The loss of anatomical features is a frequent evolutionary event. For example, humans and other great apes have lost their tails and whales have lost their legs. The most convincing evidence comes from the presence of vestiges in fossils. Unfortunately, the fossil record mostly preserves vestiges of hard structures such as bones or teeth. Consequently, resolving the evolution of soft-tissue structures such as muscle or brain tissue requires analytical methods. A team of researchers from the Max Planck Institute of Molecular Cell Biology and Genetics, the Max Planck Institute for the Physics of Complex Systems, the Senckenberg Natural History Collections Dresden and the Natural History Museum Frankfurt now provides a new approach to resolve the evolution of soft-tissue structures, focusing on the evolution of testes in mammals.