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.

Animals of all kinds have thrived in humanity’s absence. Living among radiation-resistant fauna are thousands of feral dogs, many of whom are descendants of pets left behind in the speedy evacuation of the area so many years ago. As the world’s greatest nuclear disaster approaches its 40th anniversary, biologists are now taking a closer look at the animals located inside the Chernobyl Exclusion Zone (CEZ), which is about the size of Yosemite National Park, and investigating how decades of radiation exposure may have altered animals’ genomes—and even, possibly, sped up evolution.

Scientists from the University of South Carolina and the National Human Genome Research Institute have begun examining the DNA of 302 feral dogs found in or around the CEZ to better understand how radiation may have altered their genomes. Their results were published in the journal Science Advances in 2023.

“Do they have mutations that they’ve acquired that allow them to live and breed successfully in this region?” co-author Elaine Ostrander, a dog genomics expert at the National Human Genome Research Institute, told The New York Times. “What challenges do they face and how have they coped genetically?”

The idea of radiation speeding up natural evolution isn’t a new one. The practice of purposefully irradiating seeds in outer space to induce advantageous mutations, for example, is now a well-worn method for developing crops that are well-suited for a warming world.

Scientists have been analyzing certain animals living within the CEZ for years, including bacteria, rodents, and even birds. One study back in 2016 found that Eastern tree frogs (Hyla orientalis), which are usually a green color, were more commonly black within the CEZ. The biologists theorize that the frogs experienced a beneficial mutation in melanin—pigments responsible for skin color—that helped dissipate and neutralize some of the surrounding radiation.

This made scientists ponder: could something similar be happening to Chernobyl’s wild dogs?

The study uncovered that the feral dogs living near the Chernobyl Power Plant showed distinct genetic differences from dogs living only some 10 miles away in nearby Chernobyl City. While this may seem to heavily imply that these dogs have undergone some type of rapid mutation or evolution due to radiation exposure, this study is only a first step in proving that hypothesis.

However, one environmental scientist, speaking with Science News, says that these studies can be tricky business, largely due to the fact that sussing out radiation-induced mutations from other effects, like inbreeding, is incredibly difficult.

And in the time since the original study was published, other researchers have dug into this question and come up with competing results. In fact, a study published nearly two years later confidently asserts that we can cross radiation off the list of explanations for the current state of the Chernobyl canine population. Published in the journal PLOS One by scientists from North Carolina State University and Columbia University Mailman School of Public Health in New York, this new genetic analysis looked at the chromosomal level, the genome level, and even the nucleotides of the Chernobyl dogs, and found no abnormalities indicative of radiation-induced mutation.

To establish a baseline for comparison, the team compared the genome of Chernobyl City dogs located 10 miles from the CEZ to dogs found in regions of Russia, Poland, and other nearby countries. Once they determined that the populations were genetically similar, they then used the Chernobyl City dogs as a representative control for their study. Of course, the task wasn’t simple, as more than a couple dozen dog generations have past since the original pups that witnessed to the Chernobyl meltdown in 1986.

“We know that, for example, exposure to high doses of radiation can introduce instability from the chromosomal level on down,” Matthew Breen, senior author of the study from North Carolina State University, said in a press statement. “While this dog population is 30 or more generations removed from the one present during the 1986 disaster, mutations would likely still be detectable if they conferred a survival advantage to those original dogs. But we didn’t find any such evidence in these dogs.”

That said, the 2023 study still provides a template for further investigation into the effects of radiation on larger mammals, as the DNA of dogs roaming the Chernobyl Power Plant and nearby Chernobyl City can be compared to dogs living in non-irradiated areas. Despite a current lack of firm conclusions, the study has shown once again that an area that—by all rights—should be a wasteland has become an unparalleled scientific opportunity to understand radiation and its impact on natural evolution.