Randy Thornhill believes in science with unrestrained enthusiasm. As a biologist and high-ranking professor at the University of New Mexico, he has devoted his 32-year career to it, and he is convinced that science can solve any problem, untangle all knots, lift any cloud.

Recently he turned his attention to an issue as old as time: rape. "If you've got a social problem, science is the only thing that can give us the answer," he says.

The answer science gave him and co-author Craig T. Palmer, a University of Colorado anthropologist, is that men rape women because evolution has programmed them to do it. Rape is a "natural" and "biological" phenomenon, "along with courtship, sexual attraction and other behaviors related to the production of offspring," they write in the current edition of the The Sciences, an academic journal.

The article is titled "Why Men Rape" and is subtitled "Prevention efforts will founder until they are based on the understanding that rape evolved as a form of male reproductive behavior." It is excerpted from their forthcoming book "A Natural History of Rape: Biological Bases of Sexual Coercion," dedicated to the "women and girls" in their lives.

Predictably, their work has prompted controversy--and not just from the "rabid women's studies people" Thornhill said picketed one of his lectures on the subject and tried to cancel another. For the last week Thornhill has been deluged with media attention, and MIT Press has alertly decided to move up the original April publication date and get the book to stores by Feb. 1 instead. Behavioral experts of all kinds and political stripes have been probed for reaction, calling the theory everything from irrelevant piffle to groundbreaking. "It makes me sick," said one scientist who did not want to be identified. "Brilliant," said another.

"We're looking to raise the public discussion of rape to a higher plane," Thornhill says, meaning "scientifically informed."

It is difficult, of course, to convince a lot of non-scientists that the words "natural" and "rape" have any business appearing in the same sentence, even if they know Thornhill and Palmer are using the words in a scientific context--meaning simply that something occurs in nature--and even though the authors jump through linguistic hoops to explain that they don't mean "the behavior is justified or even inevitable." Nor is their theory particularly new--similar ideas have been advanced since at least 1983--but Thornhill and Palmer decided to kick it into high gear.

Attitudes about rape have changed dramatically over the eons. At one time it was considered a crime against the victim's husband or father, not the woman herself. In the post-Freudian age, rapists were thought to be mentally ill, compulsive sex fiends, not criminals, and women were told to "lie back and enjoy it." It wasn't until feminists began writing on the subject (most notably Susan Brownmiller, author of the seminal "Against Our Will: Men, Women and Rape," published in 1975) that the legal system stopped requiring the victim to prove she had not consented, and began to shield her past as irrelevant to the crime at hand.

Now, at a time when taking women by force and exalting pulchritude are major themes in popular culture, it is the fear that victims will again be blamed for causing rape, just by being biologically present--or that rapists will somehow be excused by a Darwinian imperative--that is causing the uproar. Rape was not a sexual crime, Brownmiller and others argued, but an act of aggression that served to intimidate all women.

Much of this long-running debate sounds like another skirmish in the war between sociobiologists (It's evolution, of course!) and social scientists (No! It's conditioning!). The layperson is left on the sidelines wondering what this means to the estimated 1 million women, men and children every year who are forced to copulate, penetrated with foreign objects, assaulted anally and orally, or suffer from attempts to do so.

For all his love of the precision of science, Thornhill, 55, is hard put to describe how his and his co-author's theory could be used to prevent rape, other than to suggest that every male should complete a program that teaches him, in order to get a driver's license, to "restrain his sexual behavior." Women would be taught how to reduce their risk by not wearing "provocative clothing" and avoiding situations like drunken fraternity parties.

And yet Thornhill is quite, quite certain that he has the answer to why men rape, that it has little to do with all the theories about domination and power, and that this scientific knowledge could help prevent the crime.

Look to the Scorpion Fly

Science is so elegant, so uncluttered by emotion and politics. But people are so messy.

The underpinning of the Thornhill-Palmer thesis goes back to the evolutionist-biologist interpretation of human sexuality that says men ensure the continuation of the species by impregnating as many women as possible, thus being promiscuous, less emotionally involved in sex, and inclined to take it by force if they can't get it with charm. Women, given their childbearing realities, have a greater stake in being choosy about selecting a mate, particularly one who has a good job hunting and gathering.

