What has madness to do with heredity? Concepts of heredity changed over the centuries. Emeritus Hans-Jörg Rheinberger reviews Theodor M. Porters' book in the Frankfurter Allgemeine Zeitung, which tracks continuities and breaks within the thinking about heredity since the 18th century. The collection of enormous amounts of data plays an early key role. A precursor of our modern data-drivenness?