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For decades, scientists have studied animals living in or near the Chernobyl nuclear power plant to see how increased levels of radiation affect their health, growth and development.
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One study analyzed the DNA of 302 wild dogs living near the power plant, compared the animals to others living 10 miles away, and found remarkable differences.
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While the study does not prove that radiation is the cause of these differences, the data provide an important first step in analyzing these irradiated populations and understanding how they compare to dogs living elsewhere.
On April 26, 1986, the Chernobyl nuclear reactor in northern Ukraine—then part of the Soviet Union—exploded, sending a massive wave of radiation into the sky. Nearly four decades later, the Chernobyl power plant and many parts of the surrounding area remain uninhabited, at least by humans.
Animals of all kinds have thrived in the absence of humanity. Amidst the radiation-resistant fauna live thousands of feral dogs, many of which are descendants of pets left behind in the rapid evacuation of the area many years ago. As the world’s worst nuclear disaster approaches its 40th anniversary, biologists are now taking a closer look at animals located in the Chernobyl exclusion zone (CEZ), which is roughly the size of Yosemite National Park, and investigating how decades of radiation exposure may have altered the animals’ genomes — and possibly even accelerated evolution.
Scientists from the University of South Carolina and the National Human Genome Research Institute began examining the DNA of 302 wild dogs found in or around the CEZ to better understand how radiation may have altered their genomes. Their results were published in the journal Advances in science in 2023.
“Do they have mutations that they have acquired that allow them to live and breed successfully in this region?” co-author Elaine Ostrander, an expert in dog genomics at the National Human Genome Research Institute, said The New York Times. “What challenges do they face and how have they coped genetically?”
The idea that radiation accelerates natural evolution is not new. The practice of deliberately irradiating seeds in outer space to induce advantageous mutations, for example, is now a well-used method for developing crops that are suitable for a warming world.
Scientists have looked at certain animals living in the CEZ for years, including bacteria, rodents and even birds. A 2016 study found that Eastern tree frogs (Hyla from the east), which are usually green, were more frequently black within the CEZ. 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 got scientists thinking: Could something similar be happening to the wild dogs in Chernobyl?
The study found that wild dogs living near the Chernobyl power plant showed distinct genetic differences from dogs living just 10 miles away in the nearby city of Chernobyl. While this may seem to heavily imply that these dogs underwent some type of mutation or rapid evolution due to radiation exposure, this study is only a first step in proving this hypothesis.
However, an environmental scientist, speaking with Science Newssays these studies can be a tricky business, in large part because disentangling radiation-induced mutations from other effects, such as inbreeding, is incredibly difficult.
And in the time since the original study was published, other researchers have dug into the question and come up with competing results. In fact, a study published nearly two years later confidently states that we can remove radiation from the list of explanations for the current state of the Chernobyl canine population. Published in journal PLOS One by scientists at North Carolina State University and Columbia University Mailman School of Public Health in New York, this new genetic analysis looked at the chromosome level, the genome level and even the nucleotides of the Chernobyl dogs and found no abnormalities indicating radiation-induced mutation.
To establish a baseline for comparison, the team compared the genomes of dogs from the city of Chernobyl located 10 miles from the CEZ with dogs found in nearby regions of Russia, Poland and other countries. Once they determined that the populations were genetically similar, they then used the dogs from the city of Chernobyl as a representative control for their study. Of course, the task was not simple, as more than a few dozen generations of dogs have passed since the original puppies that witnessed the Chernobyl meltdown in 1986.
“We know that, for example, exposure to high doses of radiation can introduce instability from the chromosomal level down,” said Matthew Breen, lead author of the study at North Carolina State University, in a press statement. “While this population of dogs is 30 or more generations removed from that present during the 1986 disaster, the mutations would likely still be detectable if they conferred a survival advantage on those original dogs. But we found no such evidence in these dogs.”
That said, the 2023 study provides yet another template for further investigation of the effects of radiation on larger mammals, as the DNA of dogs roaming the Chernobyl power plant and the nearby city of Chernobyl can be compared to dogs living in non-irradiated areas. Despite the 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.
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