On May 4, 2004, David Reimer committed suicide in Winnipeg. Thirty-eight years old, he had been a slaughterhouse worker and an odd-job man. He had also been both a boy and a girl, thanks to one of the darker episodes in the history of pseudoscientific hubris.

Born Bruce Reimer in 1965, David suffered a botched circumcision when he was eight months old. Most of his penis was burned off, and reconstructive surgery was too primitive at the time to restore it. Dr. John Money, a sexologist at Johns Hopkins University, persuaded Reimer's parents to have their son completely castrated and raised as a girl.

This was not simply a matter of trying to make the best of a bad situation. Money had been a leading exponent of the theory that children were born psychosexually neutral and could be assigned to either gender in the first years of their life. He had retreated somewhat from the most radical statement of this thesis, but stood by the central contention that when it came to sexual identity, nurture trumped nature. Bruce—now named Brenda—was an ideal test case. Along with everything else, she was an identical twin; so as an object of study, she came bundled with a built-in control.

Money trumpeted the results in his 1972 book Man & Woman, Boy & Girl, written with the psychiatrist Anke A. Ehrhardt; a more popularized account appeared in Sexual Signatures (1976), written with the reporter Patricia Tucker. By Money's account, Bruce/Brenda moved easily into her new identity. She soon "was observed to have a clear preference for dresses over slacks and to take pride in her long hair," he wrote in Man & Woman. She "was much neater than her brother, and in contrast with him, disliked to be dirty." Though it "needed perhaps more training than usual," she usually urinated sitting down, and when she did attempt to stand she was simply "copying her brother." She took to housework and to helping her mother in the kitchen, while her brother "could not care less about it." Her taste in toys ran to dolls, and despite some "tomboyish traits" she clearly was adapting to life as a girl.

Scientists with a less enthusiastic view of infant sex reassignment, Money added, had been "instrumental in wrecking the lives of unknown numbers of hermaphroditic youngsters."

For two decades this remained the accepted view of what happened. It helped influence many parents—approximately one or two for every 1,000 births, according to a 2000 paper in the American Journal of Human Biology—to opt for "corrective" sexual reassignment of their babies: not just hermaphrodites and victims of accidents like Reimer's, but boys born with abnormally small genitals. But then Dr. Milton Diamond, a longtime critic of Money's theories, reconstructed what had actually happened, co-authoring a paper on the case that was published in the March 1997 Archives of Pediatrics and Adolescent Medicine. Several follow-up stories appeared in the press, notably John Colapinto's excellent account in Rolling Stone; after Reimer agreed to make his identity public, Colapinto expanded the article into an engrossing book, As Nature Made Him (2000). Now that the patient was able to speak for himself, a very different story was on display:

• Brenda Reimer resisted being classified as a girl from the beginning. The first time she wore a dress, she tried to rip it off. She preferred her brother's toys to her own. (A toy sewing machine was untouched, Colapinto writes, "until the day when Brenda, who loved to take things apart to see how they worked, sneaked a screwdriver from her dad's tool kit and dismantled the toy.") She got into fights, insisted on peeing standing up, and ran into terrible problems at school, where the other kids quickly recognized her as someone who didn't fit the ordinary sexual categories. By the time she was 10, she was declaring that she wanted to grow up to marry a woman, not a man.

• Money's meetings with Brenda were a darkly comic study in how a scientist could refuse to see the evidence he didn't want to see, and how a subject can gradually learn to respond to his cues. Worse, his efforts to make her conform to his expectations were coercive and abusive. Her refusal to receive vaginal surgeries—her penis was gone, but her doctors had not yet put a vagina in its place—was met not with an effort to understand her stance but with a series of attempts to manipulate her into agreeing to the procedures. (She succeeded in avoiding the surgery but was compelled to take estrogen pills, though she flushed them when she could.) Also disturbing was Money's belief that Brenda, in Colapinto's words, "must understand at a very early age the differences between male and female sex organs." Not an objectionable idea in itself, except that Money accomplished it by showing Brenda and her brother pictures of adults having sex and by forcing them to disrobe and examine each other's genitals. Worst of all, he allegedly insisted, starting when the twins were six, that they "play at thrusting movements and copulation"—more bluntly, that they pretend to have sex in various positions while he watched. (This last detail has been disputed.)

• Finally, when Brenda Reimer learned the truth about herself, at age 14, she decided to start living her life as a boy. She had her estrogen-created breasts removed, took testosterone injections, changed her name to David, and eventually had surgery to create a penis. In 1990 David married. The allegedly successful transformation of a boy baby into a girl was in fact a complete failure.

For much of his career, Money's admirers saw him as a bold pioneer fighting puritanical reactionaries. This was his self-image as well. He touted himself as a defender of sexual liberation: for the rights of gays and other sexual minorities, for legalized pornography, for breaking down social taboos. But this seemingly libertarian attitude obscured an authoritarian core. When the truth about the Reimer case was exposed, the sexologist suddenly seemed much more repressive than the conservatives he hated.

Not that he acknowledged this. He told Colapinto that the press's embrace of Diamond's exposé was a product of right-wing media bias and "the antifeminist movement," insisting that "they say masculinity and femininity are built into the genes so women should get back to the mattress and the kitchen." By this time, though, his critics were emerging not just from the right but from the community of open intersexuals—people born with mixed or indeterminate gender. It turned out they don't like to be coerced by social engineers any more than they like to be coerced by the party of rigid sex roles.

It's the Intersex Society of North America that's leading the charge against the procedures Money championed, calling for "a model of care that is patient-centered, rather than concealment-centered." What this means in practice is summed up by a series of humane principles listed on the front page of the society's website, among them "Intersexuality is basically a problem of stigma and trauma, not gender," "Parents' distress must not be treated by surgery on the child," and "Honest, complete disclosure is good medicine." It's significant that groups like the Intersex Society focus their attention not on the scientific debate over the roots of gender identification, but on the proper way to treat those people who have landed in their position. It's interesting to compare and contrast the battles they're fighting with the battles being fought by transsexuals. One group is often cited by those who favor the nature side of the nature/nurture debate, while the other is embraced by the nurturists; one group wants to stop involuntary surgeries, and the other wants fewer barriers to voluntary surgeries. But both are essentially asking that they be allowed to decide how to live their lives; both want final say on what is done to their own bodies. That basic respect for the individual is what's missing from people like Money, who preach liberation but practice something much less attractive.

And David Reimer? I of course don't know what went through his mind when he decided to end his life. He had just lost his job, a big investment had failed, his marriage had split up, and his twin brother had died not long before, depressing events all. But surely the "therapeutic" abuse he had suffered was a factor in his death. It figured heavily, after all, in almost everything else that happened in his life.