Feral dogs living near Chernobyl differ genetically from their ancestors who survived the 1986 nuclear plant disaster—but these variations do not appear to stem from radioactivity-induced mutations. The new findings are helping experts contextualize how such ecological catastrophes influence the environment around them, and how these effects ripple out over time.
Chernobyl’s reactor meltdown remains history’s worst nuclear disaster. The initial explosion killed two facility workers on April 26, 1986, but at least another 28 people succumbed to acute radiation poisoning and associated issues over the next three months. At least 9,000 cancer-related fatalities across Ukraine, Belarus, and Russia occurred in the decades since the meltdown, and a roughly 1,000-square-mile exclusion zone still exists around the facility that includes the abandoned town of Pripyat. In addition to the confirmed deaths, other longterm effects suggested by multiple studies include contaminated water, damage to plantlife, and birth defects in both humans and animals.
The ecological damage remains difficult to comprehend, but the region never became completely devoid of life. Many animals survived even after undergoing radiation-based genetic mutations—notably, a number of pet dogs abandoned by their owners during Chernobyl’s hasty evacuation orders. Today, several hundred feral dogs are estimated to live in the area, presenting a unique opportunity to study how these populations adapt to immense and sudden environmental degradation.
[ Related: Without humans, what would happen to life on Earth? ]
In a study published last year, researchers identified stark genetic differences between the Exclusion Zone’s feral dogs and dogs living barely 10 miles away in Chernobyl City. These included 391 genetic outlier regions between the two populations, some specifically associated with DNA repair. But according to their follow-up investigation published in the journal PLOS One, the team now says there is “no evidence” that these contrasts are the result of an increased mutation rate.
The researchers reached their conclusion after analyzing samples at the chromosomal level, followed by small genome intervals and differences between individual nucleotides. They were particularly on the hunt for evidence of abnormalities such as accumulated germ line DNA mutations—alterations in reproductive cell DNA passed from parents to offspring over multiple generations. Matthew Breen, an NC State professor of comparative oncology genetics and study corresponding author, likened the overall process to using your phone camera’s zoom function.
“[W]e start with a wide view of a subject and then zoom in,” Breen said in an accompanying statement on January 13th. “We know that, for example, exposure to high doses of radiation can introduce instability from the chromosomal level on down.”
Breen noted that while the current dog population is more than 30 generations removed from the Chernobyl disaster in 1986, the team would likely still identify genetic mutations if, for example, they provided some form of survival advantage. Researchers, however, found no evidence of such abnormalities.
“[M]utation does not appear to be the cause of the previously identified genetic differentiation between these two geographically close populations of free-breeding dogs,” the study authors conclude. “Considering this, in conjunction with the previous work on breed composition, inbreeding, and comparisons to other free-breeding dog populations, we have yet to identify the definitive cause for this genetic differentiation.”
Megan Dillon, an NC State PhD candidate and study lead author, believes the first generation of dogs who survived Chernobyl may have done so thanks to certain genetic traits they already possessed—not those conferred through radioactive mutation.
“So perhaps there was extreme selective pressure at the start, and then the dogs at the power plant just remained separate from the city population,” she said. “Investigating that question is an important next step that we are now working on.”
Their latest findings extend far beyond dogs, as well. Given the number of canine generations that have lived since the nuclear meltdown, Dillon likened the present-day population to humans “centuries removed from the [those] present at the time of the disaster.”
But just because today’s Chernobyl dogs lack genetic mutations from radioactive fallout doesn’t mean they—or the people still working on cleanup efforts—are safe from health issues.
“Most people think of the Chernobyl nuclear accident as a radiological disaster in an abandoned corner of Ukraine, but the potential adverse health implications are much wider,” added Norman Kleiman, study co-author and a professor of environmental health sciences at Columbia University School of Public Health.
Kleiman explained that, in addition to radiation, other toxins such as lead powder, pesticides, asbestos, and heavy metals have been released into the environment over three decades of remediation work undertaken by thousands of people.
“The importance of continuing to study the environmental health aspects of large-scale disasters like this cannot be overemphasized,” said Kleiman.
