Girls in an isolated Caribbean village become male and grow penises when they hit puberty due to a rare genetic disorder.

It is estimated that one in 90 children born in Salinas in the Dominican Republic make the transition by the time they reach 12.

It is so prevalent there that it is no longer considered abnormal and the children are simply referred to as the ‘guevedoces’ – which literally translates as ‘penis at 12’

The children, known as pseudohermaphrodite, are explored in BBC2 series Countdown to Life – the Extraordinary Making of You.

The rare genetic disorder is caused by a missing enzyme which prevents the production of a type of male sex hormone – dihydro-testosterone – in the womb.

As a child, he did not have a penis and was brought up as a girl. Now 24, he is physically and biologically male – a process that started when he was seven years old.

He said: ‘I remember I used to wear a little red dress. I was born at home instead of in a hospital. They didn’t know what sex I was.

All babies in the womb, whether male or female, have internal glands known as gonads and a small bump between their legs called a tubercle.

At around eight weeks old, male babies who carry the Y chromosome start to produce dihydro-testosterone in large amounts – this turns the tubercle into a penis. For females, it becomes a clitoris.