The woolly mammoth, a defining creature of the Ice Age, faced its final days on Wrangel Island, situated off the coast of present-day Siberia, around 4,000 years ago. For many years, scientists believed that the isolation of this last mammoth population led to genetic inbreeding, which was thought to be a key factor in their extinction. However, a recent study has challenged this longstanding notion, suggesting that breeding was not the sole cause of their demise.
Reevaluating Inbreeding and Genetic Health
A groundbreaking study published in Cell on July 11, 2024, has cast new light on the reasons behind the extinction of the woolly mammoth. Led by Dr. Love Dalén, an evolutionary geneticist at the Centre for Palaeogenetics in Stockholm, the research examined 21 complete genomes from mammoths that roamed during their final 50,000 years. Contrary to previous beliefs, the study found that while the mammoths on Wrangel Island were indeed inbred, this genetic factor alone did not lead to their extinction.
Dr. Dalén’s team discovered that over time, the mammoth herd on Wrangel Island experienced a reduction in harmful genetic mutations. This finding suggests that inbreeding may have led to the removal of detrimental mutations rather than their accumulation. Initially starting with a small population of around eight individuals, the Wrangel Island mammoths eventually grew to a population size of between 200 and 300, maintaining this number until their extinction.
Challenging the Meltdown Model
The study presents compelling evidence against the “meltdown model,” which posits that genetic isolation and inbreeding result in a gradual accumulation of harmful mutations, ultimately leading to extinction. Dr. Dalén’s findings indicate that the genetic health of the Wrangel Island mammoths may have actually improved over time, opposing the notion that inbreeding inevitably led to their demise.
Vincent Lynch, an evolutionary biologist at the University at Buffalo, acknowledges the significance of the study but also notes that it does not entirely rule out the meltdown model. He suggests that reduced genetic variation might have made the mammoths more susceptible to other threats, such as diseases, environmental changes, or human activities.
Unresolved Mysteries
Despite these new insights, the exact causes of the woolly mammoths’ extinction remain elusive. Dr. Dalén posits that unforeseen disasters or major environmental changes could have been pivotal in their final extinction. Without such catastrophic events, it is conceivable that the mammoths could have continued to survive.
The study highlights the complexity of extinction events and underscores the need for continued research to unravel the multifaceted factors contributing to the disappearance of species. While the genetic health of the Wrangel Island mammoths appears to have improved, it is clear that other factors likely played a crucial role in their ultimate extinction
