That men and women are different is an accepted tenet of popular culture—indeed, the success of everything from reality television shows to self-help books relies on the notion that la difference is a fact that yields happy, challenging, and occasionally comic results in the course of everyday life. The acknowledgment of difference has also provided fuel for many a political fire. One of the phrases often chanted during the previous century’s battle for women’s suffrage was, “For the safety of the Nation to the Women Give the Vote / For the Hand that Rocks the Cradle Will Never Rock the Boat.”

Yet amble any great distance along the path of sex differences, and you will soon find yourself with Harvard President Larry Summers, tripping painfully on the gnarled and dangerous roots buried there. Summers’s provocative comments about sex differences at an academic conference prompted Massachusetts Institute of Technology professor Nancy Hopkins to walk out of the room in protest. Hopkins, who now moonlights as the Ivy League’s self-appointed, publicity-seeking gender warden, several years ago spawned a similar media tempest by claiming, on paltry evidence, that women at MIT were the victims of institution-wide discrimination. Posturing provosts nationwide reacted with predictable alacrity, setting up panels and convening commissions at their own universities to root out this new but amorphous enemy: “unintentional” discrimination against women. Summers’s crime, in this context, was to have the temerity to state what science has long known about men and women, and to do so without worrying about offending the missish sensibilities of some female academics.

It is, in this clime, a great relief to discover Steven E. Rhoads’s Taking Sex Differences Seriously, an intrepid book that does much to advance the debate about why men and women are the way they are. A professor of public policy at the University of Virginia who has written previous books about economics and comparable worth legislation, Rhoads brings common sense and astute critical judgment to the difficult task of explaining sex differences. He begins with the word “sex” itself, noting, “When discussing the lives of men and women, we now use the term gender far more often than sex.” This, he argues, “reflects the assumption that any distinctions between the sexes’ traits, values, interests, skills and behaviors arise from societies’ rigid gender roles, which channel people’s thoughts and actions in stereotypical directions.”

But this assumption is incorrect. Drawing on extensive scholarly research in history, biology, sociology, child development, psychology, and economics, Rhoads examines a range of evidence about the biological basis of sex differences and in an appropriately dispassionate tone notes the intractability of certain facts: Men’s and women’s brains are structured differently, for example, and even from the earliest moments of a child’s life, the effects of these differences are impossible to ignore. “One-week-old baby girls can distinguish an infant’s cry from other noise; boys usually cannot,” Rhoads writes. “Three-day- old girls maintain eye contact with a silent adult for twice as long as boys,” and boys “are more interested than girls in three-dimensional geometric forms and in blinking lights” at five months of age. Children understand these differences intuitively, as anyone who has glanced at a kindergarten playground, where young boys and girls self-segregate by sex, can attest.

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But sex differences have an impact on far more than our individual impulses. If you’re wondering what is at the heart of our so-called culture wars, Rhoads offers an intriguing answer: cherchez la femme. The culture wars, so called, are really about women and their choices, and he adds an intriguing twist to the question of why: there are actually two kinds of women, he argues, “a majority who are traditionally feminine and others who are more like men than their sisters are.” The latter include women who have been exposed to higher levels of testosterone in utero, and throughout life exhibit more male qualities than other females. These “high-testosterone women are more assertive, more career-oriented, and more likely to have high-status and traditionally male-dominated careers,” he writes.

Although Rhoads does not posit a direct link between high levels of testosterone and a feminist worldview, he suggests that it might be one source of the tension between feminist and traditional women. Indeed, Rhoads’s book poses significant challenges to mainstream feminism, whose devotees continue to impart a feverish urgency to the denial of sex differences. So tendentious is mention of sex differences among feminists that even stating an indisputable scientific fact can get you into trouble. A few years ago, he recounts, when the American Society for Reproductive Medicine planned an educational ad campaign with messages such as “Advancing Age Decreases Your Ability to Have Children,” the National Organization for Women denounced the group’s “scare tactics” and “negative message” and pressured them to withdraw the advertisements. That feminists are loath to admit even this stark biological fact speaks to their determination to deny sex differences. But as Rhoads’s evidence suggests, and as critics of feminism have often noted, Mother Nature is not a feminist.

This denial of difference also supports feminists’ attempts to market the sexual revolution and its “freeing” of female sexuality as an unambiguous triumph for women. But the sexual double standard that has always allowed men greater promiscuity in sexual relations than women has not been eliminated; the sexual revolution only succeeded in making its effects more cruelly felt by even more women. Indeed, one of the greatest ironies of the sexual revolution was its naïve and ultimately unsuccessful revolt against biology. As Rhoads notes, “The old standard led to more happy young women than today’s does,” mainly because “the overwhelming majority of women come to dislike uncommitted sex.” Instead of society punishing women who are too promiscuous, as in the days of old, women now punish themselves (by risking disease and rejection), or blame men, or both. Explains Rhoads, “since the sexual revolution began, women have been thinking worse of men. In 1970, 32% of American women said that ‘most men are basically selfish and self-centered’; in 1989, 42% believed that.” In addition, “a 1993 Gallup poll reported that 40% of women were often or very often resentful of men,” and other researchers who study men’s attitudes about sex have found much higher levels of rage among women against men than among men against women. It appears that, as a society, we are becoming ever more incapable of embracing either the truth or the wit of the old observation: the battle of the sexes is the only conflict in which each side regularly sleeps with the enemy.

