Two ancient wolf cubs, discovered buried in the Siberian permafrost over a decade ago, are now shedding new light on their past through rich DNA evidence hidden in their remains.
For the first time, researchers have uncovered a piece of woolly rhino meat—an animal comparable in size to modern white rhinos but with a thick furry coat—preserved in the stomach of one of the wolf puppies. The DNA from this meat and fur has remarkably survived for over 14,000 years under the ice, enabling scientists to sequence the entire genome. They published their findings in the Wednesday Journal “Genome Biology and Evolution”.
“This is the first instance where an entire genome has been reconstructed from an Ice Age animal found within another Ice Age animal,” stated study author Camilo Chacón-Duque, an evolutionary biologist from Uppsala University in Sweden. “The genome quality is exceptional and of high resolution.”
The woolly rhinoceros in question went extinct approximately 14,400 years ago, just a few hundred years prior to its disappearance from the fossil record. This gives researchers a unique glimpse into the genome of a species on the brink of extinction.
“This sample represents the youngest woolly rhinoceros ever sequenced, marking the closest proximity of the species to extinction,” Chacon-Duque noted.
Evolutionary biologists have long debated whether it was human hunters or climate change that ultimately led to the woolly rhinoceros’s extinction. New genomic data indicates that the population may have been robust until its sudden decline.
The first of the two small puppies was discovered by ivory hunters searching for mammoth tusks in Siberia nearly 15 years ago, with the other being found four years later.
These mummified animals, known as the “Tumat pups,” have unexpectedly aided scientists in exploring the fate of another species.
According to the research, both puppies were female and likely littermates, found just six feet apart and sharing several DNA traits, as noted in a study published in Quaternary Research magazine last year.
“They died at a young age, around nine weeks,” explained Anne-Catherine Wyborg Runge, co-author of the Quaternary research paper. “At that age, they still had their baby teeth.”
Initial studies suggested that thawing permafrost may have triggered landslides, entombing the wolves in ice and snow, although it’s also possible that the puppies perished due to a collapsing burrow.
“They would have been buried instantly and then frozen for 14,000 years,” noted Runge’s co-author Nathan Wales, a senior archaeology lecturer at the University of York, UK.
Interestingly, the puppies were discovered near where ancient humans hunted woolly mammoths, suggesting they might have been domesticated dogs rather than wild wolves. However, no mammoth DNA was found in the pup’s stomach. Researchers believe one pup’s last meal was woolly rhinoceros meat, while the other had recently eaten a bird, leaving behind rhino meat and some feathers in the permafrost.
In a recent study published Wednesday, Chacón-Duque sequenced resilient chunks of meat from the animal’s last meal.
“This piece had remained in the pup’s stomach for years. It’s truly remarkable,” Runge remarked.
Although complete woolly rhinoceros genomes are rare, researchers compared their findings with two other high-quality genomes from rhinos that went extinct approximately 18,000 and 49,000 years ago.
Chacón-Duque and team detected no signs of inbreeding or harmful mutations within the population, indicating it was robust.
“They haven’t identified any indicators suggesting population collapse, which is peculiar considering the species went extinct,” noted Wales, an ancient DNA expert not involved in the study.
Several centuries after the woolly rhinoceros roamed these areas, a significant warming phase commenced in the Northern Hemisphere, marking the end of the Ice Age. Study authors believe this newly sequenced DNA supports the hypothesis that climate change contributed to the woolly rhino’s extinction.
Chacón-Duque posits that the rising temperatures likely exert stress on cold-adapted populations, and human expansion could have facilitated the spread of diseases affecting the woolly rhino.
“All these factors likely interacted synergistically, contributing to the species’ ultimate demise,” Chacón-Duque concluded. “Without a doubt, climate change played a significant role.”
Mick Westbury, an associate professor and expert on ancient rhinos from the Technical University of Denmark, agrees with the theory’s plausibility.
However, Westbury points out that rare ancient DNA can pose interpretation challenges and that generational changes can heavily impact a species’ genetics. The woolly rhinoceros may have been at risk even if genetic analyses did not immediately indicate it.
“Sometimes, genomics alone doesn’t provide the complete picture,” Westbury remarked.
Nonetheless, Westbury suggests that these findings could offer vital insights for conservation efforts as human-induced climate change becomes an increasing threat to existing species.
“Our results indicate that the woolly rhino does not appear to be on the brink of extinction,” Westbury noted. “A species may seem genetically viable on the surface but still face vulnerabilities.”
Source: www.nbcnews.com
