As almost everyone above the age of 3 knows, the Harry Potter novels depict a world divided into people who possess magical powers (wizards and witches) and those who do not (Muggles). Not everyone can be a wizard; indeed, after careful review of the evidence, the authors of the Nature letter concluded that wizards evidently inherit their gifts from their parents as predicted by the theories of the 19th-century geneticist Gregor Mendel.