By Stephen Beech
The remains of a 14,400-year-old woolly rhinoceros recovered from an Ice Age wolf’s stomach have given new clues about the demise of the species.
Analysis of the rhino’s genome suggests the extinct animal was wiped out by climate change rather than by human hunters, say scientists.
It is the first time the entire genome of an Ice Age creature found in the stomach of another species has ever been sequenced.
The genome was recovered from a tissue sample found preserved inside the stomach of an ancient wolf in Russia’s Siberia region.
The findings, published in the journal Genome Biology and Evolution, show that woolly rhinos remained “genetically healthy” until the end of the last Ice Age.
Scientists say the species therefore probably died out due to a rapid collapse of the population, rather than a slow demographic decline.
The work was conducted by researchers at The Centre for Palaeogenetics, a collaboration between Stockholm University in Sweden, and the Swedish Museum of Natural History.
Study co-author Camilo Chacón-Duque said: “Sequencing the entire genome of an Ice Age animal found in the stomach of another animal has never been done before.
“Recovering genomes from individuals that lived right before extinction is challenging, but it can provide important clues on what caused the species to disappear, which may also be relevant for the conservation of endangered species today.”
He explained that the analyzed rhino sample came from the frozen remains of an Ice Age wolf discovered in permafrost near the village of Tumat in north-eastern Siberia.
When an autopsy was conducted on the wolf, researchers identified a small fragment of preserved tissue in its stomach.
Radiocarbon dating revealed the tissue to be around 14,400 years old, and DNA sequencing identified it as a woolly rhinoceros – one of the youngest specimens of woolly rhinoceros ever discovered.
The research team explained that mapping the genome from that type of material is “extremely difficult” as ancient DNA is usually degraded and occurs in very small amounts, and the presence of predator DNA further complicates the analysis.
Study lead author Sólveig Guðjónsdóttir, who conducted the work as part of her master’s thesis at Stockholm University, said: “It was really exciting, but also very challenging, to extract a complete genome from such an unusual sample.”
The researchers compared the Tumat rhinoceros’ genome with two other high-quality genomes from older specimens, dated to around 18,000 and 49,000 years ago, respectively.
The comparisons allowed the team to examine how genome diversity, inbreeding levels, and the number of harmful mutations changed through time during the last Ice Age.
They found no signs of genetic deterioration as the species approached extinction.
The team say that indicates that the woolly rhino probably maintained a “stable and relatively large” population until just before the species disappeared.
Team member Dr. Edana Lord said: “Our analyses showed a surprisingly stable genetic pattern with no change in inbreeding levels through tens of thousands of years prior to the extinction of woolly rhinos.”
The researchers found no signs in the genome that would indicate a long-term gradual population decline.
They say the extinction therefore appears to have occurred relatively quickly, probably caused by global warming at the end of the Ice Age.
Dr. Love Dalén, Professor of evolutionary genomics at the Centre for Palaeogenetics, added: “Our results show that the woolly rhinos had a viable population for 15,000 years after the first humans arrived in north-eastern Siberia, which suggests that climate warming rather than human hunting caused the extinction.”