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Sleeping with the enemy is apparently not women’s biggest problem; it’s getting the enemy to do laundry and dishes. Feminists have long argued that women will achieve real equality only if they are relieved of their domestic burdens. Feminist theorist Susan Moller Okin, in Justice, Gender, and the Family (1989), argued, “any just and fair solution to the urgent problem of women’s and children’s vulnerability must encourage and facilitate the equal sharing by men and women of unpaid work, of productive and reproductive labor.” Okin envisioned a future “in which men and women participated in more or less equal numbers in every sphere of life, from infant care to different kinds of paid work to high-level politics.” To accept this worldview is to embrace the notion that the majority of women in the world are currently under the sway of a very destructive and very powerful form of false consciousness.

Rhoads sees something else: he sees women’s choices as an expression of innate differences they share with most other women, but not with men—differences that make the domestic sphere and the relationships formed within it more appealing to women than to men. “Women find special pleasure in small groups of women—a preference that gives them practice at establishing intimate friendships,” Rhoads writes, and women are better at detecting mood and emotion in others. By suggesting that biological differences might have something to do with women’s greater interest in domestic life, Rhoads is by no means trying to toss women back into pin curls and poodle skirts. Rather, he is suggesting that we recognize some permanent truths about the appeal of home and hearth for women—they are, in some small ways, hardwired to seek it.

Every woman might not choose to focus her energies on the home, but it is perhaps time to counter more vigorously the notion that the domestic life is nothing but a barrier to women’s advancement. As Rhoads observes, “Most politically active feminists value resources and power and the competitiveness that men employ to achieve status; they do not have comparable respect for typically feminine values and pursuits.” But it is not only feminists who fail to value domesticity; in a high-achieving market-driven society, the many small acts of thoughtfulness and labor that go into making a welcoming and smoothly functioning home are rarely given their due.

Beyond improvements in personal relations between men and women, there are serious policy implications to taking sex differences seriously. Perhaps one of the clearest attempts to deny sex differences in public policy has been the enforcement of Title IX of the Educational Amendments of 1972, particularly in college athletics. As Rhoads notes, the premise for current enforcement of this well-intentioned antidiscrimination statute is that men and women have absolutely equal interest in college athletics, so college sports teams ought to contain the same proportion of men and women as in the student body as a whole. Given the extensive research on biological explanations for aggression and competition—and their greater prevalence among men than women—it is impossible to argue with his conclusion about Title IX. The law “became a pernicious form of social engineering only when it became part of a numbers game and an ideological agenda insisting that the way women are socialized (rather than the way they are) keeps them from loving sports as much as men do.” Thus, “only when we begin to take sex differences seriously enough to see that men are intrinsically more attracted to sports… will we be able to design public policies that are just, functional, and sensible.”

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Government-funded daycare is another arena in which recognition of sex differences might yield a different public policy outcome. Germaine Greer once suggested, “the real theater of the sex war is the domestic hearth,” but today, the hearth is not where a lot of women spend most of their time. Although only 36% of women with children under the age of one work full-time, a great many work part-time, and they are turning their children over to others to care for when they do. Many readers will not like what Rhoads has uncovered about nonmaternal care and its effects on family life, marriage, and children, for it forces us to confront some of the costs of our own ambitions and desire for professional fulfillment. One study cited by Rhoads found that “young, highly educated, and occupationally successful fathers in dual career marriages are less satisfied with their work, marriages, and personal lives than similar men who are sole providers for their families,” largely because they feel that domestic and childrearing tasks are not being granted enough attention. As for the children, citing the findings of many major studies of day care, including studies published by the National Institute of Child Health and Human Development, Rhoads writes, “after holding other relevant variables constant, researchers found that new mothers with relatively extensive work experience outside the home—more than thirty hours per week—produced children who at age three had poorer cognitive and verbal development than children of stay-at-home mothers.” Although Rhoads’s is not the last word on the debate over daycare, he offers important evidence that its benefits to parents might come at the expense of their children.

One area to which Rhoads devotes too little attention is how sex differences have been treated as a matter of law, and he breezes past debates over the use of the “reasonable person” rather than the “reasonable woman” standard that people such as Justice Ruth Bader Ginsburg (whose name he misspells) have developed. But this is a quibble. Feminists are certain to decry Rhoads’s argument that we take sex differences seriously, but the rest of us shouldn’t. His message is most important for young women, for they are the ones who need to exercise more thoughtful judgment about sex, marriage, childbearing, and childrearing. Rhoads’s book might be especially useful for men and women in college, who are thinking about the kinds of lives they would like to lead. Perhaps with some reflection they might begin to see the truth in Rhoads’s suggestion that our differences should not be the source of bitterness or resentment, but the recipe for genuine complementarity of the sexes. Men’s “sense of duty and capacity for sacrifice will be brought forth more readily if women will say ‘no’ to casual sex and give them time and motive to turn their lust into love,” Rhoads writes. “The idea that women can transform men for the better is out of fashion, but as the social science on the effect of marriage makes clear, it is undeniably true.” Whether young women will be willing to take on the role of arbiter, and in the process transform relations between the sexes, remains to be seen, but if they read this book they will at the very least have heard a persuasive argument for why they should.