Since 1859, when Darwin’s classic work “On the Origin of Species” was published, we have known that populations change over the course of time. The ability to adapt to changing surroundings is the basis for evolution and is crucial for animals and plants to come to terms with new environmental conditions, for example as a consequence of climate change. Despite the obvious importance of the process, however, we still do not understand the underlying mechanisms. It is clear that organisms change their DNA in response to selection pressures. But how?