ASU Research E-Magazine: A Matter of Rape

When the subject is rape and its cause, biological theories are usually overlooked, possibly because many lawyers are uncomfortable with science.

Every new idea is met with fear. Take, for example, the recently published book outlining a new theory on the causes of rape. In A Natural History of Rape: Biological Bases of Sexual Coercion, authors Randy Thornhill and Craig T. Palmer argue that rape is an evolved behavior that led, in the past, to the increased reproductive success of some men. The idea challenges the widely accepted feminist theory that rape is about violence, not sex. Not surprisingly, the book has sparked some particularly vicious public debate.

Some of the most vehement critics of the theory, however, don’t attack the science behind it as much as they do its potential effects. Genetic defenses at trial will set rapists free, they predict. Women will be forbidden to wear miniskirts because men can’t control their biological urges. All men will be viewed as potential rapists.

Not likely, says Owen Jones, a law professor at Arizona State University. Jones studies the evolutionary theories of human behavior and how they impact the American legal system.

“This is probably one of the most volatile areas because it is so easily misunderstood. I spend a lot of time trying to clear the underbrush of major misconceptions that people have about biological theories–and there are a lot of them,” he says.

Perhaps the most common misconception is the idea of genetic determinism.

“Some people think if you’re going to talk about the biology of rape you must be about to suggest that there’s a ‘rape gene.’ And it follows that you must be about to say that those people who have it can’t be held responsible for rapes they commit. All of that is wrong,” says Jones.

“Biologists are not claiming that there is a one-to-one correspondence between having any kind of gene and exhibiting any kind of human behavior. Sound biology does not lead us to the conclusion that people are not responsible for their behaviors.”

Human behavior is far more complex than traits like eye color or blood type. Biologists studying sexual aggression aren’t looking for a “rape gene” that sets rapists apart from other people. Instead, they examine similarities between people that may have evolved to promote a certain behavior under specific environmental conditions.

For example, many people have a genetic predisposition toward depression. Certain environmental cues–such as stressful events–can trigger that depression. But not all individuals with this predisposition become depressed, even under extreme stress. Nor will all men commit rape, even under circumstances that otherwise increase the probability.

“Think of the weather as an analogy,” explains Jones. “Meteorology is not an exact science. The meteorologist doesn’t tell us how a particular cloud is going to move or what its shape will be. But the science can provide very accurate predictions about the general patterns or trends that are likely to emerge. The same thing is more or less true about the biology of human behavior. We can’t predict how any single individual is going to behave with real confidence. But…we can get a sense of what outcomes are more likely to emerge from a population numbered in the millions.”

Jones says that biology and culture work hand-in-hand. The human brain cannot develop without an environment that helps to shape it. And the environment cannot be processed without a biological superstructure, which is a product of evolution.

“Anything that has ‘nature vs. nurture’ in its title is necessarily headed in the wrong direction,” he says. “There’s a famous way of putting it that says, ‘to ask whether or not a given behavior is a function of nature or nurture is like asking whether the area of a rectangle is a product of its length or its width.’ These things cannot operate independently.”

Jones says many people fear biobehavioral theories because they assume that, in biological terms, “natural” is synonymous with “acceptable.” This simply isn’t true. Even when a behavior is an evolved trait, we do not have to condone it any more than we would condone a learned behavior.

“We’re trying to explain a phenomenon, not justify it,” says Jones. “What has happened over time is that our preferences about the way we wish the world were sometimes drives our beliefs about how the world is.”

There are two ways that rape behavior could have evolved. It could either be an evolutionary adaptation or a by-product of other adaptations. An adaptation is a heritable trait that directly contributes to an individual’s reproductive success. The trait may arise randomly through a genetic mutation. However, if it helps an individual to survive and reproduce, the trait gets passed down through the generations and spreads throughout the population.

A trait that provides a mere one percent reproductive advantage will swell from a one percent representation in the population to 99 percent in 265 generations–mere moments in evolutionary time.

An easy example of an adaptive trait is human enjoyment of sex.

“It is undoubtedly the case that sex is pleasurable compared to a lot of other activities because, on average, it tended to lead to reproductive success,” says Jones. “There aren’t likely to be many people today descended from ancestors who were disgusted by sex.”

On the other hand, adaptive behaviors don’t always increase reproductive success in today’s world, which is very different than the world in which our ancestors evolved. In fact, the past couple of generations presented massive cultural and technological changes that have rendered some evolutionary adaptations unsuccessful for reproduction.

“Sex itself is notoriously unproductive among couples who are intentionally using contraception, and yet the basic motivation to have sex remains. The fact that you may choose to have sex with somebody who will not yield a baby doesn’t mean that the sexual desire is unrelated to the historical significance of sex and babies,” Jones explains.

Unlike adaptations, evolutionary by-products do not necessarily contribute to an individual’s reproductive success. Instead, they are like a “side-effect” of other traits that are adaptive.

For example, males may have evolved to seek out many sex partners, to be able to enjoy non-committed sexual relationships, and to be physically aggressive. These traits allow men to compete with other males and mate with many women, increasing the odds that pregnancy will occur. Under certain circumstances, such as an absence of willing sex partners, these traits could conceivably lead to rape.

In such a case, rape would be a by-product of the other traits, not an adaptation itself.

