Nutritional scientist Sera Young presents her new book, "Craving Earth." Pica--the urge to eat clay, starch, ice and chalk--has been a phenomenon among humans, particularly women, for a very long time. Dr. Young’s study seeks to answer why some people engage in this curious behavior , also shedding light on the properties that the non-food substances associated with pica possess. Touching on the history of medicine and drawing from a global body of literature, she constructs a bio-cultural framework for understanding pica, identifies its most avid partakers (pregnant women and young children), tests scientific hypotheses, and describes the potentially healthful and harmful effects. Merging history with detailed case studies, Dr. Young’s book offers a rich source of information—helpful to a broad variety of researchers and health practitioners—about a nutritional issue that is still only poorly understood.