Hawbecker says his penis size and absent testicles, removed in childhood, don’t hurt his ability to love and make love to his wife. "I very happily engage in sex whenever I can. You have to be creative, and not so focused on genitals," he says. As for his own pleasure, "My penis does everything you'd expect a penis to do -- it's just small."

Hawbecker says he thinks like a man; with his clothes on, he looks typically male too. And yet, he says, "I guess I've never really felt like I fell neatly into the camp of guys. I love to cook. I love to take care of things around the house. I hate the Three Stooges and I don't like football." Often, he thinks about the female he might have become; where she'd be right now. "I think she'd be OK. I could've done 'girl' too. I could be happy that way, too. That's what's mind-boggling."

Medical literature says that about one in 2,000 babies is born like Hawbecker or Harmon-Smith, with uncommon variations of genitals and gonads, or sex-conditioning hormones that don't match sexual organs. About one in 1,000 women has three X chromosomes instead of the usual two; some people have had as many as four X chromosomes -- plus two Ys. Some women have facial hair, some men don't. Breast size, voice timbre and body structure, all generally accepted cues, also can contradict chromosomal identity.

"The basic story is, it isn't simple," says Alison Jolly, a Princeton evolutionary biologist who studies ringtail lemurs in Madagascar. "It's all just more complicated than people will admit." In the first few weeks of life, every human embryo develops the equipment for both sexes, the foundations for both ovaries and testes. At about eight weeks, a chemical chain of events stimulates one set to disintegrate. One week later, the external genitalia begin to form -- and usually, to match what's left inside.

All this seems to be triggered by a spot on the Y chromosome called SRY, for "sex-determining region, Y chromosome," that scientists have dubbed the "master switch." Throw it, they say, and a chain of events run mostly by genes on the X chromosome leads to the development of testes and the production of male hormones. Without SRY, females continue along what molecular biologists have dubbed the "default" pathway. In February, however, researchers reported the first evidence that an active signal stimulates female development, too.

Of course, there's a lot more going on as well -- much of it still not even vaguely understood. A wash of hormones primes the brain for one sex or another, though not always the same as the one indicated by genitalia at birth. Jolly suggests looking at sex as statistical -- a compendium of characteristics that, when plotted on a graph, looks like a couple of camel humps. One set of features tends to be viewed as male and the other female. The section in between is as normal as the outlying regions in the land of "super-macho" and "super-fem."

From classical antiquity through the Renaissance, anatomists thought there was just one sex, and it was male. Female bodies simply mirrored the male reproductive organs -- with the vagina an inverted penis; the ovaries, interior testicles. During the 18th century, the idea of two separate sexes took hold. Then in 1993, Anne Fausto-Sterling, a well-regarded biologist and feminist studies theorist at Brown University, raised a ruckus when she proposed that male and female were not enough. In a tongue-in-cheek proposal, she recommended five categories in all.

Some people seized upon the idea as a revelation finally explaining their own bodies. Others felt the thesis went too far. Fausto-Sterling says her readers were taking her too literally. She has abandoned the proposal -- which at root simply challenged people to think differently about sex -- and now wants to eliminate the term from our vocabulary. "There is no sex; there's gender," Fausto-Sterling says.

Fausto-Sterling argues that scientific discoveries about the ways our bodies work employ cultural understandings and, as in the male "master switch" and female "default pathway," the language of existing social models. Whenever faced with a lack of clarity, surgeons get out the ruler and make a choice. "There's a set of decisions by which we're going to socially agree what is a penis. How we organize the continuous variability that nature offers us is what gender is about," Fausto-Sterling says. "What we call the truth of the body is also a cultural view of the body through a scientific lens."

Both the scientific and social interpretations are increasingly complicated and controversial. The International Olympic Committee has found itself at the center of the uncertainty. The first shock came when Hermann Ratjen, who ran as Dora Ratjen for Germany in the 1930s, confessed in 1957 that he had disguised himself at the request of the Nazi Youth Movement. So in 1966, as the opportunities for women to compete expanded rapidly, a panel of judges began checking female athletes for vaginal openings, overlarge clitorises, a penis or testicles. By 1968, chromosome testing replaced these "nude parades," and in 1992, a more sophisticated instrument to hunt for the SRY gene was adopted. But as the technology advanced, so did the confusion.

Five women out of 2,406 tested "male" in the 1992 Barcelona Olympics. Eight women in the 1996 Atlanta games didn't pass as females. In February, the Athletes' Commission of the International Olympics Committee urged its parent organization to do away with sex analysis entirely and rely instead on observed urination during drug testing to pinpoint any likely imposters.

Anatomy, gonads, hormones, genes, rearing, identity and even the presumptions of others all play into a person's sex. "To select only one, the genetic sex, out of a large number of sex-determining factors and analyze for that one is scientifically incorrect," says Arne Ljungqvist, head of the International Amateur Athletics Federation doping commission.

Both women and men in sports have begun to accept a broader definition of what a "woman" is, accepting those with chromosomal variations and sometimes even testes. Intersex activists hope pediatric specialists also will quit worrying about what those jock straps contain -- and indeed, some already have.

William Reiner, who started out as a urologic surgeon, went back to school after witnessing the misery of children living with the results of sex-correction surgery. Now a child psychiatrist at Johns Hopkins University, he says the most important sex organ is the brain. Reiner doesn't buy any theories about a range in biological sex; in fact he thinks it's quite binary. All the more reason to step back from aggressive enforcement, he says. Sure, go ahead and assign sex at birth, he suggests, but in the final analysis boys will be boys, girls will be girls, and they know what they are better than any parent or doctor.

Some surgeries are medically necessary, and many seem to turn out just fine. Reiner hopes to sort out some of the mysteries by following the lives of 700 children born with atypical genitals, 40 of whom had their sex reassigned at birth. "The kids are going to tell us the answers," he says. Cheryl Chase thinks she knows some already. She founded the network that grew into the Intersex Society of North America, a clan of 1,400 whose anatomy doesn't fit the binary ideal. Born with both ovarian and testicular tissue, Cheryl started out life as Charlie. But doctors decided later that since she was potentially fertile and had a short penis, she'd be better off as a girl. Her parents changed her name, threw away photographs and birthday cards and had her clitoris removed when she was 18 months old. Her ovotestis came out at age 8. She was in her 20s and living as a lesbian in the 1970s when she dug up the truth about her birth and life as a boy -- making her feel like an imposter in her own community. And for her, like many others who had surgery on their genitals, the missing parts and scarring made sex more likely to bring pain than pleasure.

The Intersex Society doesn't oppose assigning gender at birth. Instead it -- and now some medical specialists -- urges parents and doctors to refrain from surgery and be open to a change in sex identity later.

But Chase, for one, isn't waiting for culture to come to terms with biology. "I'm focused on practical changes that come quickly, not pie in the sky," Chase says. "I would much rather keep my clitoris and have orgasms than have a box to check off."

Helena Harmon-Smith, Patrick's mother, says she wants children like her son to be allowed their own decisions -- and more than anything, to be recognized as real. "My son was one of the lucky few -- because he is technically both. He can be boy or girl," she says. She will never forgive Patrick's doctor for making the choice for him.

next: The True Story of John / Joan