Four thousand years ago, the last woolly mammoth on Earth took its final breath, leaving behind a mystery that has puzzled scientists for centuries. While it was long believed that inbreeding and genetic decline led to the extinction of these majestic creatures, recent research suggests that their demise might have been caused by an entirely different factor.
These findings were published in the July 11 issue of Cell, challenging the longstanding theory that inbreeding alone could have driven these creatures to extinction. Woolly mammoths once roamed the vast expanses of mainland Siberia. However, as sea levels rose, some became stranded on islands like Wrangel, where they remained isolated from other populations. This isolation could have reduced genetic diversity, a critical factor for a species' ability to adapt to environmental changes.
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However, Dalén and his team have long questioned this idea, and their latest research provides strong evidence against it. Over the years, the team has collected woolly mammoth tusks, bones, and teeth from Siberia and Wrangel Island. They extracted and analysed the DNA from 21 of these specimens, representing the last 50,000 years of the species' existence, including the period when some mammoths became isolated on Wrangel Island.
Mammoth Tusk (Image: Canva)
Using advanced computer models, the researchers compared the mammoth genomes to those of humans and elephants, the closest living relatives of mammoths. These models helped them assess the impact of different genetic mutations on the mammoths and whether these mutations had been purged from the population over time.
The analysis revealed that Wrangel Island's mammoth population began with as few as eight individuals, eventually growing to a stable population of around 200 to 300 animals. Over time, the most harmful mutations became less common, likely because affected individuals were less likely to reproduce. Less severe mutations, according to Dalén, were unlikely to have caused the mammoths' extinction.
Vincent Lynch, an evolutionary biologist at the University at Buffalo, New York, who was not involved in the study, commented on the findings: "This data offers compelling evidence against the meltdown model, but it doesn't entirely rule it out." He suggests that while genetic variation loss may not have been the decisive factor, a gradual accumulation of minor mutations could have made the mammoths more vulnerable to other threats, such as disease, climate change, or human activity.
Reflecting on the findings, Dalén speculates, "Perhaps they were simply unlucky. If a catastrophe hadn't struck Wrangel Island, we might still have mammoths walking among us today."
Palaeontologist Joshua Miller from the University of Cincinnati, who was not part of the study, described the research as "remarkable." He noted that the new insights into the genetic history of Wrangel Island's mammoths could have broader implications for understanding extinction events and might offer valuable lessons for conserving endangered species today.
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