Evolution takes place constantly, everywhere in nature. Nevertheless, it is always exciting for biologists to observe evolution "in real time." One such opportunity for observation is currently being presented by the internal clock—the innate sleep-wake rhythm—of the fruit fly Drosophila melanogaster. In fruit flies, a certain variant of a "clock gene," which presumably first appeared in southern Europe 300 to 3000 years ago, is spreading northwards, for example, to and within Scandinavia. Researchers have observed this phenomenon but have not yet been able to fully explain it. Based on laboratory studies, a team led by the neurobiologist Prof. Ralf Stanewsky from the University of Münster (Germany) is the first to offer an explanation for this phenomenon.
