The world’s worst nuclear disaster didn’t just affect humans. When the Chernobyl nuclear power plant experienced a catastrophic explosion on April 26, 1986, radioactive fallout forced Soviet authorities to abandon the area, declaring a giant exclusion zone covering some 2,600 square kilometers (1,000 square miles). Since then, studies have shown that animals came to thrive in the abandoned Chernobyl Exclusion Zone (CEZ), free from interference from living humans. populations. At the time of evacuation, many residents were forced to leave their pets behind, and ‘liquidators’ were subsequently sent to destroy the remaining animals, along with livestock in the contaminated area. But many animals survived the purge. “It is unclear how many animals were able to evade the liquidators, but enough domestic dogs escaped this fate to establish persistent populations within the area,” the researchers explain in a new paper in Genes, led by first author and North Carolina State population geneticist Megan Dillon. University.”It is estimated that several hundred dogs currently inhabit the ZEC and are believed to be descended, at least in part, from the pets left behind after the disaster.”A stray dog in the radioactive zone. (Sergiy Romanyuk/Getty Images) These dogs, more than 30 canine generations removed from the disaster, offer a unique opportunity to study how decades of pollution could affect living organisms and their evolution. In a study published in 2023, some members of the same research team analyzed the dogs and found that dogs living near the site of the abandoned nuclear power plant were genetically distinct from dogs living further away, leaving open the possibility that genetic variations could be the result of mutations caused by persistent radiation. A follow-up study in 2024 found no evidence that the mutations were driving the genetic differentiations, so Dillon and his fellow researchers continued investigating, in an attempt to solve the mystery. [new study] “It ties up some of the loose ends from our previous work, where in characterizing the genetic structure of the population we found that while these two groups of dogs are very close geographically, they have a very high degree of genetic difference, and those differences are not due to mutation,” Dillon says. “With this work we wanted to explore two additional evolutionary drivers on a larger scale: Are genetic differences due to selection or are they due to genetic drift over time in an isolated population?” In the new research, Dillon and his team analyzed the entire genome sequence. Data collected from 106 dogs between 2018 and 2019, including animals from the nuclear power plant (NPP) and the city of Chernobyl (the Ukrainian spelling of Chernobyl), approximately 16 kilometers (10 miles) away. Chernobyl dogs living outside the New Safe Confinement Structure, which was built to contain radioactivity from the reactor four explosion (Clean Futures Fund+) if mutations are not responsible for the genetic differences seen in dogs living at the nuclear power plant. plant, natural selection could be one explanation, since existing genetic variants become more common if they improve an organism’s chances of surviving and reproducing in a particular environment. Alternatively, it is possible that genetic drift could explain the result, in which genetic changes occur randomly, without necessarily conferring any survival advantage. However, in the case of dogs living near the nuclear power plant, the differentiation does not appear to be due solely to chance. The researchers found evidence of concentrated changes in specific genomic regions located near genes associated with cancer, cellular function and maintenance, infectious diseases, and immune response. “While we can’t say with certainty whether what we’ve found can be directly confirmed as selection, we do find that these genomic signatures suggest selection,” Dillon says. “When we drilled down into those genomic regions, we found that these genes are involved in biologically relevant pathways that could allow them to overcome the effects of exposure to toxic substances in this environment.” Additionally, researchers believe it is possible that after the disaster, some dogs may have had genetic advantages that protected them from cancer or provided them with better immune responses or resistance to toxic exposures. Over time, such dogs may have conferred survival advantages on their offspring, as does each successive generation, in a mode of natural selection called directional selection. “Some consequence of living in that environment,” says geneticist Matthew Breen of North Carolina State University. “But what we’re saying is that the consequence may not have gone as far as changing the dogs’ genome to adapt; it could be those that were able to survive the initial exposures that had this level of underlying genetic diversity and variants to offer a higher degree of fitness.” Disaster of 1986, when Ukraine was part of the Soviet Union and Russian transliterations were widely used. The Ukrainian spelling is “Chornobyl”. This article was fact-checked by Rebecca Dyer and edited by Rebecca Dyer. While we take pride in our process, we are human. If you spot an error, please let us know.
