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Four thousand years ago, the woolly mammoth, a prominent figure of the Ice Age, met its end on Wrangel Island, located off the coast of present-day Siberia. Historically, scientists speculated that the isolation of this last mammoth population led to genetic inbreeding, contributing to their extinction. However, new research offers a different perspective, suggesting that inbreeding was not the only factor in their demise.
Inbreeding and genetic health
A recent studyPublished in Cell on July 11, 2024, challenges the idea that genetic isolation was the primary cause of the woolly mammoths’ extinction. The research, led by Dr. Love Dalén, an evolutionary geneticist at the Centre for Palaeogenetics in Stockholm, examined 21 complete genomes of mammoths that lived during their last 50,000 years. Contrary to previous beliefs, the study found that while the Wrangel Island mammoths were inbred, this alone did not lead to their extinction.
Dr. Dalén’s team found that the Wrangel Island mammoth herd lost many of its harmful genetic mutations over time. This suggests that inbreeding may have eliminated harmful mutations rather than exacerbating them. The Wrangel Island herd, which started out as a small population of about eight individuals, eventually grew to between 200 and 300 members and remained at this size until the species’ extinction.
Challenging the Meltdown Model
The study’s findings provide significant evidence against the “meltdown model,” which suggests that genetic isolation and inbreeding lead to a gradual accumulation of harmful mutations, ultimately causing extinction. Instead, the research suggests that the mammoths may have experienced an improvement in their genetic health over time, contradicting the idea that inbreeding alone was a death sentence for the species.
Vincent Lynch, an evolutionary biologist at the University at Buffalo, notes that while the study provides strong evidence against the meltdown model, it doesn’t rule it out entirely. He suggests that reduced genetic variation could have made mammoths more vulnerable to other threats, such as disease, climate change or human encroachment.
Unsolved mysteries
Despite these revelations, the exact reasons behind the woolly mammoths’ eventual extinction remain uncertain. Dr. Dalén proposes that unforeseen disasters or significant environmental changes played a crucial role in their demise. Without such catastrophic events, it is possible that the mammoths could have continued to survive.
The study underscores the complexity of extinction events and highlights the need for continued research to fully understand the multiple factors that contribute to species disappearance. While the genetic health of the Wrangel Island mammoths appears to have improved, other factors likely played a significant role in their eventual extinction.
