This condition of gender transition is so common that the children of Salinas afflicted with it are referred to as Guevedoces, or ‘penis at 12 years’.
This unusual condition was first discovered and described in the 1970s when a scientist from Cornell visited the island.
Babies usually form male sex organs after around eight weeks in the womb, with the change triggered by hormone dihydro-testosterone. A handful of babies, however, do not have the enzyme that triggers the hormone surge and consequently they will not form male genitalia until they reach puberty, when there is another surge of testosterone.
BBC Two’s Countdown to Life – The Extraordinary Making of You explores this remarkable example of human diversity and admits that sometimes even the most complex, crucial to our species processes can occasionally go wrong.