If you buy into all this, it then follows that, historically, rape is "an adaptive reproductive strategy." They are not saying that spreading the seed is what drives men to rape today--just that that is how rape was invented in the olden days.

They cite a variety of evidence. For one, that rape occurs in other species. Three million of 25 million animal species have been studied, Thornhill says, and rape occurs in most. He cites in particular the scorpion fly, which he has studied. Generally, the male tries to mate by offering the female a "nuptial gift" of hardened saliva or a nice dead insect. But when he can't acquire such loot, he rapes. He even has a special body part--the notal organ--to clamp the female to him. This organ has no other purpose than forced copulation.

"Human males obviously have no external organ specifically designed for rape," the two scientists write. "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."

They add: "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."

They see other validation of the reproductive strategy in statistics and studies that show women of childbearing years have a higher rate of being raped than either girls under 12 or post-menopausal women, that these women are more traumatized by the rape, and that a minority of rape victims are subjected to more violence than is necessary to complete the rape. In other words, rape is more about sex than it is about domination.

This is where the political element of the controversy comes in. Thornhill says the theory that rapists prey on women out of a pathological desire to control them became popular largely "because it was thought to be a good political position in the feminist movement."

In particular, he cites Brownmiller's book, which has had enormous influence in changing the old attitudes that blamed the victim rather than the rapist. (Although not completely, as a Montgomery County judge named Durke G. Thompson proved recently when he said an 11-year-old girl was partly to blame for having been molested by a 23-year-old man.)

"Our argument is simply that the theory behind her program is scientifically bankrupt," Thornhill says.

Furthermore, he says, the feminist hold on social-science theory has created a climate in which his work, and that of others advocating Darwinian perspectives, has been suppressed. "Why have pickets and audience protesters caused public lectures on the evolutionary basis of rape to be canceled or terminated?" he and Palmer write. "Why have investigators working to discover the evolutionary causes of rape been denied positions at universities?"

Asked for specifics, he says "rabid women's studies" advocates organized to protest a lecture at a college he would not name, forcing him to speak in a basement hall to an invited audience rather than in a lecture hall for a general audience. And placard-bearing women barred his entrance to a hall at Simon Fraser University in British Columbia, then interrupted him (and his former wife and collaborator, Nancy Thornhill) with loud catcalls.

Charles Crawford, the professor of evolutionary psychology who sponsored the lecture, confirmed that the incident happened--at least 10 years ago.

A Lecture at DMV

"I never said it didn't have to do with sex," Brownmiller says. She has been out promoting her latest book, "In Our Time: Memoir of a Revolution." Her robust voice crackles with indignation over the phone. "Thornhill gives sociobiology a bad name. . . . Rape is a crime of violence that has mostly to do with young male aggression and also with cultural attitudes that kind of indicate to young men that it is a macho act to force yourself on women.

"The scorpion fly? I mean, he doesn't have much in the way of examples besides a couple of ducks and an orangutan or two. . . . Let's stick with the chimpanzees or the bonobo monkeys--they are so peaceful."

Several experts contacted over the past week have questioned the reproductive-strategy theory by pointing out that considerable numbers of rape victims are not obviously impregnable--children and post-menopausal women, men, Muslim women draped in garments that reveal nothing of either beauty or age--why are they raped? And how does he explain the large numbers of rapists who fail to ejaculate, or those who have a regular sexual partner? Thornhill says these examples are "incidental, functionally." That men will have intercourse with animals, blow-up dolls--or infertile females or men--is merely a byproduct of their indiscriminate sex drive.

Denise Snyder, executive director of the D.C. Rape Crisis Center, says the idea that women of childbearing age experience more trauma than those who are not does not correspond with her 11 years of counseling victims. "Of course, the potential of pregnancy will add a layer of concern. But a 75-year-old could have been assaulted in a way the AIDS virus could have been transmitted, so that trauma is there."

