The 1986 Chernobyl disaster was the worst nuclear meltdown in history. Today, much of the area around the old plant in Ukraine and bordering Belarus remains uninhabited, including the town of the same name and Pripyat. But this is only true if we are talking about people.
Many animals still live in the area. In many cases, wildlife populations have flourished due to the lack of human presence for more than 35 years. But does this mean that the animals that live in the area have adapted to the unique threats they face from the radiation in the area?
Some research suggests that populations in the Chernobyl Exclusion Zone have begun to develop. Other researchers believe that there is not yet enough rigorous data to prove any kind of adaptive effect.
“We’re doing the best we can with the resources we have right now,” said Tim Musso, a biologist at the University of South Carolina who has tracked the evolution of radiation-induced evolution for many years.
The Frogs of Chernobyl: Evolution in Action
In 2016, researchers Pablo Buraco and German Orizaola began studying how eastern tree frogs respond to radiation in the Chernobyl area. Although usually bright green, these frogs are sometimes black.
However, they found in the Chernobyl area a lot frogs showing the uncharacteristic black coloration.
Melanin, responsible for this dark color in various species, can actually mitigate some of the negative effects of UV radiation. In humans, e.g. dark pigmentation can protect from some of the negative effects of too much sunlight. Melanin also protects against some radiation-related cellular damage.
Burraco and Orizaola expanded their study in subsequent years by analyzing the skin color of frogs caught from 12 lakes in northern Ukraine — including some in the most radioactive parts of the Chernobyl area. They compared them to frogs from other lakes outside the Chernobyl Exclusion Zone, which have relatively low levels of radiation.
In total, the researchers analyzed more than 200 frogs and found that those from high-radiation areas were, on average, much darker.
“Chernobyl frogs may have undergone a process of rapid evolution in response to radiation,” they reported in The conversation. They say this is likely the result of natural selection: darker frogs survived in relatively higher proportions than their green counterparts.
Read more: Glass frogs become translucent, hiding their blood
Mutated animals in Chernobyl
Also in 2016 Musso and colleague published a review examining 17 cases where researchers claim to have found adaptations to radiation at Fukushima and Chernobyl. These include everything from pine trees to grasshoppers and voles.
However, the researchers failed to find strong evidence of adaptation in most of these studies, other than the eradication of a few individuals who appeared to be genetically more vulnerable to the effects of radiation.
Many of the studies reviewed included relatively small sample sizes of single contaminated sites and single control sites. Or they haven’t been conducted with “substantial rigor” to support the evolutionary adaptation hypothesis, Musso says.
There was one exception: the researchers latched on to bacteria from barn swallow feathers in highly irradiated parts of Chernobyl, as well as bacteria from Denmark with normal levels of radiation. They found that the bacteria of the Chernobyl swallows were more resistant to damage caused by the induced radiation.
This is not to say that Musso ruled out evolution entirely. “I’m as guilty as anyone else[one] to speculate on it,” he says. In fact, researchers have proven in several cases that evolution is only possible within a few generations. Musso simply believes that the studies so far have not been rigorous enough to support the idea.
Read more: How long will Fukushima remain radioactive?
Chernobyl dogs
Feral dogs have also been running amok in Chernobyl for over 35 years. Many are the descendants of pets left behind during the evacuation of the area. “People weren’t given much time,” says Elaine Ostrander, a geneticist at the National Institutes of Health.
In total, there may be thousands of feral dogs in the Chernobyl Exclusion Zone – their populations are likely boosted by food given by tourists who are coming in increasing numbers to the area.
Musso and his colleagues contacted Ostrander and others to learn more about the genetic profile of these dogs; in a study recently published in Scientific progressthey analyzed DNA samples from 15 generations of wild dogs in Chernobyl.
“We were interested in identifying variants in the DNA sequences that allowed these dogs to live and reproduce,” says Ostrander.
Their analysis revealed that different populations of dogs in the area had different signatures that identified where they came from. Those from the city of Chernobyl, for example, had a signature that was different from those at Pripyat, just 9 miles away. They also compared them to the genetic profiles of dogs that live in nearby Poland and elsewhere in Eastern Europe.
Doggone Radiation
The level of genetic detail the researchers examined in these dogs is unique, Musso says. But this research is only the first step.
Now that the genetic profiles of different Chernobyl dog populations have been characterized, researchers can begin to investigate whether there are common genetic threads between Pripyat and Chernobyl dogs that differ, for example, from dog populations living with lower levels of radiation.
This kind of research may finally reveal how an animal that is relatively similar to humans responds and develops to radiation.
“[Its] “However, the greatest potential,” the study’s authors wrote, “lies in understanding the biological basis of animal and ultimately human survival in regions of intense and continuous environmental assault.”
Read more: The science behind dog DNA testing