ISLAND LIFE is famously idyllic, but it’s long been known that islanders tend to experience disproportionately high rates of some rare genetically transmitted diseases. Faroe islanders, for example, who live on an archipelago in the North Atlantic Ocean, have a much higher-than-average incidence of carnitine transporter deficiency (CTD), a condition that prevents the body from using certain fats for energy. Inhabitants of Gran Canaria, meanwhile, an island off the north-western coast of Africa, are far more likely than average to have familial hypercholesterolaemia, a condition where the liver cannot process cholesterol effectively.