Is it a girl's nature to nurture?

"Biology is destiny" has a new champion, and he's a man whose ideas about the nature of women are provoking debate - even ire - from London to Toronto to Denver.

Michael Gurian's assertion that girls are molded primarily by physiology, and very little by culture or how they are raised, is reviving a long-dormant debate over "nature versus nurture." It's a discussion that feminists, if not a broad swath of women in developed countries, thought had been resolved in favor of freedom of choice and unlimited possibilities.

But Mr. Gurian's recent book, "The Wonder of Girls" (Pocket Books, $26), asserts that women's "primal need" to be mothers, to nurture children, overrides all else - and that women who make trade-offs to pursue careers or support the family will come to regret them.

For Gurian, "hormones rule" is familiar territory. He launched the "boys' movement" in the 1990s with "The Wonder of Boys" and "The Good Son." In those books, the family therapist and researcher claimed that male biochemistry shaped everything from boys' attitudes to learning style. Those books drew praise from parents and educators desperate for advice on raising boys.

All of Gurian's books rely on his synthesis of brain studies to support his belief that boys are hard-wired for action and risk-taking, and that girls are destined to be nurturers. Fundamentally, he argues that comprehending girls - their moods, interests, and styles of communication - requires understanding their biology, which includes hormonal swings dictated by the brain. These fluctuations prepare a girl ultimately to be a mother, and so serve a purpose that girls and society should learn about and honor.

"As biochemical research grows, hormones will get increased credit for female existence, success, happiness, self-esteem, and quality of life," Gurian writes. "That is how powerful they are."

A bit further on, he continues, "Hormones change everything, not just a few things, and they don't just change a girl into a woman, they are to a great extent, the woman herself." [Italics are the author's.]

The problem, say critics, is not with Gurian's reading of brain science, but rather with his conclusions about girls and his characterization of feminism, which he says holds women back.

Women's groups have called Gurian's book a "throwback." As one girls' advocate puts it, "This takes us right back to the notion of 'men hunt, women make babies.' "

Gurian dismissed the criticism in a telephone interview from his office in Spokane, Wash. He says he hopes that girls - his two daughters included - feel they can pursue any career they choose, but should also remember that they are designed differently from boys. He hopes they will learn to value the nurturing instinct.

Feminism, he claims, teaches girls that to be successful, they have to turn away from "their natures" to compete with men.

"I'm not antifeminist," he says, "but the feminist approach says that when women disconnect [from others] and find their power source as individuals, then they will be better, more successful. But that creates a difficulty. If a woman has children, she may find that she's cut herself off from a lot of the support systems. That can make women feel very alone."

But his interpretation of feminism doesn't ring true with many women.

"Feminism is not a static term," says Whitney Ransome of the National Coalition of Girls' Schools in Concord, Mass., "just like equality is not a static term." As an evolving movement, feminism has many facets, it's not one monolithic block, she says. She believes that Gurian indulges in stereotypes when he claims that feminists encourage a victim mentality and support girls' education at the expense of boys', or when he suggests that women's groups don't support marriage, and that their goal is a genderless society.

"Feminists want fairness, for both girls and boys," Ms. Ransome says.

Gurian doesn't discount the feminist movement's importance to society over the past 30 years. His view is that feminism works best in a crisis - where women must be empowered to take action against abusive partners, for example. But the flaw, he says, is that "feminism hasn't helped women stage their lives."

In the book, Gurian lays out the roughly four stages, or seasons, of a woman's life, which, he says, are governed by the biological urge to nurture children. These are: trying out love relationships; mothering; detaching from children as they grow; and then, when children are grown, finding new pursuits.

He is adamant about the penalty if this doesn't happen: "We don't recognize how much our civilization exists to make sure that the phase of life in which women are raising kids is absolutely sacred and protected. Because if it's not, we are going to raise children who are unhappy, depressed, and violent."

Gurian accuses women's advocates of glossing over brain studies of gender differences. He has said that they find it more expedient to stay focused on cultural research that, for example, attempts to link girls' lack of self-esteem with negative media images.

Women's groups respond that the issues are more complex, and that they do look to science. Ransome says her organization relies on data from at least one of the same six neuroscience researchers whom Gurian cites in his footnotes.

"We are interested in serious brain research," she says. "We know there are brain differences [between girls and boys], but those differences don't determine your destiny."

To gauge reaction to "The Wonder of Girls" in the scientific community, six academic researchers in neuroscience and neuropsychology were contacted. Several women's organizations were also called. The feminists all knew of Gurian's book and several were familiar with its contents. But none of the scientists had heard of it, and they declined to comment further without reading it.

However, one of the scientists, Doreen Kimura, a neuropsychologist and researcher in Burnaby, British Columbia, suggested taking a look at one of her papers on sex-based brain differences.

In it, she writes that evidence supports the existence of structural differences in the brains of men and women, which "to a certain extent" may be wired from birth.

"Nevertheless, she says, "in the larger comparative context, the similarities between human males and females far outweigh the differences."

She goes on: "Imaging techniques have begun to uncover possible functional brain differences between men and women, but these need to be rigorously vetted in future [studies]...."

For his part, Gurian says he is convinced that anyone reading the same brain studies and sitting in on his therapy sessions would reach the same conclusions about girls as he has. That is: If girls understand their biological makeup and know what nature is pushing them toward, they will be happier and less at war within themselves, whether they eventually choose a home and family or a career.

But he's aware that critics smell a conservative social agenda at work, which he denies. "People say, 'He's a guy who is putting all the burden of child-rearing on women.' Well, of course not. I've written books to tell men that they're here not just to [be the breadwinners] but to make it possible for women to stage their lives and for men to be more attached [to their families]."

Gurian continues: "It's not just a woman's issue. Yes, a woman's biology is affected when she gives birth, and a man's is not. But socially and emotionally, it's a man's issue, too."

In Michael Gurian's book "The Wonder of Girls," he writes of teaching his daughters "about the natural stages to a woman's life," including the "four stages of the motherhood process."

"Our understanding of female nature shows us a primal need among most females to be mothers and to be supported, for a period of many years, by husband, extended family, and culture in performing the duties and experiencing the unique love of mothering.

"To fully mother, a woman may, throughout her mothering years, keep up a profession - in the cases of many, even most women in our economic system, this may be necessary and very helpful - but she will regret her life if her profession is pursued to the detriment of fully experiencing motherhood.

"If she does choose to work professionally - part time or full time ... she will need to make sure her children have a 'second mother' (this could be an at-home dad) ... who nurture[s] the child with her, with consistency of attachment to the child.

"We teach our daughters to plan their mothering years toward the highest possibilities for themselves and their families, but never to sacrifice the care of the child to any other social goal."