CHARLOTTESVILLE -- In the classroom and in his new book, Steven E. Rhoads is teaching the unorthodox.

The longtime University of Virginia professor is teaching, in fact, against at least 30 years of dominant, post-sexual revolution ideology.

The women's movement has ignored the biological difference between men and women in its push for equality, he says in the book, "Taking Sex Differences Seriously." Ignoring those deep biological differences has harmed women, pushing them into the workplace to the detriment of their children, he says.

Rhoads contends, based on 10 years of research examining numerous biological and sociological studies, that most women want most of all a loving husband and children. They are happiest at home with their babies, he says.

"In the future we will see fewer women attempting to do career and family simultaneously and more who think in terms of sequencing the two," the political scientist said in an interview. "We already see evidence that increasing proportions of mothers are staying home with their newborns in the first years."

The sexual revolution has also hurt women, he said. Most women -- unlike most men -- are harmed by casual sex, he said.

"There is a nonreligious argument for women to be more chaste," he said. "It's for their self-interest. More is at stake for women."

His views have thrust him into the limelight with appearances on NBC's "Today" show and C-SPAN, and with requests for dozens of interviews from radio and newspapers across the country. His book is being used as a textbook in 60 colleges across the country. The first printing of 8,000 books sold out.

Last month, Harvard University President Lawrence H. Summers raised a furor after a speech in which he suggested that innate differences between the sexes could explain why fewer women succeed in science and math careers. Summers, in defending his remarks later, said people "would prefer to believe" that the differences in performance between sexes are due to social factors, "but these are things that need to be studied."

Rhoads agrees with Summers, noting that though women are better at math calculation, men "by their nature" are better at math reasoning or higher math -- why most astronomers and physicists are men, he says.

Critics, including some of Rhoads' own students, disagree with his assessment of women.

"Whenever anybody says women are like this and men are like that, it makes me leery," said Lisa Eorio, who has a doctorate in sociology from U.Va., where she researched gender differences. She has also debated Rhoads on gender issues.

"I don't think anything is that clear-cut," she said. "Even when there are biological differences, that doesn't easily equate into behaviors."

Ann Lane, U.Va. history professor and a former director of its Studies in Women and Gender program, said Rhoads' claims "are so old."

"They go back to the Egyptians, maybe even to the caveman. . . . There are biological differences between men and women, but we don't know what they are. . . . We are a combination of culture and biology."

"I don't think the women's movement has harmed women," said Blair Cantfil, a fourth-year student from Alexandria taking Rhoads' class. "I do think the women's movement has overestimated how much women want casual sex, but the movement hasn't prevented women from staying at home if they want to."

But Rhoads said numerous scientific studies, some done over decades, as well as his own 2002 national survey of how college faculty handle child care, reveal a much different picture than that propounded by the women's movement and feminists in general. He studied 184 assistant tenure-track professors in paid-leave programs who had children younger than 2.

The differences between men and women in sexual and interpersonal relationships, in child care, in life interests and in the pursuit of happiness can be explained at least in part by evolution -- the need to pass on one's genes, by hormones, by testosterone and other physiological and chemical distinctions, he said. Cultural pressure and even an androgynous upbringing can't change the basic biological facts, he said.

"I can't imagine that the feminist movement will look the same in 20 years," said Rhoads, 65, who joined the U.Va. faculty 35 years ago. The tenured professor is the author of three other books, including one on economics and gender. He is married with three grown sons.

In his book on sex differences, published in May by Encounter Books of San Francisco, he concluded:

• There is a distinct preference by women for cooperation over competition beginning at puberty when estrogen levels soar.
• Most women, taught by the sexual revolution that their sexual urges are identical to men's, are unsatisfied with casual sex, unlike most men.
• More women find happiness in children than in their jobs.
• Marriage makes women happier than unmarried women and is a social necessity because it makes men grow up.

On child care, for example, Rhoads said: "Women are the equal of men at lawyering and doctoring, but they are better than men at the nurturing of children. This superiority is, in large part, biologically based. . . . The hormone oxytocin promotes nurturing and bonding, and women have more neural receptors for oxytocin than men do and pregnancy gives them still more."

His study found that it is critical that one parent stay at home with the children. "Two-career families who put children in subsidized day care apparently produce a near tripling of the odds that these children will be disobedient and aggressive," he said.

Studies show that sexual differences are apparent as early as age 2, Rhoads said, and that in preschool years, girls are interested in dance and boys in balls and trucks.

A 1997 Pew Research Center survey of women found that 93 percent of mothers regard their children as a source of happiness all or most of the time, but only 60 percent of women find their careers a source of happiness all or most of the time, Rhoads said in his book.

Marriage trends have also hurt women, he said. More than twice as many women nearing 40 are unmarried today (at 28 percent), compared with 1960, when 13 percent were unmarried. In 1980, 9 percent of women in their early 40s were childless -- the number now is 16 percent.

Given the statistics on what makes women happy and their priorities, that "is a truly staggering rise," Rhoads said. The rise in unmarried women is, in part, fueled by the pervasiveness of casual sex, he said.

"Men are having too much fun to get married," he said. "Men are saying, 'Why should I grow up?'"

That hurts men, too. "It makes for immature men," he said. "Civilization is all about civilizing men. You make men less violent by getting them married off.'"

Rhoads also suggests there are two kinds of women -- one type of which on average have more testosterone than other women. The women with more testosterone, a minority, are more competitive and more interested in careers than low-testosterone women, who tend to be more domestic.

Rhoads considers his book to be pro-women. "Taking sex differences seriously will help both men and women live better lives, but women will gain the most," he said.

The policy implications of his findings are profound, he argues.

Boys and girls should receive different sex-education courses, he said: Boys should be taught about honor and girls that their risks in having casual sex are higher than for males. He said generous tax benefits should be given to parents of young children, if one parent stays at home. He said some parents are also giving bad advice to their daughters. Marriage should not in all cases be delayed for their careers.

Lane, the U.Va. history professor, is 73 and started the women's studies program at Colgate University before coming to Charlottesville.

"The range of behavior amongst men and women is enormous," she said. "Even if you assume women are not good mathematicians or engineers, then we should give them extra training. Even if we're wired differently, society should try to make us equal instead of just saying that's the way women are."

Rhoads' sex-differences classes are popular, especially with women.

"The women are on the edge of their seat," he said. "Women are on the front lines; that's why they're taking my course."

At a recent class with 14 women and six men, the women's hands were often waving in the air, while the male students were relatively quiet. The discussion was lively.

Rhoads said he has been reviled for his research and conclusions, noting that there are "narrow thoughts on campus, and it's as bad as it gets when you're talking about gender.'

"The debates should not be about whether important biologically based differences exist, but about their cultural and policy implications," he said.

Contact Carlos Santos at (434) 295-9542 or csantos@timesdispatch