Why do certain easily preventable diseases persist in the modern world? Renate Lellep Fernandez sheds light on this paradox by investigating the high incidence of iodine deficiency disease (IDD) among mountain villagers in northern Spain. Just as the mystery of non-prevention leads the author far beyond the confines of a single place, so are the experiences of these villagers rich in lessons for biocultural anthropology and public health in many contexts...