CATCHING evolution in action is hard. The best-known examples are those where human action, in the form of pesticides, herbicides or drugs, has intentionally made the world a nastier place for some specific group of creatures, and natural selection has pushed back to create resistance (see article). But a group led by Timothy Mousseau of the University of South Carolina, Anders Moller of the CNRS, in France, and Ismael Galván of the Doñana Research Station in Spain has now, in a paper in Functional Ecology, provided an example of selection responding to a human action that was most definitely unintentional: the explosion and fire at a nuclear reactor in Chernobyl, Ukraine, 28 years ago.

Dr Mousseau and Dr Moller knew from previous work that birds living near Chernobyl have better survival rates than those living near Fukushima, in Japan, where a serious reactor accident happened in 2011. They suspected that was because the Ukrainian birds had had time to evolve resistance. They therefore sent blood and feather samples from 120 birds of 13 species they collected from both high- and low-radiation regions around the defunct reactor at Chernobyl to Dr Galván, who looked for genetic damage in them and also analysed their levels of glutathione, an antioxidant that mops up highly reactive (and therefore harmful) molecules created when radiation hits biological tissues.

In those birds taken from low-radiation zones the average concentration of glutathione was 450 micrograms per gram of body mass; in high-radiation areas it was 725 micrograms per gram. Moreover, the higher a bird’s glutathione level, the lower the amount of genetic damage Dr Galván could spot in its cells. Birds in high-radiation zones, then, seem to have evolved to deal with the threat, just as Darwin would have predicted.