She also says the fact that comparatively few victims suffer injuries beyond the rape itself does not mean it is not a crime of aggression.

"Rape is not about the same type of aggression as a fistfight," says Snyder. "It's about domination over another person. Rape is a far more effective way to leave a person disempowered than beating somebody."

On the other hand, one psychiatrist says neither theory is significant to the question of how to prevent rape. "The argument over whether it's a misogynistic expression of power or sexual release is not important," says Sally Satel of the conservative Ethics and Public Policy Institute. "It's both, and in degrees depending on situation."

One thing nearly everyone dismisses, however, is Thornhill's idea that a lecture tied to getting your driver's license would help prevent rape.

"It borders on the absurd," says Satel. "First off, by approaching this as 'psycho education'--like teaching bipolar people they have an imbalance--they are estranging the recipients of this message from the event, making it more sterile."

Lionel Tiger, the anthropologist and author of last year's "The Decline of Males," agrees with Thornhill and Palmer on the basics, but he, too, thinks their license proposal is pointless. "Given the experience most of us have had at the motor vehicles bureau, this would be a disaster . . . ."

Thornhill and Palmer's license lesson would teach young women that "because selection favored males who had many mates, men tend to read signals of acceptance into a woman's actions even when no such signals are intended."

Jonathan Stillerman, co-executive director of the Men's Rape Prevention Project in Washington and a clinical psychologist, said he is not opposed to linking a rape prevention course to getting a driver's license, but fears that Thornhill's message is the wrong thing to teach. The article "comes dangerously close to blaming women for being sexually assaulted, and disempowering and demeaning men by suggesting we are sort of helpless in the face of our biological destiny. . . . More than likely men will come out of it with another reason to justify forcing themselves on someone because their ancestors did it."

"What about the men who don't drive?" asked Brownmiller.

Legal Presuppositions

Thornhill and Palmer want nothing less than to change the culture of thinking about rape. And, as much as they decry the politicization of rape theory, it is clear that what they want to supplant are the "Brownmillerites," as Thornhill called them.

But what is at risk here? They do not advocate going back to blaming women, or lessening criminal penalties, or viewing rape less seriously. Nor are accused rapists likely to use a Darwin-made-me-do-it defenses.

"Only someone ignorant would think this would afford a rapist a genetic defense," said Owen Jones, a law professor at Arizona State University who specializes in the legal implications of human biology, and admires Thornhill and Palmer's work.

Crawford, the Canadian professor who has also written on the subject, envisions that the definition of rape would change somewhat, depending on whether it was a "date" or acquaintance rape or a stranger-who-drags-you-behind-the-bushes rape. Standards of proof would be tougher in the former.

Jones thinks the book could change attitudes about training, and about deterrence. For example, if you think rape is about sex, you are more likely to believe that chemical castration as a term of parole would be effective, he said. If you think it's about dominance, you'd be more likely to think "chemical castration would have no effect because he could just use a hammer instead of a penis."

Jones contends that the 1994 Violence Against Women Act would be in for a major overhaul if Thornhill and Palmer's theories become mainstream. "[It] is built on a presupposition that crimes of violence against women are essentially hate crimes in the same way cross-racial crimes are hate crimes," Jones said. "If that presumption is wrong, then the efforts to use the mechanism of law to prevent rape will be less effective than everyone wants them to be. . . . There is an incredible amount of money designated in the VAWA for teaching prosecutors, etc., about the 'real' causes of rape. This is Congress adopting a single view about the causes of rape and devoting federal funds to spreading that idea, which may be fundamentally flawed."

But until someone designs an actual program or proposes an actual change in the law, the reproductive-strategy theory of rape will be just another academic firestorm. Interesting--yes, plausible--possibly, but behavior-changing? Doubtful.

"I have been working in this field for 15 years and I would lay my life on the line that the vast majority of the women I have worked with across the country would turn themselves into pumpkins if it meant we could reduce sexual violence," said Denise Snyder. "I don't care who would come up with whatever ideas--if there was something out there--it would happen in the snap of a finger."