The researchers also don’t have access to longitudinal samples that would show exactly how this population has changed over time. “It’s almost like looking at a single still image and trying to figure out what came before it,” said Matthew Breen, a professor of genomics at North Carolina State University and the study’s senior author. “Those first few years were probably the most critical period—if they were selected, that’s when that selection process would have happened.”

It’s not possible to go back and get samples from the dogs who lived there in 1986, a time when no organism—not even a bacterium—had its full genome sequenced. Breen was a graduate student in England then. “I was involved in a project driving around the Welsh mountain hills, collecting sheep from the pastures because the radioactive cloud had blown over Western Europe,” he recalled. There wasn’t anything to see in the data gathered then, but the technology has evolved, and those sheep had also not been living at the center of a nuclear meltdown for generations.

Nearly four decades after the accident, the Chernobyl exclusion zone has also become a refuge for wildlife. Wolves, deer, wild boars, and lynx now roam the area—a return that researchers largely attribute to the decline in human activity. Among some of these residents, such as the wolf population, researchers have also observed similar genomic distinctions to those seen in the dogs.

“It really demonstrates the resilience of nature to catastrophic events caused by humans,” Breen said. “You push something in one direction, it can respond to that and either push back or deviate its path going forward. I think this is what we’re seeing here.”

This story originally appeared on WIRED en Español and has been translated from Spanish.

Additional reporting from Anna Rogers.