The Wrangel Island woolly mammoth descended from a very small population and survived for 6,000 years despite genetic obstacles. Its sudden extinction remains a mystery and offers lessons for modern conservation efforts. Photo by Beth Zaiken
Genetic analysis of the last woolly mammoths on Wrangel Island reveals a population that has survived for 6,000 years despite severe inbreeding and low genetic diversity.
Starting with fewer than eight individuals, the group grew to 200-300. While genetic issues did not directly cause their extinction, it is unclear what ultimately wiped them out. This study provides insight into how populations like this can inform current conservation strategies for endangered species. seed today.
The last remaining population of mammoths became isolated on Wrangel Island, off the coast of Siberia, 10,000 years ago when rising sea levels cut off the mountainous island from the mainland. Over the next 6,000 years, this isolated population lived on the island, starting with fewer than eight animals and growing to 200 to 300 within 20 generations, according to a new genomic study. cell On June 27, a study showed that the Wrangel Island mammoths showed signs of inbreeding and low genetic diversity, but these factors alone cannot explain the mammoths’ mysterious eventual extinction.
![Siberian mainland tusks](https://scitechdaily.com/images/Siberian-Mainland-Tusk-777x577.jpg)
Tusk from mainland Siberia. Credit: Love Dalén
Reassessing extinction theory
“We can now confidently reject the idea that their populations were so small that they were destined to go extinct for genetic reasons,” says lead author Love Dalen, an evolutionary geneticist at the Centre for Paleogenetics, a joint institute of the Swedish Museum of Natural History and Stockholm University. “This means that it was probably some kind of chance event that caused the mammoths to go extinct, and without that chance event, mammoths would still be alive today.”
![Love Darren](https://scitechdaily.com/images/Love-Dalen-1-777x518.jpg)
Love Darren. Credit: Ian Watts
Insights into current conservation efforts
This analysis of the Wrangel Island mammoths not only sheds light on the population dynamics of these animals, but may also help develop conservation strategies for the currently endangered animals.
“The mammoth is an excellent system for understanding the ongoing biodiversity crisis and what happens from a genetic perspective when a species experiences a population bottleneck, because it reflects the fate of many modern populations,” says lead author Marianne DeHask from the Centre for Paleogenetics.
![Marianne DeHask Ancient DNA Institute](https://scitechdaily.com/images/Marianne-Dehasque-Ancient-DNA-Lab-1-777x583.jpg)
Marianne DeHask working at the Ancient DNA Laboratory. Photo by Love Darren.
Genetic challenges and lasting legacies
To understand the genomic impact of the Wrangel Island bottleneck on the mammoth population, the team analyzed the genomes of 21 woolly mammoths: 14 from Wrangel Island and seven from the mainland population that lived before the bottleneck. In total, the samples span the last 50,000 years of the woolly mammoth’s lifespan, providing insight into how the mammoth’s genetic diversity has changed over time.
Compared to their mainland ancestors, the genomes of the Wrangel Island mammoths showed signs of inbreeding and lower genetic diversity. In addition to lower overall genetic diversity, there was also reduced diversity in the major histocompatibility complex, a group of genes known to play an important role in vertebrate immune responses.
![Wrangel Island Fang](https://scitechdaily.com/images/Wrangel-Island-Tusk-777x518.jpg)
Fangs from Wrangel Island. Credit: Love Dalén
Long-term genetic effects and future research
The researchers showed that throughout the 6,000 years that mammoths inhabited Wrangel Island, the population’s genetic diversity continued to decline, albeit at a very slow pace, suggesting that the population size remained stable until the end. The researchers also showed that while the island’s mammoth population gradually accumulated moderately deleterious mutations throughout its 6,000-year existence, the population slowly eliminated the most deleterious mutations.
“While highly deleterious mutations in individuals are essentially unsurvivable, and so these mutations gradually disappeared from populations over time, we know that mammoths accumulated mildly deleterious mutations right up until their extinction,” DeHask said. “It’s important to remember that current conservation programs won’t be enough to simply grow populations back to a healthy size again; they also need to be actively and genetically monitored, as these genomic effects can last for more than 6,000 years.”
The final mystery of the mammoth’s extinction
The mammoth genome analyzed in this study spans a long period of time, but doesn’t include the last 300 years of the species’ existence, but the researchers have unearthed fossils from that final period of the mammoth, which they plan to sequence in the future.
“What happened to them at the end is still a mystery – we don’t know why they went extinct after surviving pretty well for 6,000 years, but we think it was probably a sudden event,” Dallen says. “We think there’s still hope we can figure out why they went extinct, but we can’t make any promises.”
Reference: “Temporal dynamics of mammoth genome erosion before extinction,” June 27, 2024, cell.
Publication number: 10.1016/j.cell.2024.05.033