Animals can pass the damaging effects of nighttime light exposure to their offspring, a new study has found, adding to a growing body of evidence that there’s a health cost to our increasingly illuminated nights. Hamster pups are born with weakened immune systems and impaired endocrine activity when their parents don’t receive a natural mix of daylight and darkness prior to mating, found researchers. This research aimed to determine whether parents were passing along possible modifications in genetic messaging, known as epigenetic changes.