It had been thought that Northern Europeans developed light skin in order to absorb more UV light to process more vitamin D, necessary for healthy bones and immune function. But a new study conducted by a team led by professor of dermatology Peter Elias from the University of California, San Francisco, shows that the changes in skin’s function as a barrier to water loss is more likely. The skin-barrier protein filaggrin is broken down into a molecule called urocanic acid, which Elias says is the most potent absorber of UVB light in the skin. “It’s certainly more important than melanin...