How did the woolly mammoth, an ambassador of the Ice Age, come to be trapped in modern-day Wrangel? … [+]
Rising sea levels around 10,000 years ago transformed Wrangel Island into a last refuge for the woolly mammoths, isolating them from their mainland counterparts. As the Earth’s climate continued to warm and habitats changed, Wrangel Island became one of the last viable environments for these mammoths to survive, setting the stage for their final chapter.
Four millennia ago, Wrangel Island was a frozen haven, the last glacier home to woolly mammoths … [+]
A common theory for the extinction of isolated populations such as the woolly mammoths on Wrangel Island often points to inbreeding. Inbreeding can reduce the genetic variability of a population and increase the spread of harmful genetic mutations, leading to lower survival and reproductive rates. A notable example is the Tasmanian tiger, or thylacine, which suffered from reduced genetic diversity due to severe inbreeding before becoming extinct in the 20th century.
However, this popular theory that inbreeding leads to extinction may not apply to the Wrangel Island woolly mammoths, according to a paper published in June 2024 in Cell.
There was a ‘bottleneck’ event, but the Mammoth was well on its way to recovery
The study analyzed 21 genomes of Siberian woolly mammoths and revealed that although the mammoth population experienced a significant bottleneck — an event that significantly reduces the size and genetic diversity of a population — it recovered well. In the case of the woolly mammoths on Wrangel Island, the bottleneck event occurred when rising sea levels and changing climates caused their numbers to decline significantly as they became isolated on the island.
This drastic reduction in population size limited their genetic diversity and may have made them more susceptible to environmental stressors and changes.
The study found that the Wrangel Island mammoth population started with just eight individuals, grew to about 200 to 300, and remained stable until its extinction. Over time, the worst genetic mutations became less common because mammoths with these harmful traits reproduced less quickly.
This suggests that, contrary to expectations, inbreeding did not lead to the accumulation of deleterious mutations that could have caused their extinction. Instead, the isolated mammoth population was able to wipe out these deleterious mutations over generations, challenging the traditional view that genetic degradation was the primary factor in their demise.
Do we have anything to do with extinction?
The new genetic data for woolly mammoths suggests that inbreeding was just a small part of a larger storm brewing. While the mammoths faced genetic challenges due to their isolation, the real threats to their survival likely came from a combination of known and unknown environmental changes and, most likely, human interference.
The last woolly mammoths died out 4,000 years ago. Around this time, human civilization was making technological advances and expanding geographically. Early humans had reached several remote parts of the world, including areas near Wrangel Island.
This period marked significant changes in human hunting practices and land use, which could have had a profound impact on local ecosystems. Although direct evidence of human hunting of the last mammoths on Wrangel Island remains elusive, the coinciding timelines suggest that human activity may have played a role in depressing mammoth populations, either through direct hunting or by altering their habitats.
This hypothesis is consistent with broader patterns observed in other species extinctions, where human expansion and environmental impact have often been critical factors. A similar scenario played out with the Tasmanian tiger, which faced relentless hunting, habitat loss due to agricultural expansion, and diseases introduced by invasive species. These factors combined to lead to the inbreeding problem and subsequent extinction.
The dodo is another example of extinction due to human activity. Originally from Mauritius, the dodo was not used to predators, making it vulnerable when humans arrived. The introduction of invasive species, habitat destruction, and direct hunting by sailors led to the dodo becoming extinct by the end of the 17th century.
The dodo, once a native bird of Mauritius, was driven to premature extinction by human activity. … [+]
In both cases, as with the woolly mammoths, it was not one factor but a combination of human influences and environmental changes that led to their demise. Only time will reveal the details of how the last woolly mammoths to roam the Earth met their end, but findings like these put things into perspective for us. They remind us that most species are resilient, built to withstand a variety of challenges. Often, it takes a series of unfortunate events for a species to truly go extinct.