Biology stands on the brink of a shift in the understanding of inheritance. The discovery of epigenetics hidden influences upon the genes could affect every aspect of our lives. At the heart of this new field is a simple but contentious idea that genes have a ‘memory’. That the lives of your grandparents the air they breathed, the food they ate, even the things they saw can directly affect you, decades later, despite your never experiencing these things yourself. And that what you do in your lifetime could in turn affect your grandchildren. The conventional view is that DNA carries all our heritable information and that nothing an individual does in their lifetime will be biologically passed to their children. To many scientists, epigenetics amounts to a heresy, calling into question the accepted view of the DNA sequence a cornerstone on which modern biology sits. Epigenetics adds a whole new layer to genes beyond the DNA. It proposes a control system of ’switches’ that turn genes on or off and suggests that things people experience, like nutrition and stress, can control these switches and cause heritable effects in humans. In a remote town in northern Sweden there is evidence for this radical idea. Lying in Överkalix’s parish registries of births and deaths and its detailed harvest records is a secret that confounds traditional scientific thinking. Marcus Pembrey, a Professor of Clinical Genetics at the Institute of Child Health in London, in collaboration with Swedish …