There's not a huge amount of evidence that the hormesis hypothesis is correct, but there is some, yes. Nevertheless, even in the absence of a benefit to the individual, there is little doubt that low levels of radiation, called background radiation, are a large part of the very driving force of evolution itself. Organisms have evolved a large number of defenses against low-level radiation, such as the ability to repair DNA, but still ionizing radiation induces mutations from time to time, and if these mutations prove beneficial to the organism in some way, it may have some slight reproductive advantage over other organisms. In this way, evolution slowly progresses and new species arise. In a very real sense we owe our existence to radiation, including the incessant bombardment of cosmic rays.