For decades, scientists have studied animals living in or near the Chernobyl Nuclear Power Plant to see how increased levels of radiation affect their health, growth, and evolution. A study analyzed the DNA of 302 feral dogs living near the power plant, compared the animals to others living 10 miles away, and found remarkable differences. On April 26, 1986, the Chernobyl Nuclear Reactor in northern Ukraine—then part of the Soviet Union—exploded, sending a massive plume of radiation into the sky. Nearly four decades later, the Chernobyl Power Plant and many parts of the surrounding area remain uninhabited—by humans, at least....