Clues from a Somalian cavefish about modern mammals’ dark past

After millions of years living in darkness, a species of blind cavefish has lost an ancient system of DNA repair. That DNA repair system, found in organisms including bacteria, fungi, plants, and most other animals, harnesses energy from visible light to repair DNA damage induced by ultraviolet (UV) light. The findings are intriguing in part because only placental mammals were previously known to lack this system.