A 57,000-year-old wolf puppy found frozen in the Yukon permafrost

In the summer of 2016, a gold miner from the Canadian territory of the Yukon found an unexpected treasure. As he tossed a wall of permafrost with a cannon of water to release any wealth that might be found inside, Neil Loveless saw something melting from the ice. It was not a precious mineral, but the oldest and most complete wolf mummy ever discovered.

Loveless quickly put the frozen chicken in a freezer until paleontologists could take a look. They found that the well-preserved animal was a juvenile female, part of an extinct ecosystem dating back to the time when northwestern Canada hosted American mastodons and other Pleistocene megafauna. The local people called Tr’ondëk Hwëch’in the 57,000-year-old chick Zhur, meaning “wolf” in the language of their community.

Exceptional mammals have been recovered from the Siberian tundra dating back to the Pleistocene, a period of about 2.6 million to 11,700 years ago, sometimes called the ice age, because the ice caps on the poles were much larger than today. . However, finding such an intact wolf in the Yukon is unprecedented.

Just seven weeks after his death, the young gray wolf belonged to a population that first arrived in the Yukon region migrating from Siberia over the Bering land bridge.

“In Siberia, such conservation is quite common because of the way permafrost keeps things there, which is much less common in the Yukon, Alaska and other parts of North America,” says Julie Meachen, a paleontologist at the University. Des Moines. lead author of a study describing Zhur published today in the journal Current biology. Much of the Zhur remained intact after tens of thousands of years, from the fur of the coat to the delicate papillae on the tongue.

“Conservation looks amazing,” says University of Copenhagen paleontologist Ross Barnett, who was not involved in the study. But there is more to Zhur than meets the eye. “It tells us a lot,” says Meachen, from her age to death – seven weeks – to what she ate. The research provides an insight into a period of respite between frozen expanses of Earth’s history.

A population of lost wolves

Zhur lived during an interglacial period, when vast Arctic glaciers temporarily retreated and forests overcame colder meadows. These were the days of mastodons, camels, giant beavers, and, as Zhur documents, of gray wolves.

“Having such an extraordinary conservation of a carnivore is a unique situation to look at glacier ecosystems from the point of view of predators,” says Tyler Murchie, a paleogeneticist at McMaster University who was not involved in the study.

An illustration of a gray wolf hunting fish with its young in northwestern Canada nearly 60,000 years ago.

Although they are iconic parts of the modern North American wilderness, gray wolves have not evolved in America. These canids first appeared in Eurasia and crossed the Bering Earth Bridge in the late Pleistocene, more than 500,000 years ago.

“Zhur comes from a time that isn’t very well known in the Yukon when it comes to mummies,” says Barnett. And examining the remains of wolf cub DNA, Meachen and colleagues found that this animal documents a group of wolves that no longer exist in the region.

Zhur belonged to a population that had genetic ties to wolves in both Alaska and Eurasia, but wolves living in the Yukon today have a different genetic signature. The findings suggest that the first gray wolves in the Yukon were wiped out and later replaced by other populations that had already made their way south.

The amazing conservation of Zhur wolf cubs allows scientists to study both the animal’s physical features and its DNA.

“Ancient DNA repeatedly demonstrates how much more complex evolutionary histories and paleoecology are than would otherwise be obtained from bone and fossil studies,” says Murchie. Without Zhur’s genes, this removal and replacement would have been invisible to scientists.

A shortened prehistoric life

Zhur’s body also tells us about her life. At just seven weeks old when he died, the chick had just passed the age of weaning, when he would start eating more solid foods. The geochemical signatures on her teeth indicate that she lived with river meals and streams, probably fish such as Chinook salmon that still appear in the nearby rivers where she was found. Many modern wolves in northern Alaska have a similar diet, which approaches fish more often than large game.

Unfortunately, Zhur’s life was shortened. She appears to have died in a crash, with rapid burial facilitating the exceptional preservation of her body. Other mammals from this period – such as arctic squirrels and black-footed ferrets – have been kept in the same way.

Zhur existed at ancient intersections, not only between cold glacial periods, but between wolf populations that are now separated. By studying the genes of chicks, scientists can gain a better understanding of their place in the ancient world and what has changed since then. “Ancient DNA brings to life the dynamism of the late Pleistocene, which was largely invisible only from the bones,” says Barnett.

The way animal populations have moved over time Pleistocene it is a story that is still teased from the reins of ancient DNA left in the preserved specimens, but Zhur’s remains provide important clues. Where bones and genes meet, researchers gain a new window into the lost worlds of the ice age.