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.

Challenging the 'Meltdown Model'

The final population of woolly mammoths lived on Wrangel Island, a remote landmass off the coast of modern-day Siberia. Cut off from other mammoth populations by rising sea levels around 10,000 years ago, these isolated giants faced a limited gene pool, leading to inbreeding. While inbreeding typically results in offspring with reduced genetic diversity and a higher likelihood of harmful mutations, a new study reveals that this was not the cause of their extinction. In fact, over time, the Wrangel Island mammoths managed to shed many harmful genetic mutations, suggesting that their ultimate fate was sealed by an unforeseen event.

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.

Read More: Y chromosome disappearing slowly: Is the world moving towards a male-less future?

Insights from DNA Analysis

Love Dalén, an evolutionary geneticist at the Centre for Palaeogenetics in Stockholm, Sweden, who participated in the study, explains, "Genetic variation is essential for animals to adapt to environmental changes." Scientists had previously theorised that the loss of genetic variation due to inbreeding would lead to a buildup of harmful mutations, ultimately causing the population to decline—a concept known as the "meltdown model."

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.