Chernobyl’s Stray Dogs Show Signs of Selection, Not Radiation Damage

Dogs living around the Chernobyl nuclear power plant are genetically distinct from dogs just a few miles away, and a new study suggests the reason may be natural selection rather than radiation-induced mutations, ScienceAlert reported. The researchers stress that they cannot yet confirm selection directly.

The work, published in the journal Genes, was led by population geneticist Megan Dillon of North Carolina State University. It builds on two earlier studies of the same animals and tries to explain why two neighboring groups of dogs differ so much in their DNA.

The study in six numbers

• April 26, 1986: the date of the explosion at the Chernobyl plant. Fallout forced Soviet authorities to abandon the area and declare an exclusion zone.
• About 2,600 square kilometers (1,000 square miles): the size of that exclusion zone, which ScienceAlert says later became a refuge where animals thrived without people.
• Several hundred: the estimated number of dogs now living in the zone. The researchers believe they descend, at least in part, from pets left behind during the evacuation.
• More than 30: the number of canine generations separating today’s dogs from the disaster.
• 106: the number of dogs whose whole-genome sequence data were analyzed, collected between 2018 and 2019 from animals at the power plant and in Chornobyl City.
• About 16 kilometers (10 miles): the distance between the plant and Chornobyl City, the two places the dogs came from.

What is behind the numbers

After the evacuation, many residents had to leave their pets behind, and so-called liquidators were sent to destroy the remaining animals in the contaminated area. Many animals survived anyway. The researchers write that enough domestic dogs escaped to establish lasting populations in the zone.

A 2023 study by some of the same team found that dogs near the plant were genetically different from dogs living farther away. That left open the idea that lingering radiation had caused the differences through mutations. A 2024 follow-up found no evidence that mutations were driving the split.

The new paper tests two other explanations. One is natural selection, in which existing genetic variants become more common because they help animals survive and reproduce in a given environment. The other is genetic drift, in which changes happen at random in an isolated population and give no particular advantage.

According to ScienceAlert, the pattern in the plant dogs does not look like chance alone. The team found changes concentrated in specific regions of the genome near genes linked to cancer, cellular function and maintenance, infectious diseases and immune response. Dillon said the team cannot say for certain that this is selection, but the signatures are suggestive of it.

The researchers think it is plausible that, after the disaster, some dogs already carried genetic advantages that protected them from cancer, strengthened their immune response or helped them resist toxic exposures. Those dogs could then have passed the advantages to their offspring, generation after generation, in a process called directional selection. The team says future research will have to test that idea.

Why it matters

The finding changes the question people often ask about Chernobyl’s animals. Many assume that living in a contaminated place must have rewritten the dogs’ DNA. Matthew Breen, a geneticist at North Carolina State University, said the consequence may not have gone as far as changing the dogs’ genome to adapt. Instead, he said, the dogs that survived the first exposures may have started with enough underlying genetic diversity to be fitter than others.

In other words, the dogs may not have been transformed by the zone. The zone may have favored certain dogs that were already there. Because the dogs are more than 30 generations removed from the disaster, they give scientists a rare chance to study how decades of contamination can affect living organisms and their evolution.

The result is a single study based on genome data from 106 dogs, and the authors describe it as suggestive rather than conclusive. It does not show that the dogs are healthier or sicker than other dogs, and it says nothing about what long-term exposure would mean for people.

Around Prague, based on reporting by ScienceAlert