These hypotheses contradict the widely accepted sociological theory of rape, which says that rape is never about sex, but about violence and control.

“[Social scientists say] it’s purely a construct of male hatred of women, a specific intent to harm and humiliate. That may very well be true in some cases,” says Jones.

He adds, however, that several motives can drive a single crime. The conscious motives that rapists cite for their actions may not be the only factors involved.

“It’s fundamentally a scientific question. It turns out that there’s a lot of data to suggest that in addition to the conscious motives that may be involved, the actual patterns of who commits rapes, who is raped, and the trauma of victims are very similar to what’s going on elsewhere in the animal kingdom. We’re playing out patterns that appear in creatures that don’t have what we think of as culture and higher consciousness.”

This data, however, has come under fire from many social scientists.

“This has to be handled with such delicacy, and also such an emphasis on what the goal is,” Jones says. “The goal is to reduce sexual aggression. Nobody’s questioning that goal. The question is, how can you use insights from various disciplines to further that goal?”

Sociological theory has furthered the goal in many ways, bringing about shield laws to protect victims and eliminating the marital rape exemption, for example. While these changes have had a positive impact, rape still plagues our society.

In addition, social science perspectives have failed to answer some important questions about rape. Why is it overwhelmingly a male behavior in every species where it is observed? Why are reproductive-aged victims highly over-represented compared to the overall population and compared to female victims of other crimes? Why does the mean age of rapists remain about 25, even though most rapists are never caught or punished?

Jones believes we need to use a more comprehensive model of human behavior to boost prevention and punishment of rape.

“Law fundamentally deals in models of human behavior,” he says. “You can think of the legal system as a lever to move behavior in a socially desirable direction. The model of human behavior is more or less the fulcrum against which the law levers. The weaker the fulcrum, the more inefficient the legal effort to change the behavior,” he says.

Current legal approaches are based primarily on sociological/feminist models. Biological theories are largely overlooked, possibly because many lawyers are uncomfortable with science.

“Most people went to law school in part because they were not drawn to sciences. Most law professionals have no background in science at all beyond high school,” Jones says.

He argues that the legal profession needs to draw on a more interdisciplinary model of human behavior.

“You cannot look just to sociology or feminism or any of the other disciplines, you have to look at their intersection and try to come up with something that looks at people as whole organisms,” he says. “There’s simply no way you can have a deep understanding of the human brain without understanding some of the evolutionary processes by which the brain was designed.”

In May 1998, Jones and ASU law professor Dan Strouse hosted a conference on biology, sexual aggression and the law. The session was sponsored by ASU’s Center for the Study of Law, Science and Technology and funded by a grant from the National Science Foundation. Randy Thornhill and Craig Palmer both presented at the workshop, along with a variety of lawyers, psychologists, criminologists, biologists, ecologists and anthropologists.

The grant also allowed Jones and his colleagues to put together a special Winter 1999 edition of Jurimetrics: The Journal of Law, Science and Technology. The publication examined the biology of rape and its effects on the legal system.

“If it turns out, for example, that sexual desire is relevant at some level to the incidence of sexual aggression, then a policy to reduce rape may be in some tension with a policy to reduce prostitution,” suggests Jones.

An Australian study conducted in the 1960s supports this notion. In the seven-year period following the closure of brothels in Queensland, the conviction rate for rape and attempted rape was triple that of the seven-year period before the closure. This increase in rapes also tripled the rate of increase in convictions for other violent crimes over the same time period.

Biological theories could also affect the debate over chemical castration. Currently, six states allow chemical treatment of sex offenders as a condition of parole, and at least 22 others have considered such legislation. If rape is purely a crime of violence, these treatments should have little effect on recidivism. If rape is due in part to sexual desire, however, then chemical castration is likely to reduce the reoccurrence of rape in treated individuals.

Jones says that some states have reclassified rape as “sexual assault,” lumping it in with other types of assault on the assumption that rape is a crime of violence. This action shows that we take rape as seriously as other violent crimes, but may make it difficult for judges to punish rapists more severely than other violent criminals. Yet women overwhelmingly report that rape is more traumatic than any other assault, even when the rape causes no bodily injury.

Researchers have also found that men and women perceive the severity of rape differently. Men often have trouble understanding why rape, above nearly all other crimes, is so traumatic for women. Some evolutionary biologists believe that women have adapted psychologically to be horrified by rape because it eliminates their choice in reproductive partners. However, men make most decisions about rape laws and sentencing. If men do not view rape to be as traumatic as women do, these laws may leave women feeling that justice has not been served.

On the other hand, acknowledging psychological differences among men and women could have negative effects. For example, it could justify gender discrimination in hiring for jobs that expose workers to rape-risky environments.

Although evolutionary approaches to rape often seem to contradict sociological approaches, Jones says we cannot understand the causes of human behavior without viewing them from all relevant disciplines.

“All behavior is necessarily a function of both our genetic potentiality and the specific environmental circumstances in which an organism is behaving,” he explains.

“I see my work as part of a larger, integrative development in which the boundaries between psychology and medicine, between philosophy and law and biology and anthropology and economics are all starting to dissolve in ways that ultimately further a more holistic understanding of where behavior comes from. That can help law do its job.”—Diane Boudreau