such physical barriers are understandably
abhorrent to many people, since they greatly limit the freedom of women.
But the toppling of those barriers in modern Western countries raises
problems of its own. The common practice of unsupervised dating in cars and
private homes, which is often accompanied by the consumption of alcohol,
has placed young women in environments that are conducive to rape to an
extent that is probably unparalleled in history. After studying the data on
the risk factors for rape, the sex investigators Elizabeth R. Allgeier and
Albert R. Allgeier, both of Bowling Green State University in Ohio,
recommended that men and women interact only in public places during the
early stages of their relationships—or, at least, that women exert more
control than they generally do over the circumstances in which they consent
to be alone with men. 

                          EVOLUTIONARY COUNSELING

    An evolutionary perspective on rape might not only help prevent rapes
but also lead to more
effective counseling for rape victims. A therapy program explaining that
men rape because they
collectively want to dominate women will not help a victim understand why
her attacker appeared to
be sexually motivated, why she can no longer concentrate enough to conduct
her life effectively, or
why her husband or boyfriend may view the attack as an instance of
infidelity. In addition, men who
are made aware of the evolutionary reasons for their suspicions abou t
their wives’ or girlfriends’
claims of rape should be in a better position to change their reactions to
such claims. 

    Unlike many other contentious social issues, such as abortion and
homosexual rights, everyone has
the same goal regarding rape: to end it. Evolutionary biology provides
clear information that society
can use to achieve that goal. Social science, by contrast, promotes
erroneous solutions, because it
fails to recognize that Darwinian selection has shaped not only human
bodies but human psychology,
learning patterns and behavior as well. The fact is that men, relative to
women, are more aggressive,
sexually assertive and eager to copulate, and less discriminating about
mates—traits that contribute to
the existence of rape. When social scientists mistakenly assert that
socialization alone causes those
gender differences, they ignore the fact that the same differences also
exist in all the other animal
species in which males offer less parental investment than females and
compete for access to females.

    In addressing the question of rape, the choice between the politically
constructed answers of social
science and the evidentiary answers of evolutionary biology is essentially
a choice between ideology
and knowledge. As scientists who would like to see rape eradicated from
human life, we sincerely
hope that truth will prevail. •  

                                 THE AUTHORS

Randy Thornhill isan evolutionary biologist at the University of New Mexico
in Albuquerque. Craig T. Palmer
is an evolutionary anthropologist at the University of Colorado at Colorado
Springs. This article was adapted
from their forthcoming book, A Natural History of Rape: Biological Bases of
Sexual Coercion, which is being
published in April by MIT Press.