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Gender: We're a bit of both

by Eric vilain

“Duos habet et bene pendantes!”
(“He has two and well hung!”)

It was the moment of truth. The ultimate test before the coronation. A deacon would extend his hand below the robe of the future pope and check for the presence of two testicles. Middle Ages legend has it that this rite was started after Joan, an English cross-dresser, managed to get elected pope in 855. But her secret was discovered two years later because of an ill-timed childbirth.

Will we soon witness such surreal examinations in our city halls? After all, if the Constitution allows only marriages between a man and a woman, county clerks had better make sure they’re issuing licenses legally. Patting down the two male organs would ensure sex identification. Or would it?

In reality, sex isn’t so straightforward. Take testicles as a defining male characteristic. Are individuals with only one testis “real” men? The “two-testicles rule” would disqualify about 3% of male newborns a year — roughly 4.5 million Americans. Does one need to produce active sperm or eggs to be considered a man or woman? Adding a fertility criterion would eliminate millions more from both categories.

If conventional wisdom cannot easily define men and women by a simple look at the private parts, science should help us distinguish between the sexes. Since 1921, we have known that women have two X chromosomes and men an X and a Y chromosome. This is the fundamental genetic distinction between men and women.

Still, it’s been difficult to find clear-cut differences. The International Olympic Committee (IOC) has struggled with the science of “sexing” individuals for years — often after high-profile cases of gender confusion. In 1990, scientists learned that a gene called SRY on the Y chromosome makes fetuses become boys and not girls. In 1992, an Olympic test was perfected to detect the presence of the SRY gene.

But there are exceptions to the chromosome rules: females with a Y chromosome and males with no SRY gene. At the Sydney Olympics in 2000, the IOC decided to “refrain from performing gender tests,” conceding that no single test provides a complete answer.

Identifying the gender of intersex and transsexual individuals poses an even more complex challenge. Intersexuality, defined as the presence of “ambiguous genitalia,” makes it impossible to tell easily whether a newborn baby is a boy or a girl. Transsexuals believe they have been born in the wrong body and often pursue a difficult and painful process of surgical reassignment. But courts often don’t recognize the change of sex and invalidate spousal rights of transsexuals.

Sex should be easily definable, but it’s not. Our gender identity — our profound sense of being male or female — is independent from our anatomy. One of the most powerful lessons of modern genetics is the discovery of genetic variability in humans. We are all quite different from each other if we look at our genes. We are, in fact, so different that we cannot be easily categorized. From a biological perspective, we are all a little Jewish and a little black. And we are all a little between a man and a woman.

Vilain is associate professor of human genetics, pediatrics and urology, and chief of medical genetics at the David Geffen School of Medicine.