Why Did Woolly Mammoths Die? Study Concludes Cause Remains a Mystery

10,000 years ago, when sea levels rose and Wrangel Island off the coast of Siberia separated from the mainland, the last population woolly mammoths – already significantly reduced by exhaustive hunting carried out over thousands of years – were isolated and, according to genomic research, these animals lived in Wrangel for another 6,000 years.

A study by Stockholm University in Sweden shows that this group of mammoths, which lived in isolation on the island for the next 6,000 years, descended from a maximum of eight individuals that grew to 200 or 300 people after 20 generations.

However, the study, whose findings were published this Thursday in the journal cellconcludes that although the genomes of mammoths Wrangel Island showed signs of inbreeding and low genetic diversity, insufficient to explain them mysterious extinction.

“What happened at the end remains a mystery: we don’t know why they died out after living more or less well for 6,000 years, but we think it happened suddenly,” says the study’s lead author. Love Dalenevolutionary geneticist at the Center for Paleogenetics.

Thanks to the results of this study, “we can confidently reject the idea that the population was simply too small and that they were doomed to extinction for genetic reasons,” emphasizes Dahlen.

“This means that they were probably killed by some random event, and if this random event had not happened, we would still have mammoths today,” the researcher says.

In addition to shedding light on woolly mammoth population dynamics, this analysis of the Wrangel Island mammoths may help develop conservation strategies for the now endangered animal.

“Mammoths are a great system for understanding the current biodiversity crisis and what happens genetically when a species experiences population problems,” says first author, Marianna Deaskfrom the Center for Paleogenetics.

Mysterious disappearance

To understand the genomic implications of the Wrangel Island bottleneck for the mammoth population, the team analyzed genomes of 21 woolly mammoths: 14 people from Wrangel Island and 7 people from the mainland population that existed before the bottleneck.

In total, the samples covered the last 50,000 years of existence woolly mammoth, which will allow us to understand how its genetic diversity has changed over time.

Compared to their continental ancestors, the genomes of Wrangel Island mammoths showed signs of inbreeding and low genetic diversity.

Moreover, they have reduced diversity in the broader complex. histocompatibilitya group of genes known to play a fundamental role in the immune response of vertebrates.

The team showed that the population’s genetic diversity continued to decline over the 6,000 years that mammoths inhabited Wrangel Island, although very slow pacewhich suggests that the population size remained stable until the end.

And although the island’s gigantic population gradually accumulated moderately harmful mutations Over the course of its 6,000 years of existence, researchers have shown that the population has slowly eliminated the most harmful mutations.

“If an individual has a mutation that’s extremely harmful, it’s essentially unviable, so those mutations would have gradually disappeared from the population over time, but on the other hand, we see that mammoths accumulated moderately harmful mutations almost until they went extinct,” Dehask says.

“It is important that current conservation programs recognize that returning the population to a decent size is not enough; “We also have to actively and genetically monitor this,” he warns.

While the mammoth genomes analyzed in this study span a wide period of time, they do not include the last 300 years of the species’ existence. However, the researchers have found fossils from the mammoth’s final period of existence and plan to conduct further research. genomic sequencing in future.

“What happened at the end remains a mystery: we don’t know why they died out after living more or less well for 6,000 years, but we think it was something sudden,” says Dalén.