Why Girls in This Town Become Boys at Puberty

Girls born in a particular village in the Dominican Republic may not grow up as biological females after all. A little more than 1% of them will develop a penis at age 12, making them what locals call "guevedoces"—literally, a "penis at 12," the Telegraph reports. "I remember I used to wear a little red dress," says 24-year-old Johnny, one of about 6,000 villagers in the isolated town of Salinas. "They didn’t know what sex I was. I went to school and I used to wear my skirt ... When they bought me girls' toys I never bothered playing with them. All I wanted to do was play with the boys." Turned out that Johnny suffered from an unusual genetic disorder caused by a missing enzyme, called 5-α-reductase, which stops a powerful male sex hormone from surging into wombs that carry the male Y chromosome.

That surge of dihydro-testosterone normally occurs at about eight weeks, and turns the tubercle—a little bump between the legs of babies in the womb—into a penis. Well, Y-chromosome babies born without that hormone blast are born looking female with what resembles a vagina. But at puberty, when the next testosterone surge comes along, the male sex organ finally appears and their voices grow deeper. At that point the "guevedoces" may be teased in school, one tells the Telegraph, but they are generally celebrated by Dominicans (unlike Sambian villagers in Papua New Guinea, who shun people with the disorder). And despite less facial hair and smaller prostate glands, "guevedoces" can generally live as normal males, though the BBC reports that some get an operation in order to stay female. Experts believe that the villagers' isolation has caused the condition to persist. (A set of South Carolina parents recently sued after doctors decided their child was female.)