During the mid-70s in the Dominican Republic, eighteen young girls all born around the same time physically transformed into boys once they hit adolescence.
These individuals were all genetically male. However, they lacked the enzyme that convert testosterone to dihydrotestosterone (DHT), the hormone response for fetal development of male external genitalia. Thus, XY individuals with this syndrome are born with un-descended testicles and lacking male external genitalia. These individuals appear female, however they will still produce elevated levels of testosterone once puberty hits. And so at about twelve, the girls' voices deepened and they grew mustaches. Also, since their genitalia were now sensitive to testosterone, their testicles descended and the clitoris grew into a penis. The girls became boys.
Testosterone at lover level during the birth by itself can only do part of the gender job.
The development of a penis is dependent on a testosterone product called DHT during earlier developmental stages. People without DHT are therefore born with female genitalia. When puberty started, the testosterone produced at a much higher level from the testicles hidden in the children’s abdomens acted on the brain and pushed their body to finish the gender job – just a little late. According to anthropologists, the villagers in this macho culture rejoiced when they found out they had a son rather than a daughter. The villagers made up a new word to label these children. It was guevedoces which means penis at twelve.