IN A remote village within the Dominican Republic, an extraordinary case of boys not growing penises until puberty has been uncovered.

The isolated community of Salinas is highlighted in a new BBC documentary series titled ‘Countdown to Life — the extraordinary making of you,’ where journalist Michael Mosley follows the life of 24-year-old Johnny, who was raised as a girl because he didn’t develop male genitalia until early adolescence.

Johnny and others like him, are referred to as “Guevedoces” which translates to “penis at twelve.” The community has become so accustomed to the late genital development among pre-teens, it’s now considered normal.

Johnny, like many others in his community, was born with what appeared to be a vagina.

So why does this late development happen?

It’s a result of enzyme deficiency.

Regardless of the sex, all babies have internal glands called ‘gonads’ and a bump between their legs called a tubercle. At around two months of development, the ‘sex’ hormones emerge. If you are destined to be a boy (therefore, have a Y chromosome) the tubercle will become a penis. For a baby carrying the X chromosome (a girl) they will develop a clitoris.

In an article written by Mosley for BBC Magazine, a study conducted by Dr Julianne Imperato-McGinley, from Cornell Medical College in New York, revealed that ‘Guevedoces’ were deficient in a enzyme called ‘5-alpha-reductase.’ This deficiency, which is relatively rare around the rest of the world, was increasingly more common within the Dominican Republic.

So when the Guevedoces ‘girl’ reaches puberty, there is a second production of testosterone, and as a result, testes and a penis are developed.

More on the study and the story of Johnny can be